50% energysavings through insulation of my old fridge with polysterene foam

Deutsche Version: Kühlschrank dämmen

Don't throw your old fridge, insulate your fridge!

fridge model: Siemens KT 15N00/05, bought in 1993
material cost for the fridge insulation: 25 Euros
cost reduction through energy savings per year: 27 Euros (119kWh x 0,23 Euro/kWh)

  1. Measuring baseline power consumption for at least 24 hours at a given room temperature. Extrapolating the result for a years energy consumption. In my case the old fridge took 247kWh per year at 22°C.
  2. Insulating the old fridge. Important: The condenser at the exterior (see how a fridge is built) must not be insulated as the air has to circulate freely around the condenser and around the fridge itself. The condensor might be integrated in the wall, in any case it gets warm when the fridge is running. Inside the fridge the evaporator must not be insulated, that is where the cold is coming from. Everywhere else i put insulation either on the outside or inside depending on what seemed more reasonable. I used foamed polysterene for fridge insulation. Outside: both sidewalls with 2cm thick polysterene and the fridge's door with 1cm. Inside: back (4cm thick) and ceiling (1cm). The polysterene / styrofoam insulation was fixed by special glue. The fridge's vegetable cooler was replaced by a removable thick self-made polysterene box which can be removed and replaced by the vegetable cooler again if desired. Furthermore, I disassembled the workplate of the fridge which was just hollow, put foamed polysterene into it and put the workplate back on top of the fridge. 
  3. Decorating. Covering the outer polysterene insulation first with a layer of thick foil to make the surface smooth. After that adding self-adhesive films. Covering polysterene box bottom inside the fridge with a white easy-to-wash plastic board.
  4. Measuring the temperature inside the self-made eco fridge. In my case the temperature inside the refrigerator was around zero degrees of Celsius though I did turn down the fridge's thermostat as much as possible. That was due to the new insulation which worked "too well". So far the fridge's power consumption was down to 180kWh per year. I could not get more energy savings with further insulation, instead the temperature dropped below zero. That meant that i needed to adjust the thermostat to the new efficient insulation. I opened the cover of the thermostat and did turn the adjusting screw anti-clockwise until I got around 6-8°C.
  5. Miscellaneous: I did some measurements which each in itself might not do much, still i might mention them here: Increasing the distance between the self-made eco fridge and condenser with thick discs under the screws that fix the condenser to the refrigerator. Cleaning the fridge's condenser. Checking the rubber seal insulation of the door: in a dark room, putting a switched-on torch into the eco fridge, closing door and checking for light coming through the rubber seal. If so the fridge's insulation is gone and one should change the rubber seal. Removing the grid at the top of the fridge's back for better air-circulation. This part of the fridge is not visible anyway cause it disappears under the workplate of the kitchen. Removing some bars of the fridge's front grid at the bottom for better air-circulation too. Circulation around the fridge should be as good as possible, cause the fridge's condenser needs to get rid off the heat. So keep distance on the side and back and top of the fridge.
  6. Measuring the self-made eco fridge's power consumption for at least 24 hours at a given room temperature. Temperature was now 18°C in my kitchen. At that temperature I did measure and extrapolate 105kWh energy consumption per year for my self-made eco fridge. Assuming that the eco fridge needs 5% more energy with every degree of higher room temperature I calculated 128kWh at 22°C room temperature. That is a low level of energy consumption for such an old fridge and equals energy label A+. That means the self-made eco fridge does save 119kWh per year just by adding insulation to the old refrigerator! 
  7. Sideeffects of insulating the old fridge: Less noise, cause compressor is running less often. Sustainability and environmental benefits. Saving energy and money: I dont count the working time because it was a pleasure to work on this project. After one year the cost for insulation will be paid back by energy savings. Every year that follows i save 27Euros with my self-made green eco fridge. If i would have bought a new green ecological A++ fridge same size and quality for 350Euros the money would have been paid back by energy savings only after 7 years and 9 months (A years power consumption at 25°C room temperature: 286kWh old fridge - 90kWh new eco fridge  =  196kWh x 0,23 Euro/kWh price/kWh = 45Euros/year savings. Take 350Euro for the new fridge divided by 45 Euro/year = 7,75 years.

In case you plan to make your old fridge green by insulating it yourself you must know certain things. Have a look here: thoughts about fridge insulation

Here you find a follow-up after 2 years: Check-up after 2 years

Insulated energy saving eco fridge
outside insulation: door, sides and top
polysterene insulation inside the self-made eco fridge:
backwall, top and styrofoam-box at the bottom