Use the most efficient appliance for the job. The holidays can mean more time in the kitchen whipping up meals and treats. A slow cooker is more energy efficient than a stovetop for stews and soups, while a toaster oven uses a fraction of the electricity of an oven if you need to reheat a slice of pizza. And when baking, do not peek into the oven, Rubado says. Every time you open the door, the oven temperature drops about 25 degrees, she says, and it has to work harder to climb back to its set temperature. But when you’re done using the oven and turn it off, Ciavardini says, leave the door open, so the residual heat can help warm the kitchen.