An electric steam boiler is a type of boiler

Boiler

A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.-Materials:...

 where the steam

Steam

Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

 is generated using electricity, rather than through the combustion of a fuel source. They are used to generate steam for process purposes in many locations, for example laundries

Industrial laundry

Large institutions that require a constant flow of clean linen, working-clothing or uniform, will often employ the services of an industrial laundry. Hospitals, prisons and hotels, for instance, will usually have their own laundry departments. The organized collection, laundering and timely...

, food processing

Food processing

Food processing is the set of methods and techniques used to transform raw ingredients into food or to transform food into other forms for consumption by humans or animals either in the home or by the food processing industry...

 factories and hospital

Hospital

A hospital is a health care institution providing patient treatment by specialized staff and equipment. Hospitals often, but not always, provide for inpatient care or longer-term patient stays....

s. Although they are more expensive to run than gas-fired or oil-fired boilers they are popular because of their simplicity and ease of use. Because of the large currents required, they are normally run from a three-phase

Three-phase

In electrical engineering, three-phase electric power systems have at least three conductors carrying voltage waveforms that are radians offset in time...

 electricity supply

Electricity distribution

File:Electricity grid simple- North America.svg|thumb|380px|right|Simplified diagram of AC electricity distribution from generation stations to consumers...

. They convert electrical energy into thermal energy

Thermal energy

Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system's temperature....

 with almost 100% efficiency but the overall thermal efficiency

Thermal efficiency

In thermodynamics, the thermal efficiency is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, a boiler, a furnace, or a refrigerator for example.-Overview:...

is variable, depending on the efficiency with which the electricity is generated.