Fan and fan-assisted ovens
In conventional ovens, and particularly in gas ovens, the area in the top of the oven is hotter than the area in the bottom (a phenomenon known as 'zoned heat difference'). This can be useful if you are cooking several items at once, but want one to cook faster than the others.
Fan ovens
With fan (or 'convection') ovens, the heat is pushed around by an electric fan – usually located in the back wall of the oven – so the entire cavity is filled with consistent heat. The circulation of hot air within the oven lends a welcome dry-heat effect to some foods: meat or fish, for example, laid on a wire rack, cook in a way that begins to resemble cooking on an open fire or on a barbecue, with a crisp exterior. Another advantage of fan ovens is that – compared to conventional ovens – they take far less time to heat up.
Most fan ovens are electric ovens, but some gas ovens are fitted with fans.
Fan-assisted ovens
There is in fact a distinction between a fan oven and a fan-assisted oven. Fan ovens have an electric heating element in front of the fan. Fan-assisted ovens have conventional heating elements in the top and bottom of the oven; the fan has the task of simply pushing the heated air around. But in terms of usage, there is little difference, except that a fan-assisted oven takes slightly longer to warm up.
Turning down the heat
Note also that, because of the more efficient way that the fans transfer heat, cooking times and/or temperatures need to be reduced, typically by 10 per cent for anything that stays in the oven for longer than 25 minutes.
