Editing Mains electricity (section)

=== Standardization ===
Until 1987, mains voltage in large parts of Europe, including Germany, Austria and Switzerland, was {{val|220|22|u=V}} while the UK used {{val|240|14.4|u=V}}. Standard ISO&nbsp;IEC&nbsp;60038:1983 defined the new standard European voltage to be {{val|230|23|u=V}}. From 1987 onwards, a step-wise shift towards {{val|230|+13.8|-23|u=V}} was implemented. From 2009 on, the voltage is permitted to be {{val|230|23|u=V}}.<!-- translation from the German article, see there for additional sources to carry over --><ref>CENELEC Harmonisation Document HD 472 S1:1988</ref><ref>British Standard BS 7697: Nominal voltages for low voltage public electricity supply systems – (Implementation of HD 472 S1)</ref> No change in voltage was required by either the Central European or the UK system, as both 220&nbsp;V and 240&nbsp;V fall within the lower 230&nbsp;V tolerance bands (230&nbsp;V ±6%). Usually the voltage of 230&nbsp;V ±3% is maintained. Some areas of the UK still have 250&nbsp;volts for legacy reasons{{Citation needed|date=January 2025}}, but these also fall within the 10% tolerance band of 230&nbsp;volts. In practice, this allowed countries to have supplied the same voltage (220 or 240&nbsp;V), at least until existing supply transformers are replaced. Equipment (with the exception of [[Incandescent light bulb|filament bulbs]]) used in these countries is designed to accept any voltage within the specified range.

In 2000, [[Australia]] converted to 230&nbsp;V as the nominal standard with a tolerance of +10%/−6%,<ref>{{cite book |author1=Hossain, J. |url=https://books.google.com/books?id=tI_EBAAAQBAJ&q=as60038&pg=PA71 |title=Renewable Energy Integration: Challenges and Solutions |author2=Mahmud, A. |date=29 January 2014 |publisher=Springer |isbn=978-9814585279 |page=71 |access-date=13 January 2018}}</ref> this superseding the old 240&nbsp;V standard, AS&nbsp;2926-1987. The tolerance was increased in 2022 to ±&nbsp;10% with the release of AS&nbsp;IEC&nbsp;60038:2022.<ref>{{Cite web |title=Electrical Contractor Update - Issue 04 - February 2023 |url=https://us5.campaign-archive.com/?u=69932807d57ffb9c816b93a84&id=866a5eb399 |access-date=2024-03-04 |website=us5.campaign-archive.com}}</ref> The utilization voltage available at an appliance may be below this range, due to voltage drops within the customer installation. As in the UK, 240&nbsp;V is within the allowable limits and "240&nbsp;volt" is a synonym for mains in [[Australian English|Australian]] and [[British English]].

In the United States<ref>[[American National Standards Institute|ANSI]]&nbsp;C84.1: [http://www.nema.org/stds/c84-1.cfm American National Standard for Electric Power Systems and Equipment – Voltage Ratings (60 Hertz)] {{webarchive|url=https://web.archive.org/web/20070727234316/http://www.nema.org/stds/c84-1.cfm|date=27 July 2007}}, NEMA (costs $95 for access)</ref><ref name="PG&E_1999">{{cite web |date=1999-01-01 |title=Voltage Tolerance Boundary |url=https://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/voltage_tolerance.pdf |url-status=live |archive-url=https://web.archive.org/web/20191110020717/https://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/voltage_tolerance.pdf |archive-date=2019-11-10 |access-date=2019-11-22 |publisher=PG&E}}</ref> and Canada,<ref>[[CSA Group|CSA]]&nbsp;CAN3-C235-83: Preferred Voltage Levels for AC Systems, 0 to 50,000&nbsp;V</ref> national standards specify that the nominal voltage at the source should be 120&nbsp;V and allow a range of 114&nbsp;V to 126&nbsp;V ([[Root mean square|RMS]]) (−5% to +5%). Historically, 110&nbsp;V, 115&nbsp;V and 117&nbsp;V have been used at different times and places in North America.{{Citation needed|date=November 2022}} Mains power is sometimes spoken of as 110&nbsp;V; however, 120&nbsp;V is the nominal voltage.

In [[Japan]], the electrical power supply to households is at 100 and 200&nbsp;V. Eastern and northern parts of [[Honshu|Honshū]] (including [[Tokyo]]) and [[Hokkaido|Hokkaidō]] have a frequency of 50&nbsp;Hz, whereas western Honshū (including Nagoya, Osaka, and Hiroshima), [[Shikoku]], [[Kyushu|Kyūshū]] and [[Okinawa (city)|Okinawa]] operate at 60&nbsp;Hz. The boundary between the two regions contains four back-to-back [[High-voltage direct current|high-voltage direct-current]] (HVDC) substations which interconnect the power between the two grid systems; these are [[Shin-Shinano Frequency Converter|Shin Shinano]], [[Sakuma Dam#HVDC frequency converter|Sakuma Dam]], [[Minami-Fukumitsu Frequency Converter|Minami-Fukumitsu]], and the [[Higashi-Shimizu Frequency Converter]]. To accommodate the difference, frequency-sensitive appliances marketed in Japan can often be switched between the two frequencies.