The AGA cooker is a heat storage stove and cooker, which works on the principle that a heavy frame made from cast iron components can absorb heat from a relatively low-intensity but continuously-burning source, and the accumulated heat can then be used when needed for cooking. Originally heated by slow-burning coal, the Aga cooker was invented in 1922 by the Nobel Prize-winning Swedish physicist Gustaf Dalén (1869–1937), who was employed first as the chief engineer of the Swedish AGA company (Swedish: Aktiebolaget Svenska Gasaccumulator, English: Joint stock company Swedish Gas Accumulator). The cookers were first imported to Britain in 1929, and were first manufactured there under licence in the early 1930s. The cast iron components were first cast at the Coalbrookdale foundry in the 1940s, where they are still made today by the Aga Rangemaster Group.
Gustaf Dalen lost his sight in an explosion while developing his earlier invention, a porous substrate for storing gases, Agamassan. Forced to stay at home, Dalen discovered that his wife was exhausted by cooking. Although blind, he set out to develop a new stove that was capable of a range of culinary techniques and easy to use.
Adopting the principle of heat storage, he combined a heat source, two large hotplates and two ovens into one unit: the AGA Cooker. The cooker was introduced to England in 1929, and its popularity in certain parts of English society (owners of medium to large country houses) led to the coining of the term "AGA Saga" in the 1990s, referring to a genre of fiction set amongst stereotypical upper-middle-class society.
Aga cookers can also make a contribution to space heating, although it is not true that they can heat an entire house, despite persistent claims to the contrary, presumably arising because the cookers look similar to the many types of central-heating range such as the 'Stanley' or the 'Rayburn' Range, also made by the AGA Rangemaster Group.
AGA has provided an analysis of their own, which includes the steps taken to reduce energy consumption.
Owners often talk about how the AGA actually makes their homes more energy efficient, as the AGA does a number of jobs, such as replacing several radiators, and is not simply a cooker. They also use the fact that it is made from recycled materials and claimed to last for at least half a century to back this up.
The vast majority of AGAs sold today are programmable and AGA announced an upgrade initiative in 2009, meaning that owners of older AGA cookers can have them modified so they are programmable. The latest model the AGA Total Control  uses the same radiant heat to cook (without drying the food out), but is designed to be switched off like a regular cooker when not in use, using far less energy as a result.
Three main models of AGA are currently in production: two-, three- and four-oven versions, with the four-oven version wider than the others. The two-oven model has three doors behind which are the burner, roasting oven and simmering oven. The newer three-oven model also includes a baking oven, and the four-oven version also has a warming oven and warming plate on the top. All models have two hotplates — a boiling plate and a simmering plate. The cookers come in a range of different colours, but the most popular is the original cream and, more recently, aqua.
Fuel options include kerosene, diesel, biofuel, gas or electricity. Electrical models,some of which can be controlled by a smartphone, make up nearly three-quarters of all sales, while just one in twenty customers are after a conventional oil-powered Aga. AGA Dual Control model has three or five electric ovens on one system and two separate hobs. It has proved popular with owners used to keeping a classic AGA on for sustained periods but who want to cut the running costs.
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A new model AGA - AGA City60, was launched in July 2014. At just 60cm wide – the same size as a slot-in cooker or a standard kitchen unit – it’s perfect for compact spaces. Just like other iconic AGA cookers, it's made from cast iron and employs radiant heat cooking technology. There are two ovens, offering roasting, baking and simmering functions and a hotplate, which enables boiling and simmering. Plus, the main oven, which can be set to either baking or roasting, can be fully programmable and can have up to three events pre-set per day. In the winter one can enjoy the indefinable AGA warmth in the kitchen and in the summer the AGA City60 can be switched on or off.
The AGA is known for its longevity, with many cookers still operating after more than 50 years. In 2009, in conjunction with the Daily Telegraph and to celebrate the 80th anniversary of its founding, AGA set up a competition to find the oldest AGA still in use. There were thousands of entries, but the winning cooker was installed in 1932 and belonged to the Hett family from Sussex. This cooker is now installed in the reception area of the company's Coalbrookdale foundry.
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- Edwards, Adam (2008-11-01). "AGA cooker: Hot on the trail of our oldest AGA". The Daily Telegraph (London). Retrieved 2010-04-23.
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