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December 20, 2007

Four simple ways to keep your water hot, and reduce your carbon footprint

In a recent look at my hot water heater, I discovered that the gas burned to heat my water is responsible for 8.1% of my CO2 emissions, or 1.5 tons of carbon a year.

It took me some time, but I tracked down the manuals for my hot water heater and was able to learn a number of things about the system that sends hot water through my home.

My natural gas hot water heater is pretty much a super-sized version of heating water on a gas stove. Cold water comes in a pipe and falls to the bottom, while the hot water rises and gets sucked out a pipe in the top.

Unlike a pot on the oven, though, hot water heaters are a little bit smart. If the water temperature inside the hot water heater is a high enough temperature, it will shut down the heat source for a while. Aha! Breakthrough!

This means that to keep the hot water heater efficient, the end goal is to keep the already-heated water hot for as long as possible. The less that burner operates, the better. Armed with this knowledge, I decided on four minor projects for the hot water heater:

1.  Turn down the temperature on the hot water heater
I can't tell how high the heat is set on my hot water heater, because it is labeled with red triangles and letters. I've turned it down some, and will experiment at what is the lowest tolerable level. The recommended temperature for efficient hot water heaters is 120 degrees F.

This took about five seconds to do, and should reduce my carbon emissions by 5-10%. Not only does the water take less time to heat, but the temperature can fall further before it needs to reheat. This is saving energy and preventing carbon from entering the atmosphere.

2.  Adjust the timer on my hot water pumps
When I examined my heater closely, I noticed there was a timer in there that wasn't set to do anything. I was hoping this might be for the heater itself, so I could avoid heating my water at all during nighttime hours.

What it actually ended up being was an Aquastat that controls my hot water pumping system. Turns out many apartment complexes have systems that continuously circulate hot water through the pipes so that it arrives more quickly at its destination. You've experienced places that don't have these devices: you have to turn the shower on fifteen minutes before you hop in.

Having the hot water run through all of the pipes continuously cools the water down, especially if the pipes aren't insulated, which mine aren't. Then the hot water heater has to heat that water back up.

I've adjusted my timer to turn off hot water cycling during the hours of 8pm-5:30am. We'll see how this impacts hot water delivery to my bathtub. If it seems to be okay, I might get more aggressive with it.

Implementing this quick change should buy me another 5% energy improvement and CO2 reduction.

3.  Outfit my hot water heater with a jacket
Hot_water_heater_jacket It's pretty cold in my apartment! Our heating/cooling system broke a few months ago, and I've vowed not to get it repaired until I can do so in a more eco-friendly way. It's been a winter heavy with sweatshirts and hot cocoa.

Unfortunately, our hot water heater also lives in our house. This means heating water is more of a struggle for him because he's constantly surrounded by cold. And what do you do to keep in heat? Buy him a jacket, of course.

Hot water heater jackets are relatively cheap, easy to install, and save about 4-9% of your heating energy. Insulating your pipes gives you more bang-for-the-buck in terms of energy savings, but my pipes are all hidden in the walls, so this is a tough project to take on. Taping a jacket around my hot water heater is much more straightforward.

I've ordered a hot water heater jacket from Amazon. It works on natural gas heaters (watch out - some are fire hazards with gas heaters), and costs $36.

4.  Stop using hot water for laundry
If we can keep hot water in the heater, it will stay relatively hot. Using hot water requires that we start the heating process from scratch. There's no way I am giving up my hot baths and showers. But do my clothes and dishes really need the same treatment?

Several sources online state that there is little advantage in this day and age to washing your clothes in hot water. With the exception of grease stains, or things you need to sanitize (baby diapers, sheets infected with dust mites, etc.), everything should get just as clean with cold water. Not only that, but your dyes will bleed less, and your clothes will last longer.

I've been washing our clothes for the last month in exclusively cold water, and have noticed no change. I'm hooked.

What about dishwashing? Because hot water is superior at sanitizing and cutting grease, I plan on continuing to use hot water for washing our dishes.

The end result of the improvements:
All told, these four fixes should improve my hot water heater's efficiency by 25% which is saving around a quarter ton of CO2 a year. Not bad for a few minutes work...

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Don't turn your hot water below 130 degrees....legionaire thrives in 129 degrees. The virus isn't a problem if you take a bath, but is a major problem if you take a shower.....

the post should read 120 degrees instead of 129 degrees...

Interesting. I haven't ever read anything about the risk of legionnaire's disease at lower water temperatures.

I did do a bit of research, and the poster is right. Lower water temps can increase the risk that you might inhale this lung disease via water vapor (probably in your shower).

But research also shows that you'd have to up your water temperature to at least 160 degrees to eliminate risk, and that Legionnaire's can thrive equally well at 140 as it does at 120. Given that 160 is a scalding temperature, I think I'll take my chances and stick with 120 degrees.

Great article! I just followed what you mention here, and my savings have increased! I'm going to email this article to my friends too. Thanks!

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