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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q

x      Quarterly Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

For the quarterly period ended March 31, 2013.

o         Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

For the transition period from                      to                     .

Commission file number: 001-34877

CoreSite Realty Corporation

(Exact name of registrant as specified in its charter)

(866) 777-2673

(Registrant’s telephone number, including area code)

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes x No o.

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files). Yes x No o

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes o No x

The number of shares of common stock outstanding at April 23, 2013 was 21,381,336.

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CORESITE REALTY CORPORATION
FORM 10-Q
FOR THE QUARTER ENDED MARCH 31, 2013
TABLE OF CONTENTS

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PART I — FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

CORESITE REALTY CORPORATION

CONDENSED CONSOLIDATED BALANCE SHEETS

(unaudited and in thousands except share data)

See accompanying notes to condensed consolidated financial statements.

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CORESITE REALTY CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(unaudited and in thousands except share and per share data)

See accompanying notes to condensed consolidated financial statements.

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CORESITE REALTY CORPORATION

CONDENSED CONSOLIDATED STATEMENT OF EQUITY

(unaudited and in thousands except share data)

See accompanying notes to condensed consolidated financial statements.

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CORESITE REALTY CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(unaudited and in thousands)

See accompanying notes to condensed consolidated financial statements.

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CORESITE REALTY CORPORATION

NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

March 31, 2013

(unaudited)

1. Organization and Description of Business

CoreSite Realty Corporation, through its controlling interest in CoreSite, L.P. (the “Operating Partnership”) and the subsidiaries of the Operating Partnership (collectively, the “Company,” “we,” or “our”), is a fully-integrated, self-administered, and self-managed real estate investment trust (“REIT”). The Company was organized in the State of Maryland on February 17, 2010, completed its initial public offering of common stock (the “IPO”) on September 28, 2010, and is the sole general partner of the Operating Partnership. As of March 31, 2013, the Company owns a 45.0% common interest in the Operating Partnership.

We are engaged in the business of owning, acquiring, constructing and managing technology-related real estate and as of March 31, 2013, our property portfolio included 14 operating data center facilities and multiple development projects located in some of the largest and fastest growing data center markets in the United States, including Los Angeles, the San Francisco Bay and Northern Virginia, Chicago, Boston, New York City, Miami and Denver. The development projects include construction of new facilities in the San Francisco Bay, Northern Virginia, and New York.

2. Summary of Significant Accounting Policies

Principles of Consolidation and Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared by management in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and in compliance with the rules and regulations of the United States Securities and Exchange Commission. Accordingly, these condensed consolidated financial statements do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. The results of operations for the three months ended March 31, 2013, are not necessarily indicative of the expected results for the year ending December 31, 2013. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2012. Intercompany balances and transactions have been eliminated.

Use of Estimates

The preparation of these condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingencies at the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. We evaluate our estimates, including those related to assessing the carrying values of our real estate properties, accrued liabilities, and performance-based equity compensation plans. We base our estimates on historical experience, current market conditions, and various other assumptions that we believe to be reasonable under the circumstances. Actual results may vary from those estimates and those estimates could vary under different assumptions or conditions.

Adjustments and Reclassifications

Cash used for tenant improvement investing activities, included in the accompanying condensed consolidated statement of cash flows for 2012 have been reclassified to conform to the 2013 presentation. In addition, certain other amounts included in the condensed consolidated financial statements for 2012 have been reclassified to conform to the 2013 financial statement presentation.

Investments in Real Estate

Real estate investments are carried at cost less accumulated depreciation and amortization. The cost of real estate includes the purchase price of the property and leasehold improvements. Expenditures for maintenance and repairs are expensed as incurred. Significant renovations and betterments that extend the economic useful lives of assets are capitalized. During the land development and construction periods, we capitalize construction costs, legal fees, financing costs, real estate taxes and insurance and internal costs of personnel performing development, if such costs are incremental and identifiable to a specific development project. Capitalization begins upon commencement of development efforts and ceases when the property is ready for its intended use and held available for occupancy. Interest is capitalized during the period of development based upon applying the weighted-average borrowing rate to the actual development costs expended. Capitalized interest costs were $0.9 million and $0.7 million for the three months ended March 31, 2013, and 2012, respectively.

