The 3 kWh Challenge

After a poor April (with no year-over-year change in our electrical consumption), we got a new refrigerator and reevaluated our strategy. Reducing our furnace use helped a lot in the winter, but we barely used the A/C last year, so that wasn’t going to improve this year.

Thanks to the refrigerator, May was a good month. We were able to reduce our consumption by 50%! That brought our total usage for May to 121 kWh, which is a little over 4 kWh a day. Given that, I talked Maggie into trying to reduce our usage to less than 3 kWh a day in June. For comparison, leaving two incandescent bulbs on would use up the allotment for that day.

So June is over; how did we do? From June 1st to July 3rd, we used 79.9 kWh or a little under 2.5 kWh a day! Here’s how we did it.

No A/C – A/C isn’t as energy intensive as heating, at least in part because the temperature difference isn’t as high, but it still uses a lot of power. Running a typical central air system for half an hour can use over 1 kWh. Instead, we used blinds to reduce solar gain, opened windows when it was cool and closed them when it was hot, used the ceiling fan and window fans, and, on one particularly hot afternoon, took refuge in an air-conditioned movie theater.

No hot water – the majority of residential energy use is cooling and heating, including water heating. My best estimate is that our 40-gallon water heater uses 300 Wh (0.3 kWh) a day. We got a solar camp shower and we’ve also taken some cold showers. As a bonus, we cut our water use significantly since you don’t dawdle in a cold shower!

No clothes dryer – Our clothes dryer runs about 2 kWh per load! Now that it’s summer, we’ve avoided using it entirely and line dry everything. It takes more planning, especially since we had so many thunderstorms in June, but that’s quite the energy savings!

Reduced computer use – I have a small netbook that uses less than half of the electricity of my normal laptop. I was able to get even better numbers by using Windows’ power settings to dim the screen and slow the processor. I also made sure to take my charger with me when I worked outside the house. That doesn’t decrease my overall electrical use, but partly offsets the fact that I work from home.

Sharing space – In the evening, Maggie and I make sure we spend most of our time in the same room. That means we’re only running one fan and one set of lights. It’s not a big savings, but it’s also pretty easy to do.

We won’t be able to sustain it into the winter, and some of it is extreme enough that we might not be able to sustain it for more than a month or two. I think we’ll be able to keep it under 3 kWh for July and maybe August, but when it gets cold again, we’ll have to turn on the furnace. We also won’t be able to stop using the dryer entirely at that point. Still, for now, we’re feeling pretty good!

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8 Responses so far »

  1. 1

    Emily said,

    July 12, 2010 @ 2:22 pm

    Is your stove gas or electric? I think we do all these things (except the “no hot water” one) and our daily usage (minus hot water, which is on a separate meter) is about 7kwh/day. But our stove is electric, and so’s the well pump. Where are those watts going??

  2. 2

    Will said,

    July 12, 2010 @ 4:57 pm

    Our stove and oven are gas, which helps a lot. An energy-efficient stove and oven might use 1-1.5 kWh per hour. An inefficient one might use two to three times that much. Unfortunately, they’re 220v, so you can’t measure them with a Kill-A-Watt. Your best bet is to find your model information and see what the manufacturer says. If you can’t do that, you can estimate by measuring your meter right before and right after you use the stove or oven. Remember to subtract out your base load (at 7 kWh a day, subtract 0.29 kWh per hour). That should give you a ballpark figure, assuming you weren’t running a clothes dryer or anything at the same time.

    If it’s not all your stove and oven, you might have some other inefficient appliances (washing machine, dishwasher — which we don’t have, computer, refrigerator, etc.) or you might have something that’s drawing power when it doesn’t need to be (lights, computer, cable box, etc.).

    If it is primarily cooking that’s causing the increase, you can try to cook more efficiently (cook multiple things in the oven at once, turn off the heat a little early, use a microwave to boil water), use another option when possible (a toaster oven uses a third or less electricity than even an efficient stove top), or skip the stove and oven entirely! In the summer, solar cooking and grilling are both good options.

    I’d love to hear a follow-up once you’ve had a chance to examine your situation a little more closely!

  3. 3

    Will said,

    July 12, 2010 @ 5:02 pm

    Oh, I also forgot to mention that a well pump can draw up to 2 kW, depending on horsepower, as well. If it runs for half an hour a day, that’d be an extra 1 kWh!

  4. 4

    Emily said,

    July 13, 2010 @ 10:22 am

    Thanks…this is good to know. I know our radon fan uses 2-3 kwh/day, but we turn it off in the summer when we have all the windows open and the fans on. That’s the bulk of our summer/winter electricity disparity. The well and the stove, we can’t do a lot about. We do cook some with the solar oven, and we do all the “cook things together” and “use the toaster oven instead of the big oven” whenever possible.

    I’m considering a newer, more efficient range that has 2 ovens, since the majority of what we bake is homemade pizza. Too big for the toaster oven, but flat and doesn’t need to heat up the whole big oven, either. But that’s a new appliance…hmm…

  5. 5

    Maggie said,

    July 14, 2010 @ 9:35 pm

    You could also consider building a cob oven for outside pizza cooking (I haven’t done one but a few of my friends have them and love them).

    http://www.greeniacs.com/GreeniacsGuides/How-to-Build-a-Cob-Oven.html

  6. 6

    Powering Down | GreenCouple.com said,

    October 31, 2010 @ 8:44 pm

    […] couple months ago, Maggie talked me into giving a presentation at the Simply Living Fair about our 3-kWh Challenge (which has more details, if the presentation is too high-level for you). The presentation went very […]

  7. 7

    Eric said,

    June 15, 2011 @ 5:02 pm

    Out of curiosity, which fridge did you get? There are some which are not very expensive and go far beyond Energy Star requirements.

    FWIW, here’s a family of 4 that made it in under 200kWh in a month:

    http://solarchargeddriving.com/editors-blog/save-more-for-the-ride/695-can-a-family-of-4-use-less-than-200-kwh-a-month.html

  8. 8

    Maggie said,

    June 17, 2011 @ 8:22 am

    We got an Electrolux/Frigidaire FRT21IL6JW2. I’m sure there are better models out there but this was the best we could find at our local Lowes – and it was on sale. We debated trying to special order a super efficient fridge but our old one was so bad that this one is a wonderful improvement.

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