For me, the cooking co-op is a really life-changing system. Energy-wise, I have CFS, so walking around the corner a few days a week for a good home-cooked meal is a huge difference from shopping, preparing, cooking, eating and clearing up after a meal. Not to mention there's less risk of the burns, cuts and other general hazards of food preparation that are a daily occurrence for someone whose brain and body don't work as well as they should!
But if it weren't for that, I would still be very enthusiastic about the cooking co-op, and I'll tell you for why. I am constantly broke, and the cooking co-op saves me bucketloads of pennies.
Cooking a meal for myself, something simple and sensible like rice with stir-fried vegetables, costs me about 15-20p in electricity, according to my smartmeter that I got free from British Gas. Cooking for five people costs me about 20-35p for the same meal. Supposing the cooking co-op happens on all five possible days of the week, that means I save that solo-cooking amount on four of the days, in exchange for the five-people-cooking amount on one of the days. This leaves two days of ordinary solo-cookery. Ie:
Monday: Co-op cooks for me, £0.
Tuesday: Co-op cooks for me, £0.
Wednesday: Co-op cooks for me, £0.
Thursday: Co-op cooks for me, £0.
Friday: I cook for the co-op, £0.35
Saturday: Solo cookery, £0.20
Sunday: Solo cookery, £0.20
So in one week, instead of paying [Solo cookery x 7 =] £1.40, I actually pay the above-calculated amount of £0.75, and I save just under half. That's a saving of £2.82 per month, or £33.80 per year. How awesome is that? (It doesn't sound like much, but every penny helps me. 50% of my electricity goes on my fridge and I don't really use it.) And that's just electricity; it's a lot more when you factor in that buying in bulk is cheaper, and when you're cooking for more people there's less food wasted, and less packaging...
I'm not going to calculate the carbon produced, 'cos I think that is a fudging stupid system. That is a long story, but this amusing video goes a little way towards explaining why.
In summary: Start a cooking co-op.