The factors affecting the power consumption of a fridge or freezer can be broken down into 4 broad categories:
Fridge Design: This is a very important factor when it comes to energy consumption. Unfortunately, it cannot usually be easily modified by the end user.
Positioning: In some circumstances the fridges position can be changed.
Usage patterns: Determined by users.
Maintenance: Determined by Users
Each of these broad categories can be further broken down.
This is probably the main factor in energy consumption. Unfortunately, fridges are normally built to a price and not a performance level. Such factors include:
The thickness (and type) of insulation in the external walls of the fridge. I remember an add for one brand of fridge 6 or 7 years ago which had as one of it's selling points: "Look how thin the walls are". The worrying thing is that it was one of the most effecient fridges on the market at the time!
The effeciency and positioning of the compressor pump. The pump is normally located at the bottom of the fridge. Most of the pumps are quite ineffecient and get very warm (Too hot to touch for more than a second or so). What happens to the heat these pumps give off? As hot air is prone to do, it rises and warms up part of the cabinet immediately above it. This heat finds its way into the fridge, which means the compressor has to work harder to get rid of it, which means it heats up more etc etc.
Defrosting method used. Cyclic defrost models have a low wattage heater in the evaporation plate which is meant to turn on & off as required. With my fridge, the heater appeared to be on most of the time the compressor was off. Frost-free models have the heaters inside the walls of the fridge.
Exposed Condenser coil at rear or 'clean back': The newer 'Clean back' fridges normally have the condensor coils built into the rear and side walls, providing a larger area for cooling than those with the condensor coils exposed at the rear. Also, because they're not exposed, they don't gather the dust that reduces the efficiency of exposed coil models. Note that some new smaller fridges (220 litres and less) still have the exposed coils at the rear. Also note that it may be possible to add extra external insulation to the models with the exposed rear condensor, but not the 'clean back' models.
The quality and condition of the door seals. This is also an ongoing maintenance issue
Fridges should ideally be in the coldest part of the house, with good air flow around them. Unfortunately, the kitchen doesn't normally fit into this category. (How often have you seen a dedicated 'fridge cavity' located beside a stove?) Some suggestions to consider where appropriate:
Encourage air circulation around the fridge. This may involve moving the fridge out a few cm from the walls, or elevating it a little to facilitate natural air flows. A solar (or normal) fan could be installed near the compressor to improve air movement. If the house is elevated, a hole (with appropriate vermin protection) could be drilled under the fridge, which would draw cooler air up from under the house. Another warm air exhaust to the outside could be installed above the fridge.
Organise things in the fridge, so you don't have to stand there with the door open for long periods while you search for that elusive jar. Temperatures vary in some fridges, so things that need to be cooler could be placed in the cooler parts of the fridge. (Use a fridge thermometer to find the cooler parts).
Only refrigerate what needs to be refrigerated. Things have a habbit of gravitating into the fridge when they don't really need to be there. It may be appropriate to refrigerate some things in summer, but not in winter. Think about what you're refrigerating and why.
Do things like drinking water really need to be refrigerated? Why not leave a water container out on the bench. If people want water or other drink cooler than the ambient temperature, use an insulated flask with eaither cool water/drink and/or ice blocks in it. At least then you'll only have to open the fridge once every few hours for cold drinks rather than every few minutes....
If you have large empty spaces in the fridge, fill them up with containers of water. This way, when the fridge door is open, less of the cold air will 'fall out'. This also adds to the thermal mass of the contents, which helps maintain a steady temperature inside the fridge. Note: Adequate room should be left around containers for the air to circulate, so don't cram everything up too tightly.
Check the temperature inside the fridge/freezer with a thermometer. Note that different temperatures may be recorded in different positions. Adjust the temperature dial so the correct temperatures are achieved (Normally a max of 4°C for the fridge, and -18°C for the freezer). Note that internal temperatures can vary with external temperatures, so the dial settings may need to be changed from time to time.
Check that the door seals are clean and in good condition. Check that the door is sealing properly.
If you have a fridge with exposed coils at the back, dust them down from time to time.
Check that there's not a build-up of ice around the fridge/freezer. Defrost if necessary.
My Fridge & Freezer
The graph to the right demonstrates the combined power consumed by my fridge & freezer with varying ambient temperatures. The graph is a 'best fit' line of data taken over a six month period. Two people were living in the house during this period.
Fridge: 330 litre upright fresh-food only (no freezer) with exposed condensor coils at rear. Purchased 1994. Quoted power consumption: 490 kWh / year
Freezer: 220 litre chest freezer. Purchased 1994. Quoted power consumption: 350 kWh / year
The fridge has been modified slightly: The cyclic defrost heater has a switch in series with the heating element. I leave this switched to off most of the time. This has reduced the fridge power consumption by around 300 Wh /day (Approximately halved it's consumption in Winter from 600 to 300 Wh/day).
Last Updated: 06/02/03