Can I leave my tankless water heater on all the time?

Author: Ethan Murray  |  Last update: Saturday, January 3, 2026

Yes, you can leave your tankless water heater on all the time. The system only heats water as it is requested, so there's no unnecessary energy consumption. For vacation properties, it's still recommended to leave the unit on, but if you choose to turn it off, ensure you drain the system entirely to prevent any damage.

Should I turn off my tankless water heater when not in use?

I personally would only turn it off if leaving for more than a few days. Also, if you're gone for a week or more with the water heater off, it's always a good idea to turn the temp up to max and run a tank through it before turning back down to your desired temp (caution it'll be hot as fuck).

Can you run a tankless water heater continuously?

Unlike traditional water heaters that continuously heat and reheat water in a large tank, tankless models provide hot water on demand, heating water directly as it flows through the device. This innovative approach not only conserves energy but also offers the allure of never running out of hot water.

Can a tankless water heater overheat?

A restriction in the air supply or venting system can cause overheating. Flue gases are hot. If something blocks the exhaust, the hot gases might overwhelm and overheat the system. If something blocks air supply, the burner might run hotter than usual and overheat the system.

Is it okay to keep the water heater on all the time?

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.

Why Is My Tankless Water Heater Turning Off?

What happens if you leave a water heater on all day?

prolonged usage may cause the geyser's heating element to overheat, potentially damaging the appliance. This was the main reason why the appliance burst. Other things that can happen are: Continuous operation results in unnecessary energy consumption, contributing to higher utility bills.

Is it better to keep hot water on constant or timed?

Although it takes longer and requires more fuel to heat cold water, the energy required to maintain this constant temperature is much more expensive than the few times it is heated when necessary on occasion, due to its non-use, this water is also wasted, as a result, running a boiler continuously consumes more fuel ...

What is the downfall to a tankless water heater?

A tankless water heater cannot provide hot water faster than its ability to heat the water. While a tank unit can provide hot water for multiple uses at once, a tankless unit might not be able to support simultaneous usage, such as washing dishes, taking a shower and running a washing machine all at once.

Why does my shower get cold with a tankless water heater?

Low water pressure can affect the performance of a tankless water heater. A plumbing crossover can cause low water pressure by connecting the cold and hot water lines incorrectly. Installing a pressure regulator can help regulate water pressure and ensure a consistent flow of hot water to the tankless water heater.

Do tankless water heaters need to be flushed every year?

Over time, a tankless water heater may accumulate mineral build up which can erode the walls inside your tank's heating chamber. To properly maintain and clean your tankless water heater, it's important to flush those mineral deposits at least once a year.

Why avoid a tankless water heater?

Additional Installation Costs

Tankless water heaters are much more complex than traditional hot water tanks. As a result, they require professional installation. If you're switching from a hot water tank to a tankless unit, you will likely need your gas lines rerouted, as well as a larger gas supply line.

What is the lifespan of a tankless water heater?

Tankless water heaters usually last for around 15-20 years before they need to be replaced, but they may need replacing sooner if they start to break down or lose efficiency. Some common signs your tankless water heater needs to be replaced include: Low water pressure. Water doesn't get hot.

Can I replace my 40 gallon water heater with a tankless water heater?

Absolutely! In fact, tankless water heaters are becoming the standard for new home construction because of the energy efficiency.

Can you leave a tankless water heater on all the time?

Yes, you can leave your tankless water heater on all the time. The system only heats water as it is requested, so there's no unnecessary energy consumption. For vacation properties, it's still recommended to leave the unit on, but if you choose to turn it off, ensure you drain the system entirely to prevent any damage.

Can a tankless water heater run constantly?

Tankless water heaters are both convenient and efficient, but they can begin to function erratically from time to time. They are designed to run constantly, supplying a constant flow of hot water. However, like any other electric appliance, it is susceptible to damage.

Why don t more people use tankless water heaters?

Some people hesitate to decide on a tankless water heater because they can be a slightly higher cost; however, you get significantly more life out of one. A standard water heater tank lasts about 8-12 years. A tankless water heater can last as long as 25 years!

Can you run the dishwasher and shower with a tankless water heater?

With a tankless water heater, you can take a shower, use the dishwasher, and do laundry all at the same time without losing hot water. On top of saving, you from the dreaded cold shower, it can also save you money and energy.

How do I protect my tankless water heater from the cold?

Installing a tankless water heater cover for winter is another option; it will protect the unit from the coldest temperatures, not to mention snow and ice. Run a Faucet on Low: Water is more likely to freeze when not in motion. To reduce the risk of freezing, run a faucet at a low level during extreme cold.

What maintenance does a tankless water heater need?

The most complicated and time-consuming tankless water heater maintenance is typically descaling and flushing out the unit. Even with the inline water filter, lime and calcium deposits can build up inside the tankless system. If you have hard water, it's a good idea to descale and flush the unit once a year.

What is negative about a tankless water heater?

Unlike traditional storage water heaters, tankless units may not be able to meet your home's hot water needs if you have multiple outlets running simultaneously. This is because the flow rate of a tankless unit may not be high enough to support multiple uses of hot water at the same time.

Do tankless water heaters increase water bill?

Because tankless water heaters only consume energy when you need hot water, they're more energy efficient, saving you money on water and energy bills.

How much money will I save by switching to a tankless water heater?

It's true: tankless water heaters will cut up to 40% off your monthly energy bill. By heating water instantaneously and only when you need it, you and your family members can enjoy continuous, uninterrupted hot water at the same time, along with savings over a conventional tank.

Is it okay to leave the water heater on all the time?

Generally speaking, a gas water heater should not be turned off unless you are leaving the house for an extended period of time. Even then the better choice for gas water heaters is to just turn the temperature down. In fact, many water heaters have a “vacation” setting on the temperature control.

What is a good hot water schedule?

Try heating the water for an hour in the morning and an hour in the evening.

Why do I only get 10 minutes of hot water?

If your hot water runs out too fast, you may have an issue with: Too much hot water demand from multiple sources at the same time. Sediment build up inside of your water heater tank. A broken dip tube.

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