Property, Plant and Equipment, Net

As of December 31, 2016 and 2015, the components of property, plant and equipment are stated at cost less accumulated depreciation as follows (in millions):



	2016		2015		Depreciable Lives
Buildings, machinery and equipment	$	16,468	$	16,294	3 – 46 Years
Geothermal properties	1,377		1,319		13 – 58 Years
Other	259		208		3 – 46 Years
	18,104		17,821
Less: Accumulated depreciation	5,865		5,377
	12,239		12,444
Land	116		120
Construction in progress	658		448
Property, plant and equipment, net	$	13,013	$	13,012

Total depreciation expense, including amortization of leased assets, recorded for the years ended December 31, 2016, 2015 and 2014, was $628 million, $595 million and $591 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 $21 million, $15 million and $19 million for the years ended December 31, 2016, 2015 and 2014, respectively.