16. Commitments

We have commitments under various operating leases with initial terms greater than one year for machinery and facilities. These leases have terms that will expire on various dates through 2025. We expect that in the normal course of business, these leases will be renewed or replaced by other leases. Rent expense for operating leases that provide for periodic rent escalations or rent holidays over the term of the lease is recognized on a straight-line basis. We also have commitments to purchase minimum volumes of refined product from Western under our Commercial Agreements with Western.

The following table presents our annual minimum rental payments under non-cancelable operating leases that have lease terms of one year or more (in thousands) as of March 31, 2015:



Remaining 2015	$	6,280
2016	6,969
2017	4,769
2018	2,030
2019	680
2020 and thereafter	325
	$	21,053

Total rental expense was $2.3 million and $2.1 million for the three months ended March 31, 2015 and 2014, respectively. Contingent rentals and subleases were not significant in any year.