Fridge

In which I record the temperature of my fridge and surrounding environment, and track events that take place involving the fridge, in order to answer the question, "Can I unplug my fridge at night without ruining my food?".

Update: It turns out turning off your fridge is bad for it. Details here.

All events involving temperature changes in the home are recorded. Click on the vertical gray bars to get detailed information about each event.
The first 24 hours are a the baseline.
During the night of the 14/15th, I unplugged the fridge from 2300 to 0800, and the temperature rose from the baseline to 9 and 10 C for the back and door, respectively. The freezer rose from -20 C baseline to -4 C.
During the 2nd day (April 15), I added a bunch of liquid to increase the thermal capacity. The addition is visible by the spike at 1845 and the note at that time. Unfortunately, the liquid was added too late in the evening, it did not cool, and it therefore acted as a heater during the night. The temperature rose to 9 and 11 C for the back and door.
For the remaining time, April 16, 17, and 18, I did not unplug the fridge. The temperature variation is slightly less, especially near the front of the fridge (green line, door), due to the added liquids.

upstairs, downstairs, outside, fridge door, back of fridge, freezer. Download the data: top, bottom, and event log.

This is part 2 of the above experiment.
Different dates, no events recorded. Only recorded temperature for fridge door and back of fridge.
The first two nights have roughly the same liquid that was added on Fri, 15 Apr 2011 18:45:00 GMT (see above graph). This liquid acted as a heater the first night.
Here it has equilibriated with the fridge temperatures, and the maximum temperatures at 0800 after unplugging the previous night at 2300 are 8 and 10 C, rather than 9 and 10 C.
A small amount of additional liquid was added the afternoon of the 20th, and the temperatures drop by 1 C to 7 and 9 C for the last two days.

The mean normal value in the door is 5.0 C and at the back is 2.6 C.
Calculating the area under the last curve, less the mean temperature, there is a positive thermal anomaly of 25 degree-hours for the door and 28 degree-hours for the back of the fridge. (1 degree above normal for 1 hour is 1 degree-hour.)
We note that food decay is non-linear, so degree-hour is not the best unit to explain the additional heat. For example, 1 hour at 10 degree will spoil food faster than 10 hours at 1 degree, but both compute to 10 degree-hours.

Conclusion: With enough water (or steel blocks) acting as a thermal mass, it is safe to unplug the fridge at night. Meat or fish should be consumed quicker than if the fridge stayed plugged in. Any meat or fish should stay in the fridge for 1 night maximum.