Originally Posted by FUEGO
As far as cycling the fridge, I can't imagine a 3 hour outage from 4-7 would result in a high temperature gain. Maybe 5 degrees if you aren't opening it much? Food might spoil slightly quicker, but being at the target temp the other 21 hours of the day would prevent any significant increase in spoilage.
I think food spoilage could be a real risk. It's been a long time since I looked at any chemistry, but as I recall reactions could double their rate with only small (linear) increases in temperature -- I'd be surprised if that didn't also apply to bacteria growth.
According to FDA (Power Outages: Key Tips for Consumers About Food Safety
) "Refrigerated food should be safe as long as the power was out for no more than 4 hours. Keep the door closed as much as possible." -- The OP is talking about 3 hour outage which is shorter than 4 hours, but I assume he wants to do this everyday which would substantially increase risk.
There may be some "safety factor" in the FDA rule, so it might not be too bad. I'd probably be okay with power outages on a repeated basis for some foods like vegetables, cheese, etc. But I don't think I'd be willing to risk it if I had any raw meat in the refrigerator portion.
But is it worth it to save the 11.5 cents per kWh three hours per day for five months of the year?
Having had food poisoning before, I wouldn't do it personally.