Mains electricity
Mains electricity, utility power, grid power, domestic power, wall power, household current, or, in some parts of Canada, hydro, is a general-purpose alternating-current electric power supply. It is the form of electrical power that is delivered to homes and businesses through the electrical grid in many parts of the world. People use this electricity to power everyday items by plugging them into a wall outlet.
The voltage and frequency of electric power differs between regions. In much of the world, a voltage of 230 volts and frequency of 50 Hz is used. In North America, the most common combination is 120 V and a frequency of 60 Hz. Other combinations exist, for example, 230 V at 60 Hz. Travellers' portable appliances may be inoperative or damaged by foreign electrical supplies. Non-interchangeable plugs and sockets in different regions provide some protection from accidental use of appliances with incompatible voltage and frequency requirements.
Terminology
In the US, the electricity that a building receives is called an electrical service, and what comes out of a receptacle is referred to by its voltage, such as 120 or 240. Sometimes it might be referred to by its number of phases, such as Three Phase.In the UK, mains electric power is generally referred to as "the mains".
More than half of power in Canada is hydroelectricity, and mains electricity is often referred to as "hydro" in some regions of the country. This is also reflected in names of current and historical electricity utilities such as Hydro-Québec, BC Hydro, Manitoba Hydro, Hydro One, and Newfoundland and Labrador Hydro.
Power systems
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:- Voltage
- Frequency
- Plugs and sockets
- Earthing system
- Protection against overcurrent damage, electric shock, and fire hazards
- Parameter tolerances.
Many other combinations of voltage and utility frequency were formerly used, with frequencies between 25 Hz and 133 Hz and voltages from 100 V to 250 V. Direct current has been displaced by alternating current in public power systems, but DC was used especially in some city areas to the end of the 20th century. The modern combinations of 230 V/50 Hz and 120 V/60 Hz, listed in IEC 60038, did not apply in the first few decades of the 20th century and are still not universal. Industrial plants with three-phase power will have different, higher voltages installed for large equipment, but the common voltages listed here would still be found for lighting and portable equipment.
Common uses of electricity
Electricity is used for lighting, heating, cooling, electric motors and electronic equipment. The US Energy Information Administration has published:U.S. residential sector electricity consumption by major end uses in 2021
| End use | Petajoules | Share of total |
| Space cooling | 15% | |
| Space heating | 14% | |
| Water heating | 12% | |
| Refrigeration | 6% | |
| Clothes dryers | 4% | |
| Lighting | 4% | |
| Televisions and related equipment1 | 4% | |
| Computers and related equipment2 | 2% | |
| Furnace fans and boiler circulation pumps | 2% | |
| Freezers | 1% | |
| Cooking | 1% | |
| Clothes washers3 | 1% | |
| Dishwashers3 | 1% | |
| Other uses4 | 34% | |
| Total consumption | 100% |
Electronic appliances such as computers or televisions sets typically use an AC to DC converter or AC adapter to power the device. This is often capable of operation with a wide range of voltage and with both common power frequencies. Other AC applications usually have much more restricted input ranges.
Building wiring
| Standard | Earth/Ground wire | Neutral wire | Live/Phase 1 wire | Live/Phase 2 wire | Live/Phase 3 wire |
| UK & Europe | green/yellow | blue | brown | black | gray |
| UK | green/yellow | black | red | yellow | blue |
| United States | green | white | black | red | blue |
| Australia | green/yellow | black | red | white | blue |
Portable appliances use single-phase electric power, with two or three wired contacts at each outlet. Two wires carry current to operate the device. A third wire, not always present, connects conductive parts of the appliance case to earth ground. This protects users from electric shock if live internal parts accidentally contact the case.
In northern and central Europe, residential electrical supply is commonly 400 V three-phase electric power, which gives 230 V between any single phase and neutral; house wiring may be a mix of three-phase and single-phase circuits, but three-phase residential use is rare in the UK. High-power appliances such as kitchen stoves, water heaters and household power heavy tools like log splitters may be supplied from the 400 V three-phase power supply.
Small portable electrical equipment is connected to the power supply through flexible cables terminated in a plug, which is inserted into a fixed receptacle. Larger household electrical equipment and industrial equipment may be permanently wired to the fixed wiring of the building. For example, in North American homes a window-mounted self-contained air conditioner unit would be connected to a wall plug, whereas the central air conditioning for a whole home would be permanently wired. Larger plug and socket combinations are used for industrial equipment carrying larger currents, higher voltages, or three phase electric power.
Safety systems
s and fuses are used to detect short circuits between the line and neutral or ground wires or the drawing of more current than the wires are rated to handle to prevent overheating and possible fire. These protective devices are usually mounted in a central panel—most commonly a distribution board or consumer unit—in a building, but some wiring systems also provide a protection device at the socket or within the plug. Residual-current devices, also known as ground-fault circuit interrupters and appliance leakage current interrupters, are used to detect ground faults—flow of current in other than the neutral and line wires. When a ground fault is detected, the device quickly cuts off the circuit.The terms "ground wires" and "earth wires" are used interchangeably, depending on regional differences, for a wire that connects to the earth or some conducting body that serves in place of the earth to take the electrical discharge. Grounding wires are installed as a safety feature in order to route electricity into another safe body that is not electrically conductive like the air or ground in order to prevent short circuits or electrocution.
Voltage levels
Most of the world population use a supply that is within 6% of 230 V. In the United Kingdom the nominal supply voltage is 230 V +10%/−6% to accommodate the fact that most transformers are in fact still set to 240 V. The 230 V standard has become widespread so that 230 V equipment can be used in most parts of the world with the aid of an adapter or a change to the equipment's plug to the standard for the specific country.The United States and Canada use a supply voltage of 120 volts ± 6%. Japan, Taiwan, Saudi Arabia, North America, Central America and some parts of northern South America use a voltage between 100 V and 127 V. However, most of the households in Japan equip split-phase electric power like the United States, which can supply 200 V by using reversed phase at the same time. Brazil is unusual in having both 127 V and 220 V systems at 60 Hz and also permitting interchangeable plugs and sockets. Saudi Arabia and Mexico have mixed voltage systems; in residential and light commercial buildings both countries use 127 volts, with 220 volts at 60 Hz in commercial and industrial applications. The Saudi government approved plans in August 2010 to transition the country to a totally 230/400-volt 60 Hz system.