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Depreciation and amortization are calculated using the straight-line method over the following useful lives of the assets:

Depreciation expense was $11.9 million and $9.4 million for the three months ended March 31, 2013, and 2012, respectively.

Acquisition of Investment in Real Estate

Purchase accounting is applied to the assets and liabilities related to all real estate investments acquired. The fair value of the real estate acquired is allocated to the acquired tangible assets, consisting primarily of land, building and improvements, and identified intangible assets and liabilities, consisting of the value of above-market and below-market leases, value of in-place leases and the value of customer relationships.

The fair value of the land and building of an acquired property is determined by valuing the property as if it were vacant, and the “as-if-vacant” value is then allocated to land and building based on management’s determination of the fair values of these assets. Management determines the as-if-vacant fair value of a property using methods similar to those used by independent appraisers. Factors considered by management in performing these analyses include an estimate of carrying costs during the expected lease-up periods considering current market conditions and costs to execute similar leases.

The fair value of intangibles related to in-place leases includes the value of lease intangibles for above-market and below-market leases, lease origination costs, and customer relationships, determined on a lease-by-lease basis. Above-market and below-market leases are valued based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between (i) the contractual amounts to be paid pursuant to the in-place leases and (ii) management’s estimate of fair market lease rates for the corresponding in-place leases, measured over a period equal to the remaining non-cancelable term of the lease and, for below-market leases, over a period equal to the initial term plus any below-market fixed rate renewal periods. Lease origination costs include estimates of costs avoided associated with leasing the property, including tenant allowances and improvements and leasing commissions. Customer relationship intangibles relate to the additional revenue opportunities expected to be generated through interconnection services and utility services to be provided to the in-place lease tenants.

The capitalized values for above and below-market lease intangibles, lease origination costs, and customer relationships are amortized over the term of the underlying leases or the expected customer relationship. Amortization related to above-market and below-market leases where the Company is the lessor is recorded as either a reduction of or an increase to rental income, amortization related to above-market and below-market leases where the Company is the lessee is recorded as either a reduction of or an increase to rent expense and amortization for lease origination costs and customer relationships are recorded as amortization expense. If a lease is terminated prior to its stated expiration, all unamortized amounts relating to that lease are written off. The carrying value of intangible assets is reviewed for impairment in connection with its respective asset group whenever events or changes in circumstances indicate that the asset group may not be recoverable. An impairment loss is recognized if the carrying amount of the asset group is not recoverable and its carrying amount exceeds its estimated fair value. No impairment loss was recognized for the three months ended March 31, 2013.

The excess of the cost of an acquired business over the net of the amounts assigned to assets acquired (including identified intangible assets) and liabilities assumed is recorded as goodwill. As of March 31, 2013, and December 31, 2012, we had approximately $41.2 million of goodwill at each date. The Company’s goodwill has an indeterminate life and is not amortized, but is tested for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that the asset might be impaired. No impairment loss was recognized for the three months ended March 31, 2013.

Cash and Cash Equivalents

Cash and cash equivalents include all non-restricted cash held in financial institutions and other non-restricted highly liquid short-term investments with original maturities at acquisition of three months or less.

Deferred Costs

Deferred leasing costs include commissions and other direct and incremental costs incurred to obtain new customer leases, which are capitalized and amortized over the terms of the related leases using the straight-line method. If a lease terminates prior to the expiration of its initial term, any unamortized costs related to the lease are written off to amortization expense.

Deferred financing costs include costs incurred in connection with obtaining debt and extending existing debt. These financing costs are capitalized and amortized on a straight-line basis, which approximates the effective-interest method, over the term of the loan and are included as a component of interest expense.

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Recoverability of Long-Lived Assets

The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Impairment is recognized when estimated expected future cash flows (undiscounted and without interest charges) are less than the carrying amount of the assets. The estimation of expected future net cash flows is inherently uncertain and relies, to a considerable extent, on assumptions regarding current and future economics and market conditions and the availability of capital. If, in future periods, there are changes in the estimates or assumptions incorporated into the impairment review analysis, the changes could result in an adjustment to the carrying amount of the assets. To the extent that an impairment has occurred, the excess of the carrying amount of long-lived assets over its estimated fair value would be charged to income. For the three months ended March 31, 2013, and 2012, no impairment was recognized.

