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’ve been making bread regularly for years. A 1-lb loaf costs me about 90 cents USD for ingredients and 15 cents to run the oven. “Nice” Safeway bakery loaves that roughly correspond to what I make cost anywhere from $3-$6, and the whole process takes me 10-15 minutes of actual effort (including cleanup). I don’t count rising and baking times because I’m doing other stuff.
Having also consumed a lot of packaged food (I’m not a crusader against it) I would say cooking meals from store-bought ingredients costs around half as much. Home-growing vegetables adds a huge amount more work. I did a garden for 2 years, many years ago - it was more of a fun project. On the scale I did it I never felt the hours of labor paid off dollar-wise. And what with mulch and other things gardening is something you can pretty much spend as much money on as you want lol.
Fun fact: if you go to the deli counter and get them to slice meat for you it’s about half the price of the store-brand deli packs on the shelves, which are the exact same meats, sliced and packaged by the same people. The only difference is you stand there waiting for a minute while they do it instead just grabbing it off the shelf. The high price of even marginal convenience.
How? Flour here is up to about $7 for a 5lb bag (2.2kg) and I make 2 loaves with 1kg flour, I’m at $1.50 per loaf flour only, not counting the flour that went into the starter, or electricity or time, or other ingredients (brioche uses eggs & milk, pan de mie lots of butter, sandwich bread I usually use whole wheat and some oats and milk, a little butter or olive oil, focaccia lots of olive oil, stuff like that) . I don’t even use packaged yeast and figure my cost is likely $3-4 per loaf.
Flour I buy from Costco costs 90 cents/lb, salt and yeast for one loaf are less than a nickel, and gas to run the oven (including preheat time) is like 15 cents where I live. So maybe $1.15-1.20 per loaf. I’m talking about the basic loaf of bread I make all the time. Brioche etc. will be more, and you can get as fancy as you want, but those items correspondingly cost more from a bakery too. Doing a little of the actual math, eggs are abnormally expensive right now but say $1 each, a cup and a half of milk from Safeway would add another $.65, so call it $2.80 per loaf for fancy bread that would cost 2x-3x that much already made.