John LewisJLBIOSS750

How we test oven heat distribution

We measure how evenly heat is distributed around the oven cavity by baking trays of shortbread on different levels and assessing how evenly they turn out.

How we test accuracy of oven controls

This measures how closely the oven sticks to the temperature we set it at. Some ovens veer a long way from the correct temperature, while others are very accurate.

How we test preheating speed

We measure how quickly the main oven, and the top oven if there is one, heats up to two different set temperatures.

How we test grill

We record which grills spread their heat evenly far and wide, and which ones will have you moving food around to get it evenly browned.

How we test ability to supply heat

We bake a large fatless sponge cake and measure the evenness of browning and how well it rises. This is a measure of how consistently and evenly the oven spreads heat around the cavity.

How we test ease of use

Our assessors check how easy the oven and grill are to use. This includes using the controls, assessing how clear the markings around the buttons and dials are, and the ease of opening and closing the door. They also check how easy it is to adjust shelves and to load and unload food in both the oven and grill.

How we test cleaning

This is the ease of cleaning by hand, and also with any self-clean function.

How we test flexibility of space

We test the flexibility of space inside ovens with joints of beef, chickens and turkeys on roasting trays to see whether the space provided, and the shelf arrangement, allow them to fit in. We then check whether the ovens are flexible enough to allow another roasting tray to be fitted in above. We carry out this test on both top and main ovens.

How we test energy efficiency

We simulate roasting a whole chicken by heating a 2kg brick in the main oven for 1hr 40 mins. Electric conventional ovens are set to 200ºC, electric fan ovens are set to 170ºC and gas ovens at gas mark 6. We measure how much energy the oven uses overall, and also how much energy it uses per litre. Both these recordings feed into the energy efficiency star rating.