Revenue Recognition

All leases are classified as operating leases and minimum rents are recognized on a straight-line basis over the non-cancellable term of the agreements. The excess of rents recognized over amounts contractually due pursuant to the underlying leases are included in deferred rent receivable. If a lease terminates prior to its stated expiration, the deferred rent receivable relating to that lease is written off as a reduction of rental revenue.

When arrangements include both lease and nonlease elements, the revenue associated with separate elements are allocated based on their relative fair values. The revenue associated with each element is then recognized as earned. Interconnection, utility and power services are considered as separate earnings processes that are provided and completed on a month-to-month basis and revenue is recognized in the period that services are performed. Utility and power services are included in power revenue in the accompanying condensed consolidated statements of operations. Set-up charges and utility installation fees are initially deferred and recognized over the term of the arrangement as revenue or the expected period of performance unless management determines a separate earnings process exists related to an installation charge.

Tenant reimbursements for real estate taxes, common area maintenance, and other recoverable costs are recognized in the period that the expenses are incurred.

Above-market and below-market lease intangibles that were acquired are amortized on a straight-line basis as decreases and increases, respectively, to rental revenue over the remaining non-cancellable term of the underlying leases. For the three months ended March 31, 2013, and 2012, the net effect of amortization of acquired above-market and below-market leases resulted in an increase to rental revenue of $0.2 million and $0.4 million, respectively.

A provision for uncollectible accounts is recorded if a receivable balance relating to contractual rent, rent recorded on a straight-line basis, or tenant reimbursements is considered by management to be uncollectible. At March 31, 2013, and December 31, 2012, the allowance for doubtful accounts totaled $0.6 million for each period.

Share-Based Compensation

We account for share-based compensation using the fair value method of accounting. The estimated fair value of the stock options granted by us is amortized on a straight-line basis over the vesting period. The fair value of restricted share-based and Operating Partnership unit compensation is based on the market value of our common stock on the date of the grant and is amortized on a straight-line basis over the vesting period.

Asset Retirement and Environmental Remediation Obligations

We record accruals for estimated retirement and environmental remediation obligations. The obligations relate primarily to the removal of asbestos and contaminated soil during development of the properties as well as the estimated equipment removal costs upon termination of a certain lease where the Company is the lessee. At March 31, 2013, and December 31, 2012, the amount included in other liabilities on the condensed consolidated balance sheets was approximately $2.7 million and $2.6 million, respectively.

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Income Taxes

We elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended (the “Code”), commencing with our taxable year ended December 31, 2010. To qualify as a REIT, we are required to distribute at least 90% of our taxable income to our stockholders and meet various other requirements imposed by the Code relating to such matters as operating results, asset holdings, distribution levels and diversity of stock ownership. Provided we qualify for taxation as a REIT, we are generally not subject to corporate level federal income tax on the earnings distributed currently to our stockholders. If we fail to qualify as a REIT in any taxable year, and are unable to avail ourselves of certain savings provisions set forth in the Code, all of our taxable income would be subject to federal income tax at regular corporate rates, including any applicable alternative minimum tax.

To maintain REIT status, we must distribute a minimum of 90% of our taxable income. However, it is our policy and intent, subject to change, to distribute 100% of our taxable income and therefore no provision is required in the accompanying financial statements for federal income taxes with regards to activities of the REIT and its subsidiary pass-through entities. Any taxable income prior to the completion of the IPO is the responsibility of the Company’s prior member. The allocable share of income is included in the income tax returns of the members. The Company is subject to the statutory requirements of the locations in which it conducts business. State and local income taxes are accrued as deemed required in the best judgment of management based on analysis and interpretation of respective tax laws.

We have elected to treat two of our subsidiaries as taxable REIT subsidiaries (“TRS”). Certain activities that we undertake must be conducted by a TRS, such as services for our tenants that could be considered otherwise impermissible for us to perform and holding assets that we cannot hold directly. A TRS is subject to corporate level federal and state income taxes. Relative deferred tax assets and liabilities arising from temporary differences in financial reporting versus tax reporting are also established as determined by management.

