We have a fridge/freezer in an unheated garage in Md.
We had problems with the freezer in the winters. Kenmore came out and said that it had to do with the thermostat being controlled in the fridge section so that when outdoor temps dropped, the temp in the refrigerator was cold enough so the condenser would shut off so the stuff in the freezer would start to thaw.
Not sure how it would work with a freezer but seems like it may shut off and on a lot due to outdoor temps.
Here is a note on installing them in garages. Perhaps there are some models that are designed to operate effiiiently at lower temps but seems like the majority would not:

Note: manufacturers do not recommend you keep a freezer in the garage or any other outbuilding, as it may have to use much more energy. Most models require a minimum ambient temperature of 10°C (50°F) to operate efficiently. If the outside temperature is any lower, the freezer will struggle to keep your food chilled  it may even start to defrost. If it does break down, the appliance may not be covered by the guarantee.

We've had our 25+ yo chest freezer in our garage for over 13 yrs now. We live in a northern climate with below freezing temps for much of the winter. I have no idea what our energy consumption is with this set-up, but we have no problems with performance.

Joanna,

There is a problem with new units in below freezing conditions. I've been told by a salesman that it has to do with the new refrigerants used because of EPA regulations. If I have this correct, the new refrigerants liquify at higher temperatures, so the compressor doesn't work at temperatures below freezing. We're trying to replace a 50 plus year old freezer that is in our garage and having a problem. We may end up having to keep it, until it dies. There is one freezer, called a Gorilla that is supposed to work in unheated conditions. It's unfortunately out of our price range.

Petro