One example is bread. I was baking bread the other day, and obviously the cost of the ingredients I put in the loaf are less than the cost of buying a loaf at the supermarket, but that doesn’t include the cost of putting the oven on.
Or dry beans vs canned beans; does the cost of boiling the beans actually bring the cost up to be equivalent to canned beans?
I know that everyone’s energy costs are different so it’s not possible for someone to do the calculations for you, but I’ve never bothered to do them for my own case because bills I get from the energy company just tell me how much I owe them for the month, not “you put the oven on for 30 minutes on the 17th of June and that cost you X”. It sounds like a headache to try calculate how much I pay for energy per meal. But if someone else has done that calculation for themselves I’d be interested to read it and see how it works out. My intuition is that, in general, it’s cheaper to make things yourself (e.g. bread or beans like above), but I couldn’t say that for sure without calculating, which as I said seems like it would be a pain in the ass.
I don’t have a calculation to back it up, but I’m inclined to believe store bought will always have a cheaper production cost. Your can of beans wasn’t made by one person per one can of beans at a time. It is done in a factory producing millions of cans. That kind of industrial process will always be cheaper. It’s designed to be that way. Beans can be bought wholesale below the cost available to you. And with that operation at scale it will undoubtedly be more energy efficient per can of beans. The consumer cost is something else. You will save money buying the raw ingredients and making your own beans rather than buying canned.
I did the math a little bit ago because I was baking a lot of bread, and I think depending on the bread it was actually cheaper to buy the same kind of loaf baked in my grocery store than to buy the equivalent ingredients. This was a Publix though which at least in my area are on the more expensive end and they didn’t have store brand bread flour so I had to go with a fancy brand.