Property, Plant and Equipment, Net

As of December 31, 2018 and 2017, the components of property, plant and equipment are stated at cost less accumulated depreciation as follows (in millions):



	2018		2017		Depreciable Lives
Buildings, machinery and equipment	$	16,400	$	16,506	1.5 – 46 Years
Geothermal properties	1,501		1,494		13 – 58 Years
Other	286		236		3 – 46 Years
	18,187		18,236
Less: Accumulated depreciation	6,832		6,383
	11,355		11,853
Land	121		117
Construction in progress	966		754
Property, plant and equipment, net	$	12,442	$	12,724

Total depreciation expense, including amortization of capital lease assets, recorded for the years ended December 31, 2018, 2017 and 2016, was $684 million, $638 million and $628 million, respectively.

We have various debt instruments that are collateralized by our property, plant and equipment. See Note 8 for a discussion of such instruments.

Depreciable Lives — During the fourth quarter of 2017, we reviewed our accounting policies related to depreciation associated with our estimates of useful lives related to our componentized balance of plant parts. During the first quarter of 2018, we reviewed our accounting policies related to depreciation associated with our estimates of useful lives related to our rotable parts. As a result, the useful lives of our componentized balance of plant parts are now generally estimated to range from 6 to 25 years and the useful lives of our rotable parts are now generally estimated to range from 1.5 to 12 years. Our change in the estimated useful lives for componentized balance of plant parts and rotable parts is considered a change in accounting estimate and will result in changes to our depreciation expense prospectively. The change in estimate resulted in a (decrease) to our net income attributable to Calpine of $(24) million for the year ended December 31, 2018.

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 8 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 $29 million, $26 million and $21 million for the years ended December 31, 2018, 2017 and 2016, respectively.