INTANGIBLE ASSETS

The following table provides the weighted average amortization rate, gross carrying value, accumulated amortization and net carrying value for each of our major classes of intangible assets:



	Weighted Average			Accumulated
December 31, 2017¹	Amortization Rate		Cost	Amortization	Net
(millions of Canadian dollars)
Customer relationships	3.5	%	967	41	926
Power purchase agreements	3.5	%	99	17	82
Project agreement²	4.0	%	150	3	147
Software	11.3	%	1,760	714	1,046
Other intangible assets³	4.4	%	1,162	96	1,066
			4,138	871	3,267

1 Certain assets were reclassified as held for sale as at December 31, 2017 (Note 7).

2 Represents a project agreement acquired from the Merger Transaction (Note 7).

3 The measurement of weighted average amortization rate excludes non-depreciable intangible assets.



	Weighted Average			Accumulated
December 31, 2016	Amortization Rate		Cost	Amortization	Net
(millions of Canadian dollars)
Customer relationships	3.0	%	251	4	247
Natural gas supply opportunities	3.2	%	435	127	308
Power purchase agreements	3.2	%	100	14	86
Software	11.8	%	1,388	607	781
Other intangible assets	4.8	%	213	62	151
			2,387	814	1,573

For the years ended December 31, 2017, 2016 and 2015, our amortization expense related to intangible assets totaled $280 million, $177 million and $158 million, respectively. The following table presents our forecast of amortization expense associated with existing intangible assets for the years indicated as follows in millions of Canadian dollars:



2018	2019	2020	2021	2022
264	240	217	197	179