Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2022

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment and Estimated Useful Lives of Property, Plant and Equipment [Table Text Block]

Property, Plant and Equipment
As of December 31	2022	2021
Millions
Regulated Operations
Property, Plant and Equipment in Service	$5,198.6	$5,028.7
Construction Work in Progress	74.0	108.7
Accumulated Depreciation	(1,972.3)	(1,834.6)
Regulated Operations – Net	3,300.3	3,302.8
ALLETE Clean Energy
Property, Plant and Equipment in Service	1,619.4	1,704.2
Construction Work in Progress	51.1	79.9
Accumulated Depreciation	(176.8)	(149.0)
ALLETE Clean Energy – Net	1,493.7	1,635.1
Corporate and Other (a)
Property, Plant and Equipment in Service	295.2	267.1
Construction Work in Progress	50.9	19.8
Accumulated Depreciation	(136.1)	(137.3)
Corporate and Other – Net	210.0	149.6
Property, Plant and Equipment – Net	$5,004.0	$5,087.5

(a)Primarily includes BNI Energy and a small amount of non-rate base generation.

Estimated Useful Lives of Property, Plant and Equipment (Years)
Regulated Operations
Generation	1 to 50	ALLETE Clean Energy	5 to 35
Transmission	50 to 75	Corporate and Other	3 to 50
Distribution	18 to 70

Asset Retirement Obligations [Table Text Block]

Asset Retirement Obligations
Millions
Obligation as of December 31, 2020	$166.6
Accretion	8.8
Liabilities Recognized	4.5
Liabilities Settled	(5.2)
Revisions in Estimated Cash Flows	9.8
Obligation as of December 31, 2021	184.5
Accretion	9.5
Liabilities Recognized	7.8
Liabilities Settled	(4.4)
Revisions in Estimated Cash Flows	3.0
Obligation as of December 31, 2022	$200.4