Monitoring your energy usage

I recently went through the entire house, made an inventory of every electrical device in the house, and measured its energy consumption.

You should do that too.
  • You'll find out how many things consume more energy than you thought, and you can easily reduce your monthly energy bill without much effort.
  • In my case, I was preparing to go solar, and you'll want to reduce your energy consumption before doing that. For roughly every 40kWh that you can reduce your average usage, you'll save around $1,000 in the cost of your solar system if you buy the system outright.
What you need

A simple electricity usage monitor. Just search for them, there are tons of them out there going for around $25 or so. I got the Ensupra Electricity Usage Monitor, but any of them will do.

I also recommend a label printer. You should have one in your house anyway.

And finally, pick your spreadsheet application of choice. I used Google Sheets (i.e. the spreadsheet solution that comes with Google Drive), and you're of course free to use Excel or LibreOffice Calc. Try to use something you can edit from a mobile device, be it a laptop or cell phone.

The actual design of your spreadsheet is completely up to you, but for your convenience, I made a template that's ready for you to use. We'll get to it in a bit. Click here to check it out - choose to "Make a copy" to create your own copy to edit and work with (or, if you're not logged in with a Google account, you can download it as a file to use offline).

Take inventory

Go through your house, plug the monitor into every single outlet and measure every single device. Don't skip anything. As we'll discuss below, there are lots of little things that may surprise you.

Measure several states: I generally differentiate between "idle" state and "active" state. Idle is the device being plugged in but not in use (like a TV on standby, or a battery charger without a battery in it), and active is the device doing what it's supposed to do.

Things can of course not always be easily classified into those two, so use your best judgment and get average values.

For every single device, make an entry in your spreadsheet. Also, create a label that you will either stick on the plug or the cable near the outlet. The label should identify the device, it's idle and active usage, for example:

The nice side effect of this is that you'll be able to easily identify a cable that's plugged into a surge protector with 10 other things.


Now let's look at the sample spreadsheet. These are real-life values that I measured in my home.


You remember how you were always told to turn the lights off when you leave a room? Lighting is a huge electricity waster, that's well known. However, replacing your lights with LEDs can be a great investment. Today's LEDs are effectively indistinguishable from incandescent lights. I replaced all our recessed lighting in the kitchen, 8 bulbs at 65W each, with these guys here: Phillips Soft White 13W. They're fully dimmable and have the same light temperature.

That alone saves 9 bucks a month if you were to leave the lights on 4 hours a day.

Little big devices

The cable box was probably the biggest surprise. 19W, even when in standby mode! You're paying $2 per month for your cable box in addition to your cable fees! I happened to cut the cable around this time, but if you plan to keep watching TV, you should definitely consider unplugging this thing while you don't use it.

In the spreadsheet, you'll see several lines where the recommendation was to "unplug" - that can be pretty annoying, but I made it easier by getting switches and switchable surge protectors.

Again, there are tons of choices out there. I settled for Belkin switches and this switched outlet. There are also Belkin switches with timers, that would be a good compromise for things where the outlet is hard to reach.

The spreadsheet also lists a charger for a hand vacuum that constantly drew 6.5W - I could even feel that the vacuum got quite warm even though it already had a full charge. Not to mention that some rechargeables don't appreciate constantly being charged. So - unplug your chargers once they're done.

Unplugged, idle, active

You can use the spreadsheet to play with the numbers. Compare what you currently have with what you could do and how much that would save. In some cases, simply putting something to standby mode is good enough.

I often left my projector running even after I stopped watching something (mostly because the projector takes a while to cool down and can't be turned back on again during that period), but even an hour or two a day comes with a substantial cost. Just going to idle here is good enough. In the spreadsheet, take the hours off the "active" column and add them to the "idle" column to reflect this.

In other cases, even having something in idle is wasteful, so you'll need to unplug it. My printer for example eats up 3.2W even when idle. So I'm turning it off entirely when not in use. See how I took the hours off the "idle" column to indicate that.

If you want to go all out

There are really fancy solutions if you want to go all the way. You could get something like the Rainforest Eagle, it monitors the energy usage in your home in its entirety and creates a graph that you can then analyze. It's great, although a bit finnicky to use if you have a solar system because you then have to add the amount of energy generated with the panels to get an accurate picture. It's still useful though - let's say you have a device that you cannot monitor with the Ensupra monitor. So you look at your usage at night when the solar panels are not generating juice, then turn the device off and monitor your usage again. The difference is how much said device consumes.

The Eagle's data can be fed into external sites like, which can combine that data with your solar panel generation.

The Ensupra can be used to measure things that routinely turn on and off (like a refrigerator) - you plug it in for 24 hours and then do the math. If you're looking for something more elegant, try the TP Link Smart Plug. It's similar to the Ensupra in that you plug it between the outlet and your device, but it does a lot more - it will connect to your WiFi network and allow you to check the usage stats with a mobile device. Of course, you can also program it to turn on and off at certain times, or switch it on and off through the app or the web.

You can go crazy with this, it all depends on how much money and effort you want to spend on this.

It all adds up

See how all the things from the spreadsheet save $16 per month if you pay $0.18 on average per kWh. And that's not even fully accurate, SDG&E has a tiered model where you pay substantially more (upwards of $0.35) once you exceed certain levels, you could save even more.

Or, if you're planning to go solar, the specific plan outlined in the spreadsheet would reduce the average usage to a point where a solar system could break even with two fewer panels on the roof! This might save about $2,000 off the price of the system. How much the panels will actually generate obviously depends greatly on your climate and what kinds of panels they are.

Whether you want to switch to solar or just save on energy, this is a little afternoon project worth doing. Even if you ended up not saving a damn thing, just labeling all your power plugs makes the whole endeavor worthwhile.