- Thermal Audit
What does it cost to operate?
You want to determine the value of replacing an old appliance with a new one. For example, you have a refrigerator manufactured in 1984. Since you don't have a kWh meter, you look in the table below and get 1457 kWh/year for the average refrigerator sold that year in Canada. The new appliance has a label claiming it uses only 410kWh per year. The potential savings are 1457 - 410 = 1047 kWh per year.
The annual cost savings are 1047kWh * $0.10/kWh (your power rate) = $105
Assume the new refrigerator will last 15 years. Assume you can sell the new appliance 15 years from now for $100. Using a spreadsheet or financial calculator, you next determine the present value of saving $105 a year for 15 years and then selling it for $100. In Microsoft Excel, the formula would be =PV(0.07,15,105,100) and it will yield $993. The link below will also calculate this for you.
Appliance Savings Calculator with database lookup This means that spending $993 on this new refrigerator now will yield a return of 7%, which is the average growth of the stock market over the last 200 years. If you can get the refrigerator for $993 or less, then it is a good use of your investment dollars. If you pay more than this, then your money might have been better invested elsewhere.
The table below of actual values (as opposed to government averages) will grow as I have time to collect more data. The intent is to be able to make accurate economic decisions about appliance replacement.
Average appliance energy usage (from EnerGuide). These averages are good for general estimates of what an older appliance might use. See below for actual, real world measurements.
|Annual kWh||1984||1990||1997||1999||2004||energy star|
|Standard clothes dryer||1214||1103||887||908||912||413|
|Self cleaning Ranges||790||727||759||742||622|
These are actual kWh readings from appliances. It is important to figure out what draws the power you pay for every month, so that you can make informed decisions about where to direct your efforts. Many devices are intermittent (like a refrigerator that cuts in and out) and seldom draw the "rated power" listed on the label, so determining usage requires electrical test equipment.
For simple devices like light bulbs, multiple the wattage times the hours of usage and divide by 1000 to get kWh. For example, a 60W bulb running for 10 hours burns (60W x 10hr)/1000 = 0.6kWh. For complicated things like dishwashers, computers or refrigerators you need a kWh meter to monitor it over time. Since most people don't have a kWh meter, we started this reference list. Please feel free to contribute to it -- you can send us your measurements via the "contact us" form.