How Much Electricity Does a Tankless Water Heater Use

Heating water can be one of the largest expenses as it consumes a large amount of electrical power. According to the Department of Energy research, water heaters are the most demanding appliances and consume nearly 17 to 24 percent of the home’s total utility cost.

But surprisingly, tankless water heaters are very economical and easily last up to a decade. They reduce the amount of the bill and are very efficient compared to the traditional water heaters.

Many factors, including the size, model, and temperature, add to the cost and electricity consumption. They have many benefits and are better options in power and consumption.

A detailed discussion related to the question of How Much Electricity Does a Tankless Water Heater Use is discussed in the article below. Daily and monthly estimates are also mentioned that help you draw an idea about these efficient appliances.

How Much Electricity Does A Tankless Water Heater Use?

Working Mechanism

Tankless heaters are also known as the demand heaters as they lack a tank like the traditional water heaters. They do not store gallons of water and heat that continuously until someone needs it. Tankless heaters heat the water when the consumer generates the demand.

When the tap is on, the water starts getting heated. This is the main difference between traditional and tankless water heaters. Tankless water heaters save you from waiting for long hours until the tank refills.

You go for a shower and turn the tap on. The hot water starts flowing from the pipes until you stay in. An electric heater is present that heats and delivers a constant water supply no matter the time. The only concern is the water flow if the tap is on for a long time.

The tankless water heater limits the flow and provides water at 2 to 5 gallons a minute. This flow even decreases if hot water is being used at two different places simultaneously.

A solution for increasing the water flow rate is to install multiple tankless heaters in the home. Make a connecting point of the water from all these heaters to deliver a high flow rate even if used at various places around the house. Washing clothes and taking a shower at the same time will not be a problem.

Electricity Consumption

Heating water is a power-hungry process as it requires a huge amount of electricity. Tankless water heaters heat the icy cold water in 20 seconds at the most. They work efficiently and use a tremendous amount of power for performing heating tasks.

But let’s compare the electricity consumption by a tankless water heater to the other appliances present in our homes. They are much more economical, keeping in mind that they work when the demand is met.

For example, an average washing machine that works for 2 hours will use almost 1000 kW more electricity to get the work done. Many consumers also observed that using tankless water heaters has resulted in reduced electricity bills.

To prove this, research was also conducted by the US Department of Energy, which stated that tankless heaters are 24 to 34 percent more efficient. Households that use 41 gallons of water on average are saving money by using these efficient appliances.

Average Cost Per Hour

The calculation of the electricity consumption of the tankless heaters is straightforward. You only need to calculate the watts used by the heater, and it can also vary for different models. According to the US, we will consider the average price of $0.1319 per kWh as a standard.

If the tankless water heater consumes 20 kWh, the average cost will be $2.62 per hour. Many factors like temperature required for heating, time, output, and model will also add up or reduce costs.

This calculation is done if the tankless water heater gives 100 percent output which is very unlikely as the output decreases with time and which, as a result, reduces the cost as well.

The heater will provide 100 percent output in the first 15 minutes only. This is a straightforward process that results when we calculate the product of the watts used and the electricity cost.

Different models are available in the market and use different kilowatts per hour—the consumption changes according to the model we are using.

For example, using the tankless water heater that uses 10 kWh will use $1.32 per hour. This calculation is only accurate if the heater gives 100 percent output which is very unlikely if used for a long time.

Average Cost Per Month

It isn’t easy to calculate the cost of electricity used by the tankless water heater daily. A monthly record and the bill at the end of the month will reveal these heaters’ actual performance and cost. Calculating the exact number of hours daily with 100 percent output can be a time-consuming and hassling process. So we take rough estimates of the time, output according to the number of people living in the house.

A family with 4 to 5 people will use 20 to 60 gallons of water on average in a day. The water flowing for the first 35 to 40 minutes will only have 100 percent heating output.

This level will decrease to 97 percent, which is the average estimate made by the experts. Taking $0.1319 per kWh as the standard as we took above, the average cost of electricity used by the 20 kWh tankless water heater will be $46.20.

We can calculate the amount of electricity used by these heaters for a year by using this figure. A total of $554.40 is used in an entire year if you use the demand heaters.

Hence this amount is far less than the water heaters with a storage tank. Electricity or gas is used to keep the water boiling until it is used. This adds up to the cost and wastes resources.

Measures to Minimize the Bills

We are well aware that tankless water heaters are efficient and economical appliances, but they are some measures that can be observed to minimize the bills further. Follow these tips while using the tankless water heater and will notice a decrease in the bill for the next month.

  • Thermostat: People use tankless water heaters at high degrees as they lack water storage tanks. This does not affect the temperature of the water as it delivers when hot water is demanded. Keeping the temperature at 120 degrees would be enough to provide hot water.
  • Shower Time: The tankless water heaters work only when the tap is on. The bathing time and water consumption will affect the bills. Closing the tap while you shampoo the hair or soap up will reduce the consumption time and restore the water flow.
  • Efficient Model: Different models are present in the market with different electricity consumption. The models having the latest technology have Energy Star Labels. They use less electricity and provide a heating output of 99 percent, which is pretty impressive. This will help you save a lot of money in the long run and is considered an investment.
  • Dishwasher/Washing Machine: If you wash the dishes by hand, you will use more water than a dishwasher. If you have a tankless water heater in your home, investing in a good dishwashing machine that consumes less water for cleaning the dishes is recommended. Similarly, an efficient washing machine should get the work done quickly.


Do tankless water heaters increase electric bills?

No, the tankless water heaters do not increase the electricity bill. They are efficient and economic appliances used only when there is a demand for hot water. These heaters do not waste resources and save money.

What is the downside of an electric tankless heater?

The only downside of the electric tankless heater is the high purchasing cost. They provide instant hot water when demand is made and save a lot of time. This should be considered an investment that will benefit in the long run.

Can a tankless water heater fill a tub?

Yes, a tankless water heater will fill the tub for you. It lacks a water storage tank and delivers a constant hot water supply without running out. You can quickly fill the tub and enjoy a hot bath.

Can a tankless water heater work for the whole house?

Yes, the tankless water heater can work for the whole house and meets all the hot water demands. They are efficient and have high temperatures to deliver a constant supply of water built to serve simultaneously.


The tankless water heaters use less electricity than the traditional heaters and save a lot of money. These lack the storage tank that uses resources even if no one in the house is using the hot water.

Hence they are more efficient and can easily last for more than a decade. The water flow might be slow, but this can be solved by using two or three units together with a connection point. It has many benefits and is considered a wise investment.


Read Also:

With years of experience under his belt, Adam decided to put his water heater knowledge to work. By providing high-quality content and expert guides, Adam hopes to help anyone looking for expert water heater advice.