How to reduce your refrigerator energy usage without breaking the bank

Did you know at 12 cents per kWh it costs roughly $140 every year to run a ten year old refrigerator? And you can almost double that cost if you have a secondary fridge running in the garage or basement. The fridge is one appliance, however, where Canadians can easily save energy. With this simple and cost effective method that any handyman can do themselves, you can reduce your refrigerator’s energy usage without breaking the bank.

All you need to do to keep your fridge cool for a fraction of the cost, is bring a bit of the cold air in from outside. There is a little more to it than that, but all you need are some air filters, aluminum duct work, insulation, an exhaust fan, and a working knowledge of fluid mechanics and heat transfer.

The energy savings stem from the second law of thermodynamics: if you have two environments at different temperatures they will naturally want to reach an equilibrium temperature. In order to keep the temperature of a fridge cooler than your house, the fridge must do work.  The compressor at the back of the fridge circulates a refrigerant between the interior of the fridge and the household air. This compressor takes a lot of electricity to run, perhaps 100 W or more, but that’s the thermodynamic cost of refrigeration. The air outside, however, is already cool if it’s winter. All you need to do is circulate it through the fridge cavity until the temperature stabilizes. And all that you need to do this is a simple fan.

There are a few things to consider when selecting the fan. The fan must overcome the pressure losses in the system if it is to bring cool air at a reasonable rate. These pressure losses typically consist of static pressure losses due to pipe friction and airflow resistance through the filter. Other than that, the most important thing to consider is the dynamic pressure associated with the flow of air. The power consumption of the fan selected in my design was 90W. That is a respectable difference between the typical compressor power consumption.

By supplying your fridge directly with cold air you will undoubtedly reduce your energy use by approximately $20 per year, assuming 4-5 months of reasonably cold weather. The price of materials shouldn’t be more than $110, which means this energy saving upgrade will pay for itself in 5 years. And since refrigerators typically last 20 years or more, this simple DIY project will save you money on the electricity bill for years.

Filed under: Students on Sustainability