Deferred income taxes are recognized in certain taxable entities. Deferred income tax is generally a function of the period’s temporary differences (items that are treated differently for tax purposes than for financial reporting purposes), the utilization of tax net operating losses generated in prior years that previously had been recognized as deferred income tax assets and the reversal of any previously recorded deferred income tax liabilities. A valuation allowance for deferred income tax assets is provided if we believe all or some portion of the deferred income tax asset may not be realized. Any increase or decrease in the valuation allowance resulting from a change in circumstances that causes a change in the estimated realizability of the related deferred income tax asset is included in deferred tax expense. As of March 31, 2013, the deferred income taxes were not material.

We currently have no liabilities for uncertain tax positions. The earliest tax year for which we are subject to examination is 2010. Prior to their contribution to our Operating Partnership, our subsidiaries were treated as pass-through entities for tax purposes and the earliest year for which our subsidiaries are subject to examination is 2009.

Concentration of Credit Risks

Our cash and cash equivalents are maintained in various financial institutions, which, at times, may exceed federally insured limits. The Company has not experienced any losses in such accounts, and management believes that the Company is not exposed to any significant credit risk in this area. We have no off-balance-sheet concentrations of credit risk, such as foreign exchange contracts, option contracts, or foreign currency hedging arrangements.

For the three months ended March 31, 2013, and 2012, one customer accounted for 7.3% and 10.4%, respectively, of total operating revenues.

Segment Information

We manage our business as one reportable segment consisting of investments in data centers located in the United States. Although we provide services in several markets, these operations have been aggregated into one reportable segment based on the similar economic characteristics amongst all markets, including the nature of the services provided and the type of customers purchasing these services.

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3. Investment in Real Estate

On February 7, 2013, the Company acquired land and a vacant building, NY2, in Secaucus, NJ, with a total real estate value of $23.0 million.  NY2 is being developed into a data center facility. During the three months ended March 31, 2013, in addition to NY2, the Company commenced development on two other data center facilities, VA2 and SV5. Based on the relative fair values of each data center and the current land balances, land was allocated to each of VA2 and SV5 and was reclassified during the first quarter of 2013 to construction in progress in the condensed consolidated balance sheet. The reclassification equaled $5.2 million and $2.4 million for VA2 and SV5, respectively.

The following is a summary of the properties owned and leased at March 31, 2013 (in thousands):

4. Other Assets

Our other assets consisted of the following, net of amortization and depreciation, if applicable, as of March 31, 2013, and December 31, 2012 (in thousands):

Deferred leasing costs are amortized as amortization expense on a straight-line basis over the remaining life of the underlying leases.  The estimated amortization of deferred leasing costs for each of the five succeeding fiscal years is as follows (in thousands):

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5. Debt

A summary of outstanding indebtedness as of March 31, 2013, and December 31, 2012 is as follows (in thousands):

Revolving Credit Facility

On January 3, 2013, our Operating Partnership and certain subsidiary co-borrowers entered into a second amended and restated senior unsecured revolving credit facility (the “Second Amended and Restated Credit Agreement”) with a group of lenders for which KeyBank National Association acts as administrative agent. The Second Amended and Restated Credit Agreement amended the Operating Partnership’s senior secured revolving credit facility, dated December 15, 2011 (the “Prior Facility”), and provides for the release of the properties owned by the Operating Partnership’s wholly-owned subsidiaries from the existing liens in favor of the credit facility lenders, with the facility continuing on an unsecured basis and unconditionally guaranteed on a senior unsecured basis by the Company. Our Operating Partnership acts as the parent borrower, and our subsidiaries that own or lease real estate properties, are co-borrowers under the Second Amended and Restated Credit Agreement.

