I don’t need my gas water heater but once every two days. I’m debating whether to use vacation mode. Any thoughts?
Gas or electric? I’ve wondered about this. If it’s well insulated the question is whether it is more energy efficient to heat up a large slug of cold water to temp or, maintain it. I think they are now “smart” enough to factor when demand is highest and kick on a couple hours prior, the flip side of vacation mode.
Can also experiment with lower temps.
What exactly are you trying to accomplish by doing this?
Energy savings will be negligible.
While the controls on a water heater don’t seem to be very cheaply made, they are designed for a light duty cycle, perhaps intended to be adjusted a few times per year. Increasing the duty cycle to 360 times per year may lead to premature failure, though I think this is a minimal concern. Just leave the heater on all of the time is my recommendation.
Does it use any gas on days you don’t use hot water? I’m not sure how to monitor that on a gas hot water heater.
Another option is getting a water heater blanket. My newish energy star hot water heater is about 74F, and the not-running furnace next to it is 71F. That’s a bit of heat loss, but I don’t know if it’s enough to justify spending $30-40 on a blanket.
Obligatory Technology Connections video
That was the recommendation I was looking for.
For what it’s worth, my gas meter reports meter readings to the utility company on an hourly basis, and their website shows this level of granularity. For days when the house is vacant, and the only use is the water heater holding the temperature constant, my gas usage is 2 cubic feet (CF) of gas per day, with no adjustment from the regular temperature setting. That’s quite low compared to my average use of 35 CF of gas per day.
There’s another kind of water heater called a “tankless water heater” that might be useful for this kind of scenario. It’s a heater where cold water is routed through pipes that are heated just when you need hot water. It’s like using a blow torch to heat up the water pipes, but it’s only on when the hot water tap is turned on. Otherwise, the system sits dormant not using any energy. It wouldn’t be worth switching since it’s expensive to install, but you might consider it in the future if you’re having to replace your water heater.
I don’t think that switching it to vacation mode on a regular basis will produce enough savings to make it worth the effort. But it would be an interesting experiment to try. You could try it for a month or two and see how it changes your bill.
One concern I would have is that that the larger temperature swings would mean the tank would expand and contract more often and to a greater degree. If your tank is always at Hot temperature, then the tank housing will stay expanded according to that temperature. But if your tank keeps alternating between Hot and Vacation temperatures, it will be continually expanding and contracting. That could lead to more cracks and early failure.
If my gas use of 2 CF per day to keep an idling water heater is correct, and assuming 1050 BTUs per CF and my 80% efficient water heater (50 gallon, factory insulation only) that’s 1680 BTUs used per day. Electric equivalent is 0.492359345 KW Hr.
Electricity costs vary, but I pay 13 cents per KW Hr, so that would save 6.4 cents per day, or 96 cents per month if I had it off for 15 days per month.
I converted to electric equivalent simply because I know my cost per KW Hr off the top of my head. I would have to go digging for my gas cost per dekatherm, and I don’t have the time to do that, but generally I think gas is lower cost than electric in most cases. Of course overall cost including service charges would change the numbers, but I have better things to do than save 6 cents every other day.
My 2020 80% efficient gas Rheem (so nothing fancy) is already fully self-insulated. As was my previous water heater from sometime around late 1990s or early 2000’s. So blankets seemingly aren’t typically indicated anymore.
Just a warning, depending on the age of your house this may not be feasible due to gas flow rate - the on-demand heaters use a high volume of gas for a short time. We looked into adding an on-demand heater when we had to replace our heater a few years ago, and it turned out we would have needed to run a new gas line from the street to the house at a prohibitive cost.