Home Electricity Audit
This post describes how to do a room by room home energy (electricity) audit. This is a do-it-yourself audit and requires some basic spreadsheet and algebra skills. It also requires some sort of tool to measure energy use of individual appliances. I used both a kill-a-watt meter and a home energy monitor to help me make the measurements. This audit is not meant to replace a professional energy audit but should be used in conjunction with a professional audit. The purpose of this audit is hunt down the biggest energy users in your house as well as find any phantom loads (aka. vampire loads).
- Download this example spreadsheet, or create your own. You will need to modify the spreadsheet to represent the lights, electronics and appliances in your own house
- Obtain a kill-a-watt electric usage meter or similar device. The kill-a-watt measures voltage, current, energy, and power of individual appliances and components.
- Optional: Install a home energy monitoring system. This is not necessary for the audit, but will make some measurements easier.
Room by Room Audit
Go from room to room measuring the energy usage of all lights, electronics, appliances and anything else that uses electricity. For each room:
- Enter the power rating of each of the lights in the room and then enter an estimate of how long the light is on each day.
- For each plug-in device:
Some exceptions to the above:
- plug the kill-a-watt meter into the wall and then plug the device into the meter
- Push the "Watt" button on the meter to measure power usage
- Turn the device on and record the power measurement
- Put the device in standby mode (if applicable) and record the power measurement
- turn the device off and record the power measurement
- If the device has more modes, measure the power for those modes as well
- For all modes, estimate the how long each day the device is in that mode and enter that into the spreadsheet
- fridges and freezers: You are better off using the average kWh rating which you can typically find posted inside the fridge or freezer
- oven, dryer: In Canada, ovens and dryers run on 240V, so the kill-a-watt is incompatible. You can either use the average rating for your oven, use a clamp on electric meter, or use your home energy monitor to measure power usage when on and then when off. The difference is the power usage of the oven.
- central or baseboard electric heaters, electric hot water heaters and air conditioners
- The easiest way to measure these is to use a home energy monitor
Now admittedly, the total energy use that the spreadsheet tallies for you is an estimate because it is based on your approximations of how long each device is on. That is okay though because the two main things you will learn from this audit are which devices in your house use the most energy and what your worst phantom loads are. These two pieces of information can help you shape your overall energy plan by identifying what devices you should try to use less and what devices you should actually unplug when not in use.
When I did the energy audit on my house, these are the conclusions I came too:
- I should hang out my laundry to dry whenever possible. My dryer draws 5000 watts when in use. I've started hanging towels and sheets because they are the easiest to hang and take a lot of volume out of the dryer. Many new dryers use a humidity sensor that turns the dryer off when it senses that the clothes are dry. This is a great feature because it will ensure the dryer only runs as long as it should.
- I should set the thermostat fairly high for the air conditioning (I use 27 or 28 C). My a/c draws more than 2500 watts when turned on.
- I should turn off the switch on the power bar at my desk. The combination of monitor, computer and printer draws about 20 watts when everything is turned off.
- My two cable boxes draw 50-60 watts when switched "off". I should put these on a timer to turn off over night.
I've had several of my classes go through this home energy audit, and it is a constantly evolving process. If you have any comments or suggestions on how to improve the process, the spreadsheet or whatever, I'd love to hear from you.