The Second Amended and Restated Credit Agreement increased the commitment from the Prior Facility of $225.0 million to $355.0 million and extended the initial maturity date of the Prior Facility from December 15, 2014, to January 3, 2017, with a one-time extension option, which, if exercised, would extend the maturity date to January 3, 2018. The exercise of the extension option is subject to the payment of an extension fee equal to 25 basis points of the total commitment under the Second Amended and Restated Credit Agreement at initial maturity and certain other customary conditions. The Second Amended and Restated Credit Agreement contains an accordion feature, which allows our Operating Partnership to increase the total commitment by $145.0 million, to $500.0 million, under specified circumstances. As of March 31, 2013, and December 31, 2012, $52.0 and $0 million, respectively, was outstanding under the facility.

Under the Second Amended and Restated Credit Agreement, our Operating Partnership may elect to have borrowings bear interest at a rate per annum equal to (i) LIBOR plus 200 basis points to 275 basis points, or (ii) a base rate plus 100 basis points to 175 basis points, each depending on our Operating Partnership’s leverage ratio.

The total amount available for borrowings under the Second Amended and Restated Credit Agreement will be subject to the lesser of the facility amount or the availability calculated on our unencumbered asset pool. As of March 31, 2013, $294.5 million was available for us to borrow under the Second Amended and Restated Credit Agreement.

Our ability to borrow under the Second Amended and Restated Credit Agreement is subject to ongoing compliance with a number of financial covenants and other customary restrictive covenants, including, among others:

·                  a maximum leverage ratio (defined as consolidated total indebtedness to total gross asset value) of 60%;

·                  a maximum secured debt ratio (defined as consolidated total secured debt to total gross asset value) of 40%;

·                  a minimum fixed charge coverage ratio (defined as adjusted consolidated earnings before interest, taxes, depreciation and amortization to consolidated fixed charges) of 1.75 to 1.0; and

·                  a maximum unhedged variable rate debt ratio (defined as unhedged variable rate indebtedness to gross asset value) of 30%.

As of March 31, 2013, we were in compliance with the covenants under our Second Amended and Restated Credit Agreement.

SV1 Mortgage Loan

As of March 31, 2013, SV1 had a $59.4 million mortgage loan with a maturity date of October 9, 2014. The loan bears variable interest and requires the payment of interest and principal until maturity. The mortgage requires ongoing compliance by us with various covenants including liquidity and net operating income covenants. As of March 31, 2013, we were in compliance with the covenants.

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Debt Maturities

The following table summarizes the amount of our debt maturities when such debt currently becomes due (in thousands):

6. Noncontrolling Interests — Operating Partnership

Noncontrolling interests represent the limited partnership interests in the Operating Partnership held by individuals and entities other than CoreSite Realty Corporation. Since September 28, 2011, the current holders of Common Operating Partnership units have been eligible to have the Common Operating Partnership units redeemed for cash or, at our option, exchangeable into our common stock on a one-for-one basis. We have evaluated whether we control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the share settlement of the Common Operating Partnership units. Based on the results of this analysis, we concluded that the Common Operating Partnership units met the criteria to be classified within equity at March 31, 2013.

The following table shows the ownership interest in the Operating Partnership as of March 31, 2013, and December 31, 2012:

For each share of common stock issued by the Company, the Operating Partnership issues an equivalent Common Operating Partnership unit to the Company. During the three months ended March 31, 2013, the Company issued 109,234 shares of common stock related to employee compensation arrangements and, therefore, an equivalent number of Common Operating Partnership units were issued.

On December 12, 2012, the Operating Partnership issued 4.6 million Preferred Operating Partnership units to CoreSite Realty Corporation in connection with our issuance of Series A Cumulative Preferred Stock. The Preferred Operating Partnership units rank senior to the Common Operating Partnership units held by the Company and noncontrolling interests.

The redemption value of the noncontrolling interests at March 31, 2013, was $886.9 million based on the closing price of the Company’s stock of $34.98 on March 28, 2013, the last trading day of the quarter.

7. Stockholders’ Equity

On March 5, 2013, we declared a regular cash dividend for the quarter ended March 31, 2013, of $0.27 per common share payable to stockholders of record as of March 28, 2013. In addition, holders of Common Operating Partnership units also received a distribution of $0.27 per unit. The dividend and distribution were paid on April 15, 2013.

