I love to waste some time with a good optimization challenge. My go-to for this experience is Factorio, but sometimes I enjoy micro-optimizing things in real life too! We've just got a new bread maker, the Panasonic SD-B2510, and are making extensive use of it, running it about once every 2 days, so I thought I'd work how how much it's costing us to see if it's saving us against shop-bought loaves.
We'd continue to use it even if it's a bit more expensive, because it delivers fresh, tasty, and non-UPF bread with very little effort, and it's much easier to carry bags of flour back from the supermarket than it is to carry loaves.
The standard loaf we make is with setting 1, 'medium' size with a 'dark' crust. Because we want a zero-fat loaf, we don't use the recipe in the booklet but instead use 400g strong flour, 1 sachet (~7g) easy bake yeast, 1 tsp salt, and 290ml water. This this cooks for 4 hours. I'm going to say the water is free - we pay about 250p per cubic metre, so this about 0.1p of water. 1tsp of salt is also nearly free, I'm going to assume it's 1p.
There are 3 major components to the cost then: flour, yeast, and electricity. Our local shop is a Tesco, so I'm going to use prices from there.To measure electricity, I plugged the machine into one of there digital power meters and checked - 423Wh for a run, which at my tariff is about 15p.
So baseline cost for a 700g (400g flour + 290g water + yeast) loaf from the machine is 74p. If instead we used loose yeast, then it would be 62p, and on the occasion we can run it in one of the half-price electricity windows that our provider runs it would be 54p. I'm going to take 62p as the final cost, since we can easily adjust to use loose yeast but can't guarantee the half-price power.
Potentially we could also use plain flour rather than strong flour, which is much cheaper—78p for 1.5kg, which is 21p per loaf. This would take the cost down to 48p per loaf, at the cost of having a less springy bread.
For a couple of price points, a Hovis 800g loaf is 139p, and an own-brand 800g loaf goes for 74p. Scaling those down to 700g is 122p and 65p.
Compared to own-brand, the bread machine saves 4p a loaf. That's 3.75k loaves to recoup the cost of the machine.
250 loaves seems plausible, we might manage that in a year and I hope the machine won't break down by then. PerplexityAI thinks that I should expect 400-1k loaves before needing some sort of maintenance. But against own-brand; no, I don't think I'm going to be able to recoup the machine cost before it needs maintenance. The maintenance probably won't be as expensive as a brand new machine, but I'm assuming worst case.
Consider also, having ~infinite bread at home might displace other non-bread options for food? Those might have been significantly more expensive that the comparison loaves.
I think for practical purposes if you like bread then it's worth getting one of these machines. You'll get nicer bread for only 5 minutes of effort a loaf, and that bread will probably be cheaper than the bread you'd buy otherwise. You can also add herbs to the machine freely to get a greater variety.
If you only care about cost reduction and treat bread as a pleasureless commodity, then you might get lucky and save a bit, particularly if you go for plain flour, or have half-price electricity windows, or the machine holds out for longer before breaking down. But if you really care about your costs, there are far more effective ways to save than fiddling with a bread machine.