Mains is the general-purpose alternating-current (AC) electric power supply. In the US, electric power is referred to by several names including household power, household electricity, house current, powerline, domestic power, wall power, line power, AC power, city power, street power, and grid power. In many parts of Canada, it is called hydro, because much of the Canadian electrical generating capacity is hydroelectric.

For a list of voltages, frequencies, and wall plugs by country, see Mains electricity by country

Worldwide, many different mains power systems are found for the operation of household and light commercial electrical appliances and lighting. The different systems are primarily characterized by their

All these parameters vary among regions. The voltages are generally in the range 100–240 V (always expressed as root-mean-square voltage). The two commonly used frequencies are 50 Hz and 60 Hz.

Foreign enclaves, such as large industrial plants or overseas military bases, may have a different standard voltage and frequency from the surrounding areas. Some city areas may use standards different from that of the surrounding countryside (e.g. in Libya). Regions in an effective state of anarchy may have no central electrical authority, with electric power provided by incompatible private sources.

The Grid are an English electronic dance group, consisting of Richard Norris and David Ball (formerly of Soft Cell), with guest contributions from other musicians. They are best known for the hits "Swamp Thing", "Crystal Clear", "Rollercoaster", "Floatation", and "Cybernetic" (with Robert Fripp and Phil Manzanera).

The Grid formed in 1988 and had their first success with debut single, "Floatation", released on East West Records in 1990. They went on to release a string of ten UK hit singles and four albums, and toured the UK, Europe, Asia and Australia. The group's 1994 album Evolver reached #14 in the UK Albums Chart. The lead single from this album, "Swamp Thing", featuring elaborate banjo lines played by Roger Dinsdale. "Swamp Thing" proved to be a commercial success in the UK, Europe and Australia, reaching #3 in the UK and Australia and selling a total of one million copies.^{[citation needed]}

In 1996, Norris and Ball agreed to a hiatus period in order pursue individual music interests. Norris formed the Droyds, which went on to remix tracks by musicians including Armand Van Helden and Siobhan Fahey, and wrote the official biography of Paul Oakenfold (published in 2007): Ball reformed Soft Cell with Marc Almond, and also wrote music scores for films.^{[citation needed]} Norris has since formed the psychedelic duo, Beyond The Wizard's Sleeve, with DJ Erol Alkan, and has released a number of solo records and remixes under the name The Time and Space Machine.