On March 5, 2013, we also declared a regular cash dividend for the quarter ended of March 31, 2013, of $0.62 per share of Series A Cumulative Redeemable Preferred Stock for the period December 12, 2012, to April 14, 2013. The dividend was paid on April 15, 2013, to stockholders of record as of March 28, 2013.

8. Equity Incentive Plan

In connection with our IPO, the Company’s Board of Directors adopted the 2010 Equity Incentive Plan (the “2010 Plan”). The 2010 Plan is administered by the Board of Directors, or the plan administrator. Awards issuable under the 2010 Plan include common stock, stock options, restricted stock, stock appreciation rights, dividend equivalents and other incentive awards. We have reserved a total of 3,000,000 shares of our common stock for issuance pursuant to the 2010 Plan, which may be adjusted for changes in our capitalization and certain corporate transactions. To the extent that an award expires, terminates or lapses, or an award is settled in cash without the delivery of shares of common stock to the participant, then any unexercised shares subject to the award will be available for future grant or sale under the 2010 Plan. Shares of restricted stock which are forfeited or repurchased by us pursuant to the 2010 Plan may again be optioned, granted or awarded under the 2010

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Plan. The payment of dividend equivalents in cash in conjunction with any outstanding awards will not be counted against the shares available for issuance under the 2010 Plan.

As of March 31, 2013, 618,326 shares of our common stock remained available for issuance pursuant to the 2010 Plan.

Stock Options

Stock option awards are granted with an exercise price equal to the closing market price of the Company’s common stock at the date of grant. The fair value of each option granted under the 2010 Plan is estimated on the date of grant using the Black-Scholes option-pricing model. For the three months ended March 31, 2013, options to purchase 208,198 shares of common stock were granted. The fair values are being expensed on a straight-line basis over the vesting periods.

The following table sets forth the stock option activity under the 2010 Plan for the three months ended March 31, 2013:

The following table sets forth the number of shares subject to options that are unvested as of March 31, 2013, and the fair value of these options at the grant date:

As of March 31, 2013, total unearned compensation on options was approximately $5.0 million, and the weighted-average vesting period was 2.6 years.

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Restricted Awards

During the three months ended March 31, 2013, the Company granted 174,952 shares of restricted stock. Additionally, the Company granted 240 restricted stock units, or RSUs. The principal difference between these instruments is that RSUs are not outstanding shares of the Company’s common stock and do not have any of the rights or privileges thereof, including voting rights. On the applicable vesting date, the holder of an RSU becomes entitled to one share of common stock for each RSU. Restricted awards are amortized on a straight-line basis over the vesting period. The following table sets forth the number of unvested restricted awards and the weighted average fair value of these awards at the date of grant:

As of March 31, 2013, total unearned compensation on restricted awards was approximately $13.8 million, and the weighted-average vesting period was 2.7 years.

Common Operating Partnership Units

In connection with our IPO, we granted 25,883 Common Operating Partnership units, which had a grant date fair value of $15.98 per unit, or $0.4 million in total. The Common Operating Partnership units are amortized on a straight-line basis over the vesting period. As of March 31, 2013, 17,254 units have vested, 7,138 units were unvested and 1,491 were forfeited. As of March 31, 2013, total unearned compensation on Common Operating Partnership units was approximately $0.1 million, and the weighted-average vesting period was less than one year.

9. Earnings Per Share

The following is a summary of basic and diluted income per share (in thousands, except share and per share amounts):

In the calculations above, we have excluded weighted average potentially dilutive securities of 133,166 and 23,806 for the three months ended March 31, 2013, and 2012, respectively, as their effect would have been antidilutive.

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10. Estimated Fair Value of Financial Instruments

Authoritative guidance issued by FASB establishes a hierarchy of valuation techniques based on the observability of inputs utilized in measuring assets and liabilities at fair values. This hierarchy establishes market-based or observable inputs as the preferred source of values, followed by valuation models using management assumptions in the absence of market inputs. The three levels of the hierarchy under the authoritative guidance are as follows:

Level 1 — Inputs are quoted prices in active markets for identical assets or liabilities.

Level 2 — Inputs are quoted prices for similar assets or liabilities in an active market, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable, and market-corroborated inputs which are derived principally from or corroborated by observable market data.

