Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment and Estimated Useful Lives of Property, Plant and Equipment

Property, Plant and Equipment
As of December 31	2023	2022
Millions
Regulated Operations
Property, Plant and Equipment in Service	$5,167.2	$5,198.6
Construction Work in Progress	146.7	74.0
Accumulated Depreciation	(1,969.4)	(1,972.3)
Regulated Operations – Net	3,344.5	3,300.3
ALLETE Clean Energy
Property, Plant and Equipment in Service	1,612.8	1,619.4
Construction Work in Progress	48.9	51.1
Accumulated Depreciation	(229.1)	(176.8)
ALLETE Clean Energy – Net	1,432.6	1,493.7
Corporate and Other (a)
Property, Plant and Equipment in Service	355.8	295.2
Construction Work in Progress	27.5	50.9
Accumulated Depreciation	(147.0)	(136.1)
Corporate and Other – Net	236.3	210.0
Property, Plant and Equipment – Net	$5,013.4	$5,004.0

(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	4 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

Asset Retirement Obligations
Millions
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
Accretion	10.3
Liabilities Settled	(10.2)
Revisions in Estimated Cash Flows	2.4
Obligation as of December 31, 2023	$202.9