How to do an Energy Audit

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:

  1. A Kill-A-Watt meter, like this:
  1. a clamp on ammeter, like this:
  1. 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!


For energy auditing I’ve used this one (much cheaper then the TED meters and they do most of the same stuff)

It’s a whole house meter. Pop off 6 screws from your panel clamp on to the hots and you can monitor everything.
For me the most surprising load was the dvr; more energy then the fridge!!!
Best regards, David Baillie


PVR David?
Funny you brought this up Chris I have been watching my use pretty closely after going back on the grid for the winter. I have been averaging just under7 KWH a day for the past few weeks for home and shop. A few days ago I just turned the fridg back on a few days ago. This really made the meter spin for the first few days till it got up to temp. I was shocked and put the kill-a-watt meter on it last night at this time Just checked it tonight and only 1.21 KWH this last day now that ice bin is full and ice maker turned off. Power strip with modem ,router and laptop and phone charger drew a constant 52 or 53 watts when on and tested earlier this year while running off from the inverter. I have two odd ball blowers on the wood furnace in the shop. I just separated these this week to check usage an found the smaller one not correct for this furnace uses about 85 watts while the larger correct worn one uses 253 watts. Water heater is 110volt electric and I only run it a couple hours every other day. A load of laundry with cold water will add a couple kwh’s to a days usage. Electric dryer, did not run it at all summer but did this last week, vented in the house of course. when I had it turned back on they installed a new digital meter starting at zero. Makes it real easy to watch daily usage. I am afraid to look at it,I was pretty hard on it this weekend with a couple loads of laundry and the pizza oven that hasn’t seen much use for the summer worked overtime this weekend.

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Hey jim,
Bell calls it a dvr or “tivo” its To record your satellite TV shows. 24 hours a day she runs. It’s a point of marital friction but not worth “winning”. It runs on the grid connected side. That side totals between 5 and 7 kw a day. I might hit 10 a day if I’m electric heating the garage to above freezing. Propane hot water heater so we cheat there. Our place is weird since I have part of the house on solar part on grid. This time of year only the lights and circulator pumps run off grid, summer time I add on the freezer (300-400 watts per day) and uv water filter(300 watts per day).
Best regards, David Baillie

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Thanks for this. I had purchased a kill a watt a while back, but hadn’t figured out how to check the hard wired or 220 V stuff. So clamp on amp meter, DUH!
One thing I found funny was the phone chargers. They say to unplug the charger when the phone is done to save energy. Mine didn’t even draw enough to show anything on the kill a watt.
Electric bill says I average 22 Kwh per day. YIKES!!

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8 posts were split to a new topic: Wood heating regulations in the US

Good thread here Chris. For me it ties in with Steve U’s thread.
Last year I wanted to set up solar and the guy asked me, “How much energy do you use per day”? Well I lived in a 2800 sq ft house at the time moving into a 160 sq ft house. My answer was, “I have no idea what my needs will be.” So we set up a 1K system. In the Summer, the 1K system would be just fine, for me. The solar system charges up Eight 6 Volt batteries on our 24 volt battery bank.
Thankfully, I bought that little Kill-a-Watt and ran around my place here to see what everything draws. Anything that has a sole purpose of making heat with electricity, doesn’t get used. It goes to the flea market.
Prior to this week, we used a 1800W Ryobi twice a day for 6 hours at a time to charge our battery bank. Those 6 hours consumed 1 gallon of gasoline. That $5.20 per day with non-oxy fuel. About $150/month with no sun. No sun is what we get at this time of year because Mother Nature must feel we need a daily dose of snow flakes.
In January we will trade some snow days for subzero weather and sun.
Our biggest consumer of electricity is the TV. It is and older LCD that has vents on the top. I for one am not a big TV watcher but am married to one, especially in the winter months. So, what we did is took advantage of Cyber Monday for a new efficient model. Some battles are better left with a compromise.


I thought that might be a factor! How do they compare energy wise?

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I don’t have the new one to compare to yet. I will update you. I think it will be half or better.


The best change I have made now is switching out 100% on the houses to LED replacement bulbs.
The maligned wall-warts transformers are not that much of a problem for DIY energy making. Actually saves the electrical consumers from what may be dirty, unclean,sometimes off and on, DIY power.

Television. Sigh.Yeah. Our 63 channel Mom and Pop cable service collapsed two months ago. Wifie could not stand having no network channel news services and her home-improvement shows. I was plenty happy just DVD movies watching on the two older 150+250 watt Toshiba, and Sony CRT’s sets.
So . . . on-ward, and up-ward (in $'s and watts) to a satellite service now.
New lower wattage Sharp and JVC flat screen needed digital-tuners LCD sets; PLUS the satellite DVR base; plus the wireless in-house transmitter/receivers, and the total usage wattage is higher than ever for us.
Domestic peace has a cost. Do not ruin your chance for bliss stewing about this.
Ha! Ha! These satellite base needs are user programmable to a timed out no-change input inactivity period into lowest draw sleeps mode.
Down to a four-hour duration active settings now. (I blame the satellite company for the long reactivation re-loading times)

J-I-C Steve Unruh


You have me pondering Steve whether I can program in sleep time to the damn thing. Break out the kill a watt and punch some keys… See Chris great thread!!!

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OK, I moved a few posts around… yes, great thread. :wink:

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Here’s a follow up
Upon turn on of the 8 year old Westinghouse LCD TV, the Kill-a-Watt meter read 111 Watts. After it warmed up a bit, the reading leveled out at 107 Watts. The new TV I purchased on Cyber Monday arrived this afternoon. The Kill-a-Watt meter read 23.6 Watts. After the TV was on for a while, it remained at 23.6 Watts. This is without adjusting the brightness, so I could probably realized a lower wattage by adjusting the brightness.


Look into your outdoor lighting to save big time.

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Ha! Ha! Hard not to have really good information drift across topic lines.
BillS has said that his PV installed solar was 1kW. And that was adequate when the sun did shine late spring/summer/early fall. So at best probably a 6kW/hr daily input.
Said his 1800 watt rated Ryobi inverter unit had to be ran twice a day for 6 hours each session. Figure with unit warming up, battery bank charging/filling refusing more, higher input; then maybe a 12 kW/hr daily input. Higher needs makes sense with more hours of lighting needed in the winter.

My point.
You can audit your actual energy usage too by grid-disconnecting temporarily and then tracking how much power you need to produce to keep that now empty home energy bucket filled.
This may seem crude and unscientific.
But a very, very, cut-right-to-the-chase PRACTICAL way to find out your real uses versus actual needs.
Long haired woman in your home and a 1200-1500 watt blowing hair drier IS A NEED.
Ha! But no one, anywhere, will not experience some time Ma’ Nature imposing this crude-direct-find-it-out audit method onto you!

Best to be at least a little ready to make some DIY power regardless of the fuel source.
Needs-must will show you if you chose good-enough. THEN, improve to be able to more cheaply, longer duration fuel it.

J-I-C Steve Unruh