Level 3 — Inputs are derived from valuation techniques in which one or more significant inputs or value drivers are unobservable.

Our financial instruments consist of cash and cash equivalents, restricted cash, accounts and other receivables, revolving credit facility, mortgage loans payable, interest payable and accounts payable. The carrying values of cash and cash equivalents, restricted cash, accounts and other receivables, interest payable and accounts payable approximate fair values due to the short-term nature of these accounts.

The balance of our mortgage loan payable and revolving credit facility was $111.4 million and $59.8 million as of March 31, 2013, and December 31, 2012, respectively, with a fair value that approximated book value at both periods, based on Level 3 inputs from the fair value hierarchy. Under the discounted cash flow method, the fair values of mortgage notes payable and the revolving credit facility are based on the Company’s assumptions of interest rates and terms available incorporating the Company’s credit risk.

11. Related Party Transactions

We lease 1,515 net rentable square feet of space at VA1 to an affiliate of The Carlyle Group. The lease commenced on July 1, 2008, and expires on June 30, 2013. Rental revenue was less than $0.1 million for both the three months ended March 31, 2013, and 2012.

12. Commitments and Contingencies

As of March 31, 2013, the Company leases data center space under noncancelable operating lease agreements at NY1, LA1, DC1, DE1, and DE2, and the Company leases its headquarters located in Denver, Colorado, under a noncancelable operating lease agreement. The lease agreements provide for base rental rate increases at defined intervals during the term of the lease. In addition, the Company has negotiated rent abatement periods to better match the phased build-out of the data center space. The Company accounts for such abatements and increasing base rentals using the straight-line method over the noncancelable term of the lease. The difference between the straight-line expense and the cash payment is recorded as deferred rent payable.

Additionally, the Company has commitments related to telecommunications capacity used to connect data centers located within the same market or geographical area and power usage. The following table summarizes our contractual obligations as of March 31, 2013 (in thousands):

(1) Includes $52.0 million outstanding and estimated annual interest payments assuming no draws or payments on the revolving credit facility through the maturity date of January 3, 2017. The revolving credit facility is subject to variable rates and we estimated payments based on the interest rate as of March 31, 2013.

(2) Includes $59.4 million of mortgage principal payments and annual interest payments until debt maturity of $1.6 million in 2013 and $1.6 million in 2014. The mortgage payable is subject to variable rates and we estimated payments based on the interest rate as of March 31, 2013.

(3) Obligations for construction contracts for properties under construction, tenant related capital expenditures, and other capital improvements.

(4) Obligations for power contracts and telecommunications leases.

Rent expense on operating leases for the three months ended March 31, 2013, and 2012 was $4.8 million and $4.6 million, respectively.

From time to time, we are party to a variety of legal proceedings arising in the ordinary course of business. We believe that, with respect to any such matters to which we currently are a party, the ultimate disposition of any such matter will not result in a material adverse effect on us.

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Forward-Looking Statements

This Quarterly Report on Form 10-Q (this “Quarterly Report”), together with other statements and information publicly disseminated by our company, contains certain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). We intend such forward-looking statements to be covered by the safe harbor provisions for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995 and include this statement for purposes of complying with these safe harbor provisions.

