I often have a bad habit of constantly opening the door of the oven to check the doneness! Very bad for savings energy because the heat loss is very important
As soon as the oven door is open, the oven loses several degrees! And it's even worse during warm-up.
So try to keep the oven door closed as much as possible. You will still have to open it to take the dish out, but that's it!;-)
If your oven has interior lighting, now is the time to use it to check for doneness. You still have to clean the glass to see anything...
Save energy it is on a daily basis that this is worked for all the clever stingy people! Leave the door of the oven maximally closed while cooking is one of those little things that saves money on your bill.
If, like me, you are used to opening constantly, you will quickly see the difference in consumption on your bills, especially if you have an oven electric that consumes more than a gas oven.