Property, Plant and Equipment, Net

As of December 31, 2015 and 2014, the components of property, plant and equipment are stated at cost less accumulated depreciation as follows (in millions):



	2015		2014		Depreciable Lives
Buildings, machinery and equipment	$	16,294	$	16,059	3 – 47 Years
Geothermal properties	1,319		1,294		13 – 58 Years
Other	208		203		3 – 47 Years
	17,821		17,556
Less: Accumulated depreciation	5,377		4,984
	12,444		12,572
Land	120		120
Construction in progress	448		498
Property, plant and equipment, net	$	13,012	$	13,190

Total depreciation expense, including amortization of leased assets, recorded for the years ended December 31, 2015, 2014 and 2013, was $595 million, $591 million and $584 million, respectively.

We have various debt instruments that are collateralized by our property, plant and equipment. See Note 6 for a discussion of such instruments.

Buildings, Machinery and Equipment

This component primarily includes power plants and related equipment. Included in buildings, machinery and equipment are assets under capital leases. See Note 6 for further information regarding these assets under capital leases.

Geothermal Properties

This component primarily includes power plants and related equipment associated with our Geysers Assets.

Other

This component primarily includes software and emission reduction credits that are power plant specific and not available to be sold.

Capitalized Interest

The total amount of interest capitalized was $15 million, $19 million and $38 million for the years ended December 31, 2015, 2014 and 2013, respectively.