how much electricity does a tankless water heater use

How Much Electricity Does a Tankless Water Heater Use?

Ian Mutuli
Updated on
Ian Mutuli

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
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Tankless water heaters have been around most residential homes for a while now. While you might enjoy the perks of instant hot water, tankless water heaters are some of the most energy-hungry home appliances. So it’s essential to know just how much power they use. But how much electricity does a tankless water heater use? Read along to find out.

What is a Tankless Water Heater?

Tankless water heaters, otherwise known as instantaneous water heaters, only provide hot water as needed. Additionally, tankless water heaters don’t come with the standby energy losses like most traditional tank heaters. These systems use an on-demand technique to heat water instead of repeatedly maintaining the heat intensity of an entire tank of water.

What is a tankless water heater?

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A tankless water heater doesn’t need to work constantly, and there’s no limit to how much-heated water you can use at a time. You don’t have to worry about running out of water mid-shower. Not to mention, tankless water heaters are the most efficient models. Having a tankless water heater to replace your old hot water system is the best investment you could make.

How Much Electricity Does a Tankless Water Heater Use?

To give a rough estimate of the electric consumption of a tankless heater, we have to consider a few things. Remember, they only have to be active for a short amount of time, which means they rarely run at full capacity, depending on the size of the unit and the amount of hot water used. You also have to factor in that you have to choose between an electric or gas tankless water heater.

How much electricity does a tankless water heater use?

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A mid-size home will require a tankless water heater with a minimum heating capacity of 18kW. This means it can serve 4 people without a problem. Therefore, a tankless heater might draw 18 kW for the first 30 seconds and less energy as it continues to operate. A family of 4 requires at least 50 gallons of water, and using a tankless solution will only use 1kw a day. In most areas, 1kw of electricity costs 15 cents.

Therefore, you can expect to spend roughly 9 kWh or $1.35 of electricity per day. For your monthly expenditure, you would use roughly $40 and $493 every year. Keep in mind; these are rough estimates since the real electric bill is dependent on how many outlets you have in your home, your water consumption habits, where you live (apartment, townhome, or condo), and your local climate (you’ll consume more electricity in cold climates compared to hot ones). Furthermore, the price of electricity varies between states.

Let’s assume that you use hot water for house chores and not just showering. Here are the estimations if you choose to continue with an 18kW heater. If you need to handwash dishes, assuming the heater will be on for 5 minutes and at medium capacity, your heater will use 1.2kW.

Why Do Electric Tankless Heaters Need Such High KW?

Given the energy-saving factor you must consider, it might seem counterproductive that an on-demand water heater might have higher KW requirements. However, a tankless electric water heater can heat a large amount of water quickly. Additionally, a large tankless water heater can draw 36kW when heating water.

Why does an electric tankless water heater needs a high kW?

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To reiterate, tankless heaters only need to deploy power for a matter of seconds (mostly under 10), compared to most hot water appliances in the home, including traditional tank heaters, which run for hours at a time since they have to keep the water warm and ready for use.

While electric tankless water heaters spend a lot of electricity during a short period, after you turn on the shower or a tap faucet, they work quickly and sit in rest mode the rest of the time. This can lead to a reduced energy costs by at least 40%.

How Does a Tankless Water Heater Work?

Tankless water heaters usually use either electricity or gas to heat cold water immediately after it enters the unit. If it’s a gas tankless water heater, it works by heating water using a gas burner. On the other hand, if it’s an electric water heater, it works using electrical resistance heating coils. For any tankless hot water heater, this means it gives two to five gallons per minute.

How does a tankless water heater work?

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Gas-fired tankless water heaters have elevated flow rates compared to electric ones. However, even the largest gas tankless water heater might not be able to cope with too much. For instance, multiple uses (running a dishwasher and shower) simultaneously might defeat the purpose of energy savings, depending on electricity usage.

Factors to Consider Before Getting a Tankless Water Heater Installed

1) Look For a Self-Cleaning Function

A self-cleaning feature is a feature that can guarantee energy efficiency. It keeps the heating elements clean, which in turn keeps it energy efficient, and improves its performance. This will use less energy and save money while keeping your energy consumption bearable. A self-cleaning function not only saves energy, it also extends your tankless water heater’s life since it prevents the build-up of deposits.

Look for self-cleaning function

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Self-cleaning tankless water heaters have a curved dip tube that circulates the water to prevent sediment from settling at the bottom of any heating elements. Additionally, the sediment is flushed out of the hot water supply pipes and significantly decreases the chances that your tankless water heater will overheat.

2) Energy Star Rating

As previously stated, heaters with an Energy Star certification are more energy efficient than those without one. In this way, assuming you’re searching for an energy-proficient tankless water radiator, pick a water heater type with an Energy Star rating. Therefore, you should rest assured that you’re getting a great, energy-saving item.

Energy star rating

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Besides being increasingly energy-efficient, Energy Star-certified heaters also have other advantages. For example, they often include some qualities that make them more durable and easier to use. Of course, since they’re more efficient, they create just the required heat without any wasted energy.

3) Recirculation Pump

recirculation pump circulates the water through the heater at intervals. Therefore, the water in your pipes never cools off, so you have water readily available whenever you need to wash the dishes or shower. The pump is convenient, so you no longer have to wait for warm water in the morning before you shower.

Recirculation pump

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Additionally, when you turn off a tap or fixture, a recirculation pump pushes any hot water that’s left, back into the tankless water heater. Apart from reducing water waste, a pump can help the water to be heated again, so you have no cold water running out of your hot water fixtures.

Frequently Asked Questions About How Much Electricity a Tankless Water Heater Uses

i) Do tankless water heaters use a lot of energy?

Yes, they do. Tankless water heaters are usually powered by electricity or gas. However, despite using a lot of energy, these water heaters were at least 22 percent more energy efficient on average compared to most gas-powered storage-tank models.

ii) Do tankless water heaters cost more to run?

The initial cost of a tankless water heater is more substantial compared to that of a conventional storage water heater, but they will usually last you for long and have lower operational and energy costs, which could balance out their higher purchase price.

iii) Are tankless water heaters economical?

The U.S. Department of Energy reports that a tankless water heater is at least 24% to 34% more energy-efficient than storage tank type water heaters—assuming that you use about 41 gallons on a daily basis. However, even if you double that amount in a day, they are still about 8% to 14% more efficient.

iv) Is it worth it to switch to a tankless water heater?

Yes, it is. An electric tankless water heater can save you money on your energy bill at the end of they day, but they also require a greater preliminary financial investment upfront. Installation costs more, especially if your first tankless heater requires new gas lines and venting or a dedicated electrical circuit.

The Bottom Line

A tankless water heater is a workhorse that runs every day through every season, to deliver hot water to showers and sinks all around your home. They are also a great option if you don’t have space for a conventional tank or don’t need much hot water.

Ian Mutuli

About the author

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
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