# Should I insulate my water heater?

I figure it would be a good idea. It’s an ordinary electric household water heater, half the normal size. It fits under a counter.

Should I just wrap a bunch of pink toxic stuff around it, or what?

They usually have plenty of insulation inside. Is yours putting off an appreciable amount of heat into the room?

Hmm… now that you ask, no, it isn’t. It’s slightly warm in spots, but that’s it.

Insulating a water heater will help keep the water from cooling off as much as normal, thus keeping the heater from cycling on as much. This will allow the heater to use less energy. The difference may not be enough to see on your monthly bill but it will be there.

When I bought one I asked the store that myself, he said they were already insulated inside.,

Water heaters are insulated, but adding MORE insulation lets them use less energy to maintain the temperature of the water. The current issue of Consumer Reports recomends adding insulation to water heaters and insulating the hot water pipes to save energy and save water (the water in the pipes won’t cool off as much so the water at the tap will warm up faster, you won’t have to let the water run to get hot water all the way from the heater to the faucet).

Hmm… insulate the pipes, ey? I just gotta insulate something, I just gotta. Thanks for the responses, and thanks in advance if there are any more!

I would insulate if the outside of the WH feels warm.

It is possible to overinsulate! The equation for heat transfer out of a cylinder shows heat loss being based off of thickness of insulation but also radius^2. As you add insulation, the extra insulation slows the rate of heat Xfer, but the increased diameter (and therfore heat loss surface) increases. At normal thicknesses, extra insulation slows heat xfer, but since the factor is r^2, at some point it “catches up” with the extra insulation, after which more insulation will actually make the thing less efficient.

I haven’t done the calculation, but I suspect you’d need a shitload of insulation to get to that point.

If you can’t feel a warm exterior, it may not be worth the insulation. But doing the pipes is a good idea.

also throw a little insulation on the inlet pipe - maybe a foot or so

Also, make sure that the P&T valve isn’t obstructed. This is the pressure relief valve for the heater; it keeps the heater from exploding if the pressure gets too great inside (admittedly, it rarely happens, but you can’t be too safe.)

If this was a gas water heater, you would also have to keep the insulation away from the inlet and the exhaust flue.

it is a good idea, saves you some money for very little cost. many stores sell a blanket of insulation, made especially to fit around water heaters, almost like a coat.

Also most manufactures say don’t insulate the H.W.H. and it will void the warnentee if you do.

also I think cornflakes ment the air intake when he said the inlet - the inlet water pipe should get a little or else it acts like a cooling fin for the tank

don’t obstruct the overpressure valve

Insulation is so cheap anyways, you may as well if you can feel any warmth at all.

Sounds like a plan but I don’t have any room to put a blankie on it. It sits right here in my
living room, so any heat coming from it warms the house

Right.

so any heat coming from it warms the house

then the only time it will help you (to insulate) is in the summer if you have a/c in that area. Also it will help a little if you use lets say an electric hot water heater and oil furnace since oil is cheaper.

So lets get the details:
what fuel is you hot water heater? - you said electric
what fuel do you use to heat you home?
do you air condition your living room in the summer?
if not does it give off ‘too’ much heat in the summer?
does it give off too much heat in the winter?
if the waste heat is actually used to heat the room then it’s not lost.

These water heaters are tested by UL when used as the manufacturer instructed. If the manufacturer says not to insulate, DO NOT INSULATE.

Part of the certification process involves verifying that wiring and other electrical insulation is not over heated. Adding insulation to the outside of the heater creates the risk of burning insulation off wiring internally and possibly starting a fire or creating a risk of electric shock. Or less dramatic would be buring open the thermal protective device that would permanently disable the heater.

Trust the manufacturer, they would not bother printing the instruction not to insulate unless they had a real reason.

From the Department of Energy:

Looks like insulating the water heater is a good bet.