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’m a cook as a hobby, so typically the cost of making vs buying does not figure into my decision, except when things at the store get absurdly expensive.
A case in point: Toasted Sliced Salted Salad Almonds from Fresh Gourmet
My wife and I love these on our dinner salads so we go through a lot of them. The cost of a package of these salad almonds has risen to $7 for a 3.5oz (99g)package.
I can buy a 16oz (454g) package of raw almonds for almost the same amount of money, as the 3.5oz (99g) Fresh Gourmet package. I have an electric oven that consumes around 5kwh that runs for roughly 30 minutes during preparation and my daytime electric rate is around $0.13/kwh (I think).
Out of that I get a full pound (16oz, 454g) of salted almonds for ~$7.07 and 30 minutes of my time. I also use about $0.02 worth of salt, bringing the total cost to ~$7.09 for 4.5 times more almonds.
I also can adjust the amount of salt on them as well, as typically my wife and I like less salt that most people.
It’s also fun to do.