Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Public Utilities General Disclosures [Table Text Block]

The Registrants capitalize interest and AFUDC as a component of projects under construction and amortize it over the assets’ estimated useful lives once the assets are placed in service. AFUDC represents the composite interest cost of borrowed funds and a reasonable return on the equity funds used for construction for subsidiaries that apply the guidance for accounting for regulated operations. Although AFUDC increases both utility plant and earnings, it is realized in cash when the assets are included in rates.

	Year Ended December 31,
	2020						2019						2018
	CenterPoint Energy		Houston Electric		CERC		CenterPoint Energy		Houston Electric		CERC		CenterPoint Energy		Houston Electric		CERC
	(in millions)
Interest and AFUDC debt (1)	$	27	$	8	$	3	$	36	$	8	$	3	$	8	$	6	$	2
AFUDC equity (2)	25		14		3		22		15		3		12		10		2

(1)Included in Interest and other finance charges on the Registrants’ respective Statements of Consolidated Income.

(2)Included in Other Income (Expense) on the Registrants’ respective Statements of Consolidated Income.

LIFO Inventory

The Registrants’ inventory consists principally of materials and supplies, and for CERC, natural gas, and for CenterPoint Energy, coal inventory. Materials and supplies are valued at the lower of average cost or market. Materials and supplies are recorded to inventory when purchased and subsequently charged to expense or capitalized to plant when installed. Certain natural gas in storage at CenterPoint Energy’s and CERC’s utilities are recorded using the LIFO method. CenterPoint Energy’s and CERC’s balances in inventory that were valued using LIFO method were as follows:

	Year Ended December 31,
	2020 (1)		2019		2020 (1)		2019
	CenterPoint Energy				CERC
	(in millions)
LIFO inventory	$	92	$	97	$	55	$	58

(1)Based on the average cost of gas purchased during December 2020, CenterPoint Energy’s and CERC’s cost of replacing inventories carried at LIFO cost was less than the carrying value at December 31, 2020 by $62 million and $54 million, respectively.

Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]

The following table provides an overview of certain recently adopted or issued accounting pronouncements applicable to all the Registrants, unless otherwise noted.

Recently Adopted Accounting Standards
ASU Number and Name	Description	Date of Adoption	Financial Statement Impact upon Adoption
ASU 2016-13- Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments	This standard, including standards amending this standard, requires a new model called CECL to estimate credit losses for (1) financial assets subject to credit losses and measured at amortized cost and (2) certain off-balance sheet credit exposures. Upon initial recognition of the exposure, the CECL model requires an entity to estimate the credit losses expected over the life of an exposure based on historical information, current information and reasonable and supportable forecasts, including estimates of prepayments. Transition method: modified retrospective	January 1, 2020	The Registrants adopted the standard and recognized a cumulative-effect adjustment of the transition to opening retained earnings and allowance for credit losses with no impact on results of operations and cash flows. See Note 5 for more information.
ASU 2019-12: Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes	This standard simplifies accounting for income taxes by eliminating certain exceptions to the guidance for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. It also simplifies aspects of the accounting for franchise taxes that are partially based on income and enacted changes in tax laws or rates and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. Transition method: prospective for all amendments that apply to the Registrants	January 1, 2020	Upon adoption, the Registrants are not required to apply the intraperiod tax allocation exception when there is a current-period loss from continuing operations.  Accordingly, CenterPoint Energy determined the tax effect of income from continuing operations without considering the tax effects of items that are not included in continuing operations (i.e., discontinued operations).  Additionally, CenterPoint Energy is no longer required to limit the year-to-date tax benefit recognized when the year-to-date benefit exceeds the anticipated full year benefit.