Turning off a tank water heater entirely during the day only saves a few dollars a month. Because it takes a massive amount of energy to reheat an entire tank of cold water, shutting it off daily is largely ineffective and often inconvenient.
The energy experts say it's about $1.36 a day. The question you have to answer is whether it's worth it because there are some inherent problems with turning a water heater on and off. No hot water when you return. Lukewarm water doesn't really do anyone any good.
If you're not sure how long it takes, try turning the heating on about 30 minutes before you need it. You should turn it off 30 minutes before you'll stop needing it. You might need to turn on your heating earlier if your home takes longer to reach a comfortable temperature.
It's better to leave the hot water heater on all the time, rather than turning it on and off. This is a very common energy saving myth. But in fact, you really don't need to be heating your water all the time. Your immersion heater or boiler will heat up hot water which is stored in a tank.
If your model has a built-in timer or is connected to a smart home system, set it to heat water early in the morning or overnight. That way, you've got hot water when you need it, without heating during the most expensive hours.
Some common causes of high water bills include:
Showers & Bathtubs
The average shower uses about 2 gallons of water per minute. If there are four people in your household and each person takes a 10-minute shower daily, that's 80 gallons of water.
Only heat the hot water twice a day
Try heating the water for an hour in the morning and an hour in the evening. Start the water heating about an hour before you need it. For example, if you shower at 08:30, start heating the water at 07:30. If you wash up in the evening at 19:30, then start the water heating at 18:30.
If the main water supply is off, the tank might run dry. If the heater keeps running without water, the burner can overheat and damage the unit. This can lead to expensive repairs or warrant a complete water heater replacement.
Water heating is the second largest energy expense in your home, accounting for about 18% of your utility bill. To conserve hot water, you can fix leaks, install low-flow fixtures, insulate accessible hot water lines, and purchase an ENERGY STAR certified dishwasher and clothes washer.
Here are the most significant home electricity users:
Inadequate or inconsistent insulation, like air leaks, can create hot and cold spots throughout your house. If you've ever seen any of your home's insulation, it's probably what resides in your attic or crawl space.
Heating and energy expert Stephen Hankinson said that one "big energy cost saver" is to make sure you have your heating off when you're not at home. For instance, if you typically arrive home from work at around 6pm on weekdays, you could set your heating to activate just as you walk through the door.
Shutting Off Your Water Heater Can Cause Problems
If you have an older unit, you may have some difficulty turning it back on after being shut off for several days. The stress of rebooting the system of an older unit could lead to water heater repairs or a full replacement.
OVERALL COST
Savings resulting from turning down your water heater temperature are based on reducing standby losses (heat lost from water heater into surrounding area). Set too high, or at 140ºF, your water heater can waste anywhere from $36 to $61 annually in standby heat losses.
If you keep your water at a high temperature all the time, you will lose more heat to the environment even if the cylinder is well insulated. Your water heating costs will increase in direct proportion to the average temperature of the cylinder over the day. You will end up paying for more energy as a result.
Electric tank water heaters hold hot water in a large insulated tank. In the event of a power outage: The preheated water remains hot for 1–2 hours if not used. If the tank is well-insulated and full, it can hold usable hot water for 6–12 hours, depending on ambient temperature and demand.
So, should you turn off the water heater when your water is off? Absolutely; leaving it running during an outage means: Overheating risks: The heater elements or burners keep heating with no water to absorb the energy. Pressure issues: Valves may become stressed, leading to leaks.
Over time, the constant operation can cause wear and tear on the heating element and other components. Additionally, the risks of geyser overheating become more pronounced, potentially causing damage to internal parts and impacting the overall lifespan of your appliance.
The average shower water usage is calculated by multiplying that average flow rate of 2.1 gallons per minute by the average shower length of 8.2 minutes. So, 17.2 gallons is, on average, how much water is used. In a 10-minute shower, you'll go through 21 gallons. Water used in the shower can add up.
NHS advice is to 'heat your home to a temperature that's comfortable for you', which should be 'at least 18°C in the rooms you regularly use, such as your living room and bedroom. ' 14 degrees is not a healthy room temperature.
This makes it possible to adjust the water heater temperature to optimize energy consumption. For most homes, a domestic hot water temperature around 45-50 °C during summer is more than sufficient. This ensures the water is adequately hot for daily needs without wasting energy through overheating.
To help us save every drop of water, showers should be kept to four minutes or less. Wondering if cutting a couple of minutes off your shower really helps? The answer is yes!
Toilet and faucet leaks
The most common cause for a high water bill is running water from your toilet. A continuously running toilet can waste up to 200 gallons a day or more depending on the volume flow down the drain.
Electric showers typically use between 8.5 and 10.5kW per hour. At the current UK average electricity price of 24.5p per kWh (as of April 2025), a 10-minute daily shower could cost approximately £0.43 per use — that's around £157 per year for one person.