It’s one of those things everybody should do occasionally. An “energy audit” just means you go around the house and add up all the things that plug in and use electricity. Find the lurking energy hogs. You’ll learn a lot!
You need:
- A Kill-A-Watt meter, like this:
- a clamp on ammeter, like this:
- A notepad, or a spreadsheet.
For most things, you’ll want to note the idle wattage (plugged in but not “working”), the startup draw (usually motors/compressors), the stable running wattage, and the average usage over 24 hours. Some things you don’t need so much detail, but many things will be high-power and very intermittent, or low power but running constantly. For some things like laundry, you might want a per-load usage too.
Some things are hardwired in, or use a 220v plug, so you can’t use the Kill-A-Watt meter. This is where you use the clamp on ammeter, to measure amperage. Find a place in the wire where you can separate the conductors, and place the clamp only around the hot lead. Multiply by the voltage (read that from a nearby regular socket using the Kill-A-Watt meter) and you’ll get a reading in volt-amps (VA), not the same as watts but close enough for our purposes. Check the nameplate on the appliance for a sanity check - it should draw close to what it says on the label.
Once you’ve annoyed everybody by unplugging everything and resetting their clocks (ha!) it’s time to run the numbers. You can do a lot with what you just gathered.
1) Uncover the energy hogs! You probably have at least a couple of surprises on your list. For example, today I learned that our gas powered stove, an “non electric” appliance, was nevertheless plugged in and uses minimal power to run the clock, the timer, etc. Even the sparker that lights the burners has a negligible power draw. BUT - when the oven was started, it starts pulling 350-400 watts, and stays there! This amount of electricity could cook dinner all by itself, in a crockpot. What is using so much power in a gas oven? Answer: The igniter, a thermal resistance device that gets hot enough to ignite gas, and apparently ours stays on for the entire heating cycle, entirely unneeded once the flame is lit. Older gas ovens used a simple pilot light, but this is more, um… efficient.
Another biggie is the freezer defroster. Ours draws a massive 750w, for a minute or two, every few hours. This is no big deal on average, but could throw a limited power budget into overload, if not accounted for. The compressor itself starts at 300w, tapers down to 120w, and runs about 50% of the time. Average wattage over 24 hours is about 75 watts.
2) Plan a limited power setup. Limited in either maximum draw (generator) or daily consumption (batteries). Even if you haven’t got an off-grid solar or woodgas power scenario, try just determining the essentials to have running on backup power after a storm. Another example, I added up all the lighting we use, which I just finished converting to LED. Every bulb in the house at once, would be 250w, a “normal” ie not very conservative usage would be around 100w at night. This means, whatever else I plan, having adequate light is very easy and I can pack away the tea candles.
A different kind of “limited” power plan might be household wiring issues. The initial reason we converted to LED, was that my previous energy audit revealed that every single overhead light in the house was on the same circuit… old cloth wrapped wire from 1940, in the ceilings and no way to replace it. Running incandescents on this is asking for trouble. But as mentioned, our maximum draw is now so low, I don’t care how many lights get turned on, we won’t burn the house down.
3) Actually change your energy habits. It can be shocking when you add it up, and realize the electric clothes dryer is 1/2 of your electric bill. For something with a simple and free solution, you are paying cash money. You might be visualizing dollar bills blowing out the dryer vent. Or maybe you choose to pay the cost for the convenience - at least you can make an informed decision.
The biggest change for me, this round, will be a switch from constant-on desktop computers, which use a steady 100-150w, to occasional desktop use and more reliance on my 10w laptop. They get the same internet-ing accomplished, and while the laptop is less “powerful” it’s also 10x more efficient with power.
In the rest of this thread, I encourage you all to run and report your own energy audits, especially if you learned anything surprising.
You off-grid people probably already know your usage down to a “T”. Enlighten us!
