A block heater warms an engine

Engine

An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...

 to ease and speed starting and vehicle warmup in cold weather. The most common type is an electric heating

Electric heating

Electric heating is any process in which electrical energy is converted to heat. Common applications include space heating, cooking, water heating and industrial processes. An electric heater is an electrical appliance that converts electrical energy into heat...

 element connected through a power cord

Power cord

A power cord, line cord, or mains cable is a cable that temporarily connects an appliance to the mains electricity supply via a wall socket or extension cord. The terms are generally used for cables using a power plug to connect to a single-phase alternating current power source at the local line...

 often routed through the vehicle's grille

Grille

A grille or grill is an opening of several slits side by side in a wall or metal sheet or other barrier, usually to let air or water enter and/or leave but keep larger objects including people and animals in or out.-Spelling:In the United States, "grille" is used to differentiate the automotive...

. The block heater may replace one of the engine's core plug

Core plug

Core plugs, sometimes wrongly called freeze plugs or frost plugs, are plugs that fill the core holes found on water-cooled internal combustion engines....

s, or may be installed in line with one of the radiator or heater hoses. Block heaters that run on the vehicle's own gasoline

Gasoline

Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...

 or diesel fuel supply are also available; these require no external power source. The coolant

Antifreeze

Antifreeze is a freeze preventive used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters....

 is heated and circulated, usually by thermosiphon

Thermosiphon

Thermosiphon refers to a method of passive heat exchange based on natural convection which circulates liquid without the necessity of a mechanical pump...

, through the engine and the vehicle's heater core

Heater Core

A heater core is a radiator-like device used in heating the cabin of a vehicle. Hot coolant from the vehicle's engine is passed through a winding tube of the core, a heat exchanger between coolant and cabin air...

. Heaters are also available for engine oil

Motor oil

Motor oil or engine oil is an oil used for lubrication of various internal combustion engines. The main function is to lubricate moving parts; it also cleans, inhibits corrosion, improves sealing, and cools the engine by carrying heat away from moving parts.Motor oils are derived from...

 so that warm oil can quickly circulate throughout the engine during startup. The easier starting results from warmer, less viscous engine oil and less condensation

Condensation

Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....

 of fuel on cold metal surfaces inside the engine; thus a block heater reduces a vehicle's emission of unburned hydrocarbons and carbon monoxide; also heat is available more quickly for the passenger compartment and glass defogging

Defogger

A defogger, demister, or defroster is a system to clear condensation and thaw frost from the windshield, backglass, and/or side windows of a motor vehicle...

.

Block heaters or coolant heaters are also found on permanently installed systems using diesel engines to allow standby generator

Standby generator

thumb|right|Standby generatorsA standby generator is a back-up electrical system that operates automatically. Within seconds of a utility outage an automatic transfer switch senses the power loss, commands the generator to start and then transfers the electrical load to the generator. The standby...

 sets to take up load quickly in an emergency.

Usage

Block heaters are widely used in regions with cold winters such as the northern U.S., and parts of Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 and Scandinavia

Scandinavia

Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...

. In colder climates, block heaters are often standard equipment in new vehicles. In extremely cold climates, electrical outlets are sometimes found in public or private parking lots, especially in multi-storey car park

Multi-storey car park

A multi-storey car-park is a building designed specifically to be for car parking and where there are a number of floors or levels on which parking takes place...

s. Some parking lots cycle the power on for 20 minutes and off for 20 minutes, in order to reduce electricity costs.

Research by the Agricultural Engineering

Agricultural engineering

Agricultural engineering is the engineering discipline that applies engineering science and technology to agricultural production and processing...

 Department of the University of Saskatchewan

University of Saskatchewan

The University of Saskatchewan is a Canadian public research university, founded in 1907, and located on the east side of the South Saskatchewan River in Saskatoon, Saskatchewan, Canada. An "Act to establish and incorporate a University for the Province of Saskatchewan" was passed by the...

 has shown that operating a block heater for longer than four hours prior to starting a vehicle is a waste of energy. It was found that coolant

Antifreeze

Antifreeze is a freeze preventive used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters....

 temperature increased by almost 20 C-change degrees in that period, regardless of the initial temperature (4 tests were run at ambient temperatures ranging from -11 C to -29 C); continued use of the heater for a further one or two, or more, hours achieved a mere 2 or 3 more degrees Celsius as conditions stabilized. Engine oil temperature was found to increase over these periods by just 5 C-change.

There are alternatives to a block heater that offer some of the same benefits. These include heaters attached to the engine's oil pan, usually with magnets. Dipstick

Dipstick

A dipstick is one of several measurement devices.Some dipsticks are dipped into a liquid to perform a chemical test or to provide a measure of quantity of the liquid....

 heaters can be installed in place of the engine's oil dipstick. Heated blankets are available for the entire engine area, as well. A timer

Timer

A timer is a specialized type of clock. A timer can be used to control the sequence of an event or process. Whereas a stopwatch counts upwards from zero for measuring elapsed time, a timer counts down from a specified time interval, like an hourglass.Timers can be mechanical, electromechanical,...

 can be used with any of these heaters, so that it does not have to be left on all the time. This can help lower the electrical costs of using a block heater.

Some cars, such as the second generation Toyota Prius

Toyota Prius

The Toyota Prius is a full hybrid electric mid-size hatchback, formerly a compact sedan developed and manufactured by the Toyota Motor Corporation...

, pump hot coolant from the cooling system into a 3 litre insulated thermos

Thermos

Thermos may refer to:* A vacuum flask generically known as a "thermos"* a brand of domestic vacuum flask made by Thermos L.L.C.* Thermos , an ancient Greek city, the capital city of the Aetolian League...

-style reservoir at shutdown, where it stays warm for up to 3 days.

History

Andrew Freeman

Andrew Freeman

Andrew Freeman , was the inventor of the electric block heater for automobiles.Freeman first developed a block heater around 1940, and received U.S. Patent #2487326 on 8 November 1949....

 of Grand Forks, North Dakota invented the head bolt heater in around 1940 and received a patent for it on November 8, 1949. In 1951, Freeman received another patent on an improved head bolt heater. These early heaters replaced one of the engine's cylinder head

Cylinder head

In an internal combustion engine, the cylinder head sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket...

 bolt

Bolt

-Fasteners:*A cap screw, as used in a bolted joint*Screw, a cylindrical threaded fastener*Dead bolt, a kind of locking mechanism*Bolt , an anchor point used in rock climbing-Weaponry:*Bolt , a mechanism used in firearms...

s with a hollow, threaded shank containing a resistive heating element. Before the block heater was invented, people utilized various means of warming engines before starting them, such as pouring hot water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 on the engine block or draining the engine's oil for storage inside overnight. Some even shoveled hot coals underneath their vehicle's engine to achieve the same effect.

During the dawn of aviation in pre-war Northern Canada, aviators flew with flight engineers who were responsible for preparing the radial engine

Radial engine

The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...

s for shutdown and startup in order to mitigate the effects of sub-zero temperatures. The flight engineer was responsible for draining the oil into buckets at night, and pre-heating both the engine and the buckets of oil using a blanket wrapped around the engine and a device known as a blow pot, essentially, a kerosene

Kerosene

Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...

jet-heater used several hours prior to flight.