17. Commitments and Contingencies

Operating Leases

As of December 31, 2014 and 2013, the Company has several non-cancelable operating leases that expire over the next six years. Minimum rent payments under operating leases are recognized on a straight-line basis over the term of the lease.

Future minimum lease payments under non-cancelable operating leases (with initial or remaining lease terms in excess of one year) as of December 31, 2014 are:

Year ending December 31,
2015	$	2,984,131
2016		3,005,307
2017		3,061,674
2018		3,122,828
2019		2,877,155
2020 and thereafter		2,526,699

Total future minimum lease payments	$	17,577,794

Rental expense and rental income for all operating leases for the years ended December 31, 2014, and 2013 were as follows:

	2014			2013
Minimum rentals	$	1,538,513		$	769,000
Sublease rental income		(63,242	)		(76,104	)

	$	1,475,271		$	692,896

Sale Leaseback transactions

Under a limited number of arrangements, the Company provides its products and services to customers in the form of an operating lease that can vary in term from five to six years. For these specific transactions, the Company will complete a sale-leaseback for the related assets to a financial institution for similar five to six year terms. The Company accounts for sale-leaseback transactions in accordance with Accounting Standards Codification (ASC) Subtopic 840-40, Leases—Sale-Leaseback Transactions.

Hydrogen Supply Agreements

The Company has entered into hydrogen supply agreements that range from six to ten years, which include monthly service charges for hydrogen maintenance, hydrogen infrastructure and hydrogen tank rentals for use at our customers' facilities.

Litigation

During the year ended December 31, 2014, the Company accrued a $2.4 million liability relating to litigation dating back to 2008 with Soroof Trading Development Company Ltd.

Concentrations of credit risk

Concentrations of credit risk with respect to receivables exist due to the limited number of select customers that the Company has initial commercial sales arrangements with and government agencies. To mitigate credit risk, the Company performs appropriate evaluation of a prospective customer's financial condition.

At December 31, 2014, four customers comprise approximately 69.9% of the total accounts receivable balance, with each customer individually representing 30.2%, 16.0%, 13.4% and 10.3% of total accounts receivable, respectively. At December 31, 2013, five customers comprise approximately 78.3% of the total accounts receivable balance, with each customer individually representing 30.8%, 26.9%, 10.2%, 5.8% and 4.6% of total accounts receivable, respectively.

For the year ended December 31, 2014, contracts with two customers comprised 37.2% of total consolidated revenues, with each customer individually representing 24.1% and 13.1% of total consolidated revenues, respectively.

For the year ended December 31, 2013, contracts with three customers comprised 33.2% of total consolidated revenues, with each customer individually representing 11.6%, 11.2% and 10.4% of total consolidated revenues, respectively.

Employment Agreements

The Company is party to employment agreements with certain executives which provide for compensation and certain other benefits. The agreements also provide for severance payments under certain circumstances.

Letter of Credit

In September 2011, the Company signed a letter of credit with SVB in the amount of $525,000. The standby letter of credit is required by the agreement negotiated between Air Products and Chemicals, Inc., or Air Products, and us to supply hydrogen infrastructure and hydrogen to Central Grocers at their distribution center. There are no collateral requirements associated with this letter of credit.