7. Commitments and Contingencies Operating Leases The Company rents its office and laboratory facilities in Mountain View, California under an operating lease which has been extended until January 2020, with an option to extend the lease for another five years. The Company also leases approximately 3,300 square feet of office space in London, England, lease of which ends in June 2020. As of December 31, 2014, the Company has exercised the option to exit the London lease in 2015 and incurred $0.1 million exit cost recorded on the consolidated statement of operations. The Company s London s office is currently in the process of locating a smaller office space. Rent expense on a straight-line basis was as follows (in thousands): Years Ended December 31, 2014 2013 2012 Rent expense $ 2,613 $ 2,310 $ 2,280 At December 31, 2014, future minimum payments under the leases are as follows (in thousands): Years ended December 31, Future Minimum Lease Payments 2015 $ 2,162 2016 2,141 2017 2,205 2018 2,271 2019 2,144 Thereafter   Total $ 10,923 Warranties The Company generally provides one year of post-contract customer service on the sale of its systems. Post-contract customer service revenue is recognized ratably over the term of the service period and associated expenses are charged to cost of revenues as incurred. The Company provides a limited warranty on the sale of robotic systems and records a warranty reserve at the time of sale to cover the estimated warranty costs. The Company s warranty obligation may be impacted by product failure rates, material usage and service costs associated with its warranty obligations. The Company periodically evaluates and adjusts the warranty reserve to the extent actual warranty expense differs from the original estimates. Movement in the warranty liability have not been significant for the years ended December 31, 2014 and 2013, respectively. Other Royalty Obligations The Company has minimum royalty obligations of $100,000 per year under a license agreement with Mitsubishi Electric Re