Use a toaster oven or my big oven?
I often bake a tray of brownies with my grandchild. I use the big oven, which is new and pretty efficient, can not feel any heat coming off of it at all.
I was wondering about toaster ovens, years ago they used more energy, but I wonder if the newer ones would be more efficient for small items such as brownies, frozen pizzas etc.
If so , which is a good one to purchase?
The energy efficiency of a resistance-based heating element (which is probably what is in both your stove oven and in whatever toaster oven you buy) is always virtually 100%. This means 100% of the electricity coming out of the stove or toaster oven plug is converted into heat.
For a regular electric oven, you are probably looking at about 6 cubic feet of air space. For a large toaster oven you are probably looking at about 0.75 cubic feet. So it will take a lot less energy to preheat a toaster oven – about one eighth as much if you assume both are very well insulated.
Regular ovens, however, are much better insulated than most toaster ovens; self cleaning ovens even more so. This means that quite a bit of the heat required for both preheating and baking will escape through the toaster oven walls. So the longer you are going to bake without opening the oven, the more efficient it will be compared to the toaster oven.
If you are baking just one batch of something that takes 12 minutes (like cookies), a toaster oven may be more efficient. But if you're baking several batches of cookies, or a dish that takes 45 minutes or longer, a regular oven is definitely better. And you can do even better by ensuring you bake several things together in the main oven.
Another thing to consider is that toaster ovens usually don't have nearly as precise a temperature control as stove ovens, so you're more likely to have raw or burnt brownies.
Finally, have you considered a microwave convection oven instead of a toaster oven? While these are more expensive than toaster ovens or even conventional ovens, they are great for baking, roasting, and microwaving. We have one at home and use it to bake cookies, pies, savory dishes, as well as warm that cold cup of coffee and roast chicken thighs. It uses a combination of convection heat (more efficient for baking than the conduction heat of a regular or toaster oven) and microwave heat to do baking or roasting with less energy.