In particular, statements pertaining to our capital resources, portfolio performance, financial condition and results of operations contain certain forward-looking statements. You can identify forward-looking statements by the use of forward-looking terminology such as “believes,” “expects,” “may,” “will,” “should,” “seeks,” “intends,” “plans,” “pro forma” or “anticipates” or the negative of these words and phrases or similar words or phrases that are predictions of or indicate future events or trends and that do not relate solely to historical matters. You can also identify forward-looking statements by discussions of strategy, plans or intentions. Such statements are subject to risks, uncertainties and assumptions and are not guarantees of future performance, which may be affected by known and unknown risks, trends, uncertainties and factors that are beyond our control. Should one or more of these risks or uncertainties materialize, or should underlying assumptions prove incorrect, actual results may vary materially from those anticipated, estimated or projected. The following factors, among others, could cause actual results and future events to differ materially from those set forth or contemplated in the forward-looking statements: (i) the geographic concentration of our data centers in certain markets and any adverse developments in local economic conditions or the demand for data center space in these markets; (ii) fluctuations in interest rates and increased operating costs; (iii) difficulties in identifying properties to acquire and completing acquisitions; (iv) the significant competition in our industry and an inability to lease vacant space, renew existing leases or release space as leases expire; (v) lack of sufficient customer demand to realize expected returns on our investments to expand our property portfolio; (vi) decreased revenue from costs and disruptions associated with any failure of our physical infrastructure or services; (vii) our ability to lease available space to existing or new customers; (viii) our failure to obtain necessary outside financing; (ix) our failure to qualify or maintain our status as a REIT; (x) financial market fluctuations; (xi) changes in real estate and zoning laws and increases in real property tax rates; (xii) delays or disruptions in third-party network connectivity; (xiii) service failures or price increases by third party power suppliers; (xiv) inability to renew net leases on the data center properties we lease; and (xv) other factors affecting the real estate industry generally.

While forward-looking statements reflect our good faith beliefs, they are not guarantees of future performance. We disclaim any obligation to publicly update or revise any forward-looking statement to reflect changes in underlying assumptions or factors, of new information, data or methods, future events or other changes. The risks included here are not exhaustive, and additional factors could adversely affect our business and financial performance, including factors and risks included in other sections of this Quarterly Report. Additional information concerning these and other risks and uncertainties is contained in our other periodic filings with the United States Securities and Exchange Commission, or SEC, pursuant to the Exchange Act. We discussed a number of material risks in Item 1A. “Risk Factors” of our Annual Report on Form 10-K for the year ended December 31, 2012. Those risks continue to be relevant to our performance and financial condition. Given these risks and uncertainties, investors should not place undue reliance on forward-looking statements as a prediction of actual results.

Overview

Unless the context requires otherwise, references in this Quarterly Report to “we,” “our,” “us” and “our company” refer to CoreSite Realty Corporation, a Maryland corporation, together with its consolidated subsidiaries, including CoreSite, L.P., a Delaware limited partnership of which CoreSite Realty Corporation is the sole general partner and which we refer to in this Quarterly Report as our “Operating Partnership” and CoreSite Services, Inc., a Delaware corporation, our taxable REIT subsidiary, or “TRS”.

We provide data center solutions to more than 750 of the world’s leading carriers and mobile operators, content and cloud providers, media and entertainment companies and global enterprises. Across 14 high-performance data center campuses in nine North America markets, we connect customers to help them grow their businesses, run performance-sensitive applications and secure their crucial data devices.

We formed CoreSite Realty Corporation as a Maryland corporation on February 17, 2010. We completed our IPO of common stock on September 28, 2010, and through our controlling interest in our Operating Partnership, we are engaged in the business of ownership, acquisition, construction and management of strategically located data centers in some of the largest and fastest growing data center markets in the United States, including Los Angeles, the San Francisco Bay and Northern Virginia areas, Chicago, Boston, New York City, Miami and Denver. Our high-quality data centers feature ample and redundant power, advanced cooling and security systems and many are points of dense network interconnection. We have elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended (the “Code”), commencing with our taxable year ended December 31, 2010.

Our Portfolio

As of March 31, 2013, our property portfolio included 14 operating data center facilities and multiple development projects which collectively comprise over 2.7 million net rentable square feet of space (“NRSF”), of which approximately 1.3 million NRSF is existing data center space, including pre-stabilized space. The development projects include construction of new facilities in the San Francisco Bay, Northern Virginia,

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and New York.  The operating portfolio includes approximately 324,000 NRSF of space readily available for lease, of which 245,000 NRSF is available for lease as data center space. Including the space currently under construction or in preconstruction at March 31, 2013, vacant space and land targeted for future development, we own land and buildings sufficient to develop approximately 1.2 million square feet of data center space. We expect that this development potential plus any potential expansion into new markets will enable us to accommodate existing and future customer demand and position us to significantly increase our cash flows. We intend to pursue development projects and expansion into new markets when we believe those opportunities support the additional supply in those markets. The following table provides an overview of our properties as of March 31, 2013: