Energy Conservation / Renewable Resources17 Sep 2008 10:04 pm

According to an energy audit I did last year, our hot water heater comes in (a distant) second in electricity consumption in our house, accounting for about 7% of our total use (our heat pump for central heating comes in first at ~40%, averaged over all seasons).

Since a timer to shut off a water heater during off-hours is pretty cheap (~$30), and I’ve read that using one of these is an effective way to cut energy consumption, I decided to get one. I got around to installing it this last weekend:

Timer for our hot water heater

Right now it’s set to turn on a couple of hours before we get up, then turn off once everyone is out of the house in the morning. It turns on again in the evening for dishwashing and nighttime showers. All told, it will be on for about 8 hours a day. It has a manual switch that allows you to easily override the timer (say on the weekend, if you need a shower in the middle of the day); we just need to remember to hit the switch ahead of time.

Unfortunately, since the heater is on a 240 V circuit, I can’t trivially measure its consumption over long periods of time (like I can for appliances using a Kill-A-Watt). Yeah, I could wire something up to do this, but I’m not willing to put that much time into this investigation¬† ;-) ¬† For the time being, I’ll have to judge effectiveness based on our total electricity consumption…

[My earlier audit was based on estimates of power consumption for the hot water heater and heater combined with measurements of most household appliances, tweaked to match actual consumption numbers from the power company.]

Something worth noting for the DIYer: I’ve done a modest amount of electrical work using 14 ga wire for typical circuits (ceiling fans, lights, etc.). This installation required 10 ga wiring, and the switch itself required working in some pretty tight areas. I had no idea how difficult it would be to wrestle this heavy wiring into place in those conditions… yikes!

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