When to turn off hot water heater?

Is it electric or gas? If gas, just turn the thermostat down to its lowest stetting, but not all the way off. If electric, go ahead and turn off.

My only caveat is if you are in a region that may still get very cold; you don’t want get so cold in your unheated place that the pipes might freeze and then burst.

When water heaters get old it’s best not to mess with them.
related story: I did the same thing 12 years ago but I also inadvertently turned off the power to the fridge in my apartment. When I came back almost two weeks later the fish in the freezer had rotted. Luckily my lease was up and I could just air it out then move out.

You could just turn the temperature down. If you want to bother. If you’re not using the hot water it probably doesn’t cost very much to keep it hot over the two weeks.

I would adjust your air thermostats. In the winter I go as low as 62F when I travel, and in the summer I leave it at 78F, which is the temperature I often have it set at anyway, but a lot if people keep their air conditioner much lower. I think you can easily get significant savings by adjusting the air thermostat.

More importantly you should turn off the main value for your water supply in your house. Not to save money for normal conditions, but to prevent extensive flooding should something go wrong with the plumbing in the house.

I love this Q. There are so many factors that lead to one clear answer:
Just turn off your main water valve and leave the heater alone.

Your heater is in your home. It is mid-March and your heating system will likely need to operate. Every BTU, Watt second, kwHr etc. of heat your tank loses is going into heating your home. You are wasting nothing.
In the summer, when you presumably have A/C on it would be more energy efficient to turn off the hot water heater. as that heat now needs to be removed by the A/C.

But….
There is one overriding factor. Tank life. Typical water tanks have glass linings to hold the water. Glass is very stiff . Thermal and mechanical stress shortens their life. Shutting off the tank heater unnecessarily subjects the tank to 2 full range thermal cycles for virtually no energy saving. The cost and environmental impact of replacing a tank is far higher than any energy saved.

I never turn off the water heater when I travel. The amount of energy it will use is minimal compared to what you normally use while there. If you want to, you can turn down the temp as others have suggested, but that’s not essential.

I do turn off all AC/Heat when I travel. Where I live (Atlanta) the extremes in temperature are not as bad as in the north, so I don’t need to worry about pipes freezing or similar problems. I would answer differently if I were in Maine.

I’ve never thought of turning off the hot water heater and I travel extensively. I turn the regular thermostats down or off depending on the time of year.

Thanks all to the thoughtful answers to this question.

First off, no one uses “hot water heaters”. Water heaters are a thing, but no one in a residential setting uses water reheaters (hot water heaters). We use reheated steam in steam generated power production, but … forget it.

In New England, where most older single-family homes have oil heat, the water is generally heated by the oil furnace in a tankless system. Many times I’ll turn off the furnace daily as I leave the house – and I’ll still have some residual hot water in the evening that I can use to wash dishes. Then I’ll turn on the furnace again in the morning just before I shower. (This isn’t as inconvenient as it sounds, because on homes with a full basement and the furnace downstairs, the shut-off switch is mounted at the top of the stairs.)

I don’t expect any tanks for this response.

Actually @CWOTUS I’m not sure what you’re saying. I definitely have a separate hot water heater and a gas furnace.

@janbb, I thought he was commenting on the redundancy of ”hot water heater” instead of just “water heater.”

^ Indeed.

The water is already hot, no heater is needed.

Just turn it off.

@Jeruba Yes, you may be right but it sounded like he was saying there aren’t separate water heaters in houses. And while redundant, it is what they are called.

@janbb read it again. I didn’t say that there aren’t water heaters in houses; of course there are, and millions of people have them. What I said was that there are no residential hot water heaters, because there would be no need.

Ok – you win.

Ok. Since we’re all being a bit pedantic. I do have a hot water heater. I have an 80 gallon electric and have set the thermostat to kick on at 110 F and off at 130 F. It is in fact heating what some people consider hot water to an even higher temperature.
Why do I do that you might ask? I occasionally hold parties here with many guests and I want there to be sufficient hot water for services By raising the temperature, my hot water consumption is reduced since less is required to so the job. When it comes out of the tap scalding hot people back off immediately. In the shower you only need a little bit to balance the cold.
If I had an oil or gas fired heater I would not have to do this but electrics are slow. There is increase heat loss, of course, but it all goes into my basement which can use the heat anyway.

Thank you, @LuckyGuy, for being the exception to prove the rule.