Your oven is a great cooking tool and roasted meals are typically easy and delicious.
The average full-size oven has 30 pounds of steel and so heating all that mass is no small energy feat. A great energy-efficiency trick is to use it for several meals once it's hot, including tomorrow's breakfast or lunch or maybe precook dinner for a busy evening you see later this week. You'll save energy AND your future self will thank you for an easy warm-and-enjoy meal. Warming food in the microwave takes much less energy than cooking it from scratch in the oven. Can't get any more "fast food" than that!
There's so much volume in there and more food does not significantly add to the amount of energy required to keep the oven at a constant temperature. The main glug of energy occurs when you bring the oven from room temperature to roasting temperature. Once you're there - have at it!!
So, next time you heat up your oven, think of other uses for this cooking potential.....
* Bake up a batch of granola for breakfast! (recipe coming soon)
* Roast some peppers for a yummy sandwich for lunch tomorrow.
* Roast some tomatoes for a quick pasta sauce (starting with fresh tomatoes and making this quick pasta topping saves a single-use jar, since you don't have to buy tomato sauce at the store now!).
* Whip up a quick loaf of 1-hour bread (recipe coming soon).
* Roast tonight's veggies rather than using the energy to bring a pot of water to boil to cook them on the stove.
The possibilities are endless and if it results in turning on your oven half as often - that's a great energy reduction!
Note that this is not such a great help in the winter when we are using energy to heat our homes anyway. BUT. - bonus points using this strategy in the summer. If your home has air conditioning, firing up your oven not only uses the energy to heat the oven and food but also requires your air conditioner to work harder (more energy) to cool off the house!