Hot Water Heater Audit

Up until recently, my energy audits have pretty much ignored my appliances. Which is an enormous thing to handwave. Appliances are huge energy suckers. But my arm muscles are too measly to roll them out of their designated areas to leverage my Kill-A-Watt. And most of them are sufficiently old that there is no published energy information about them.

My hot water heater, however, has its energy information posted right on its side. I have a natural gas hot water heater, which is pretty common. Over 2/3 of American households heat their home or water with  natural gas. Generally, hot water heaters are the #2 energy users in the home, after the home heating system. Let's take a look at my water heater:

Here it is. I have to say that I have no complaints about it. My water is always nice and hot. But boy, does it look complicated. Tons of tubing and dials and boxes and meters.

Two things stick out: there seems to be some sort of timer in the upper right hand corner. Inspecting it further, it appears to be set to the "off" position from 1-2am and then "on" the rest of the time. I have no idea what this is for, but it excites me. Where there's an off switch or a timer, there's usually an opportunity to save some energy!

The other knob towards the bottom clearly controls the hot water temperature. It seems to be pushed a little past its recommended setting. Which could mean I'm overheating the water.

Trouble is, I have no idea how much natural gas I use. In our condominium complex, natural gas is split up and divided equally amongst all of the units. Now that I think about it, it's hardly fair. No matter how much I am able to reduce my natural gas consumption, I won't save any money.

I can however, endeavor to reduce my carbon emissions. Natural gas, while much better than its fossil fuel cousins, still releases CO2 and other gases when it burns.

Let's see if we can come up with an estimate of how much CO2 is released from this guy per year. Warning: math ahead!

The number on the Energy Star tag tells me that this hot water heater uses 272 therms/year. A wikipedia search reveals that a therm is a heat unit equal to 100,000 BTUs, another heat unit.

Searching on natural gas reveals that 1 cubic foot of natural gas can produce about 1030 BTUs, but most natural gas hot water heaters are only about 90% efficient in acheiving this metric. Okay, now we're getting somewhere. 1 cubic foot of natural gas yields about 927 BTUs in my hot water heater.

That means that there is over 29,000 cubic feet of natural gas pumping through my pipes to that water heater every year. Every twelve days I've burned through enough natural gas to fill up my entire apartment!

It's a lot, but it's nowhere near what I'm being billed for. The $7/month that I pay should get me 84,000 cubic feet a year.

Now we need some way to translate this into CO2 levels. Naturalgas.org states that 117,000 pounds of CO2 go into the air for every billion BTUs of natural gas burned. Big numbers, but it should work. That's 117 pounds for every million BTUs.

Crunching the numbers tells me that 272 therms is equal to 3182.4 pounds of carbon dioxide. Unbelievable. Just heating my water produces 1.5 tons of CO2 a year. I'd need to nurse 38 saplings from infancy to ten years old to soak up that much carbon.

There's a shortcut through this formula: X therms * 12.0593 = pounds of CO2 emitted. Try it yourself and see how much CO2 you're producing.

I'm off to investigate how to reduce this.

Comments

[Crunchy Chicken]

You can start by turning your water heater down to 120°F (any cooler than that and you risk not killing off bacteria). For every 10°F that you turn the temperature down, you will save 4% on the water-heating portion of your utility bill.

I didn't see an insulating blanket, so adding one would help reduce the energy required to keep the water hot.

Since you have natural gas, another option, if you wanted to replace it (really only recommended if it's older than 12 years or is very inefficient), is a tankless water heater that heats on demand. They reduce energy consumption 20 to 30 percent. And with no storage tank, standby loss is completely eliminated. (I haven't seen much energy benefit on the electric tankless ones, only the natural gas powered ones.)

Finally, use less hot water. Don't let the water run when you are not using it, install water-saver showerheads, take shorter showers, etc.

[Tony]

I recommend this easy and inexpensive solution to saving water, time, and energy; install a Hot Water Lobster instant hot water valve under the sink farthest form your water heater and you will have instant hot water throughout your entire home. It saves a lot of water that's normally wasted down the drain while waiting for hot water. The savings in water and energy easily recoups the initial $179.95 purchase price! More impressive is the convenience of instant hot water!

The Hot Water Lobster uses no electricity and is pump free, so it creates no noise. It is made in the U.S.A., has a 10-year warranty, and can be easily installed in under 10 minutes.

Check it out at:
www.hotwaterlobster.com

[plumbing claremont]

I also have no idea how much natural gas I use. In our house, natural gas is split up and divided equally amongst all of the units. Now that I think about it, it's hardly fair,you have a nice blog.

by: jb