Closeup on the bottom of a water heater as a homeowner adjusts the temperature

Are you in the market for a tankless water heater? If so, you may have heard that these appliances heat water on demand, meaning they only use energy when hot water is needed. 

But, how much energy does a tankless hot water heater actually use?

This post will explain some factors that affect energy consumption for tankless water heaters and provide tips for choosing an energy-efficient model.

How Much Energy Does a Tankless Water Heater Use?

On average, tankless hot water heaters use 6.76-9.80 therms/month (about 198-287 kWh/month). That’s about 24-34% less energy than a comparable storage tank water heater. Therefore, tankless water heaters can save you money on your energy bill each month.

Tankless Water Heater Energy Consumption Variables

As mentioned, a tankless water heater uses about 24-34% less energy than a storage tank heater. However, several factors can affect a tankless heater’s energy consumption. 

Some of the most critical variables include:

Energy Consumption Rises With the Number of Rooms

The number of rooms in a home is one of the main factors affecting a tankless water heater’s energy consumption. If you have many rooms, you’ll need more hot water, and your heater will use more energy.

According to The National Renewable Energy Laboratory, a standard tankless heater in a one-bedroom house uses up to 9.8 therms (287 kWh) in January. In a three-bedroom home, the consumption rises to 11.76 therms (about 345 kWh). And in a five-bedroom house, the heater will use 15.67 therms ( 462 kWh).

As you can see, the number of bedrooms in your home significantly impacts your heater’s energy consumption. So if you’re looking to save energy, it’s best to choose a smaller unit for a one or two-bedroom house and a larger unit for a three or four-bedroom dwelling.

A tankless water heater installed on a wall

More Family Members Means More Energy Consumption

Not only does the number of rooms affect your heater’s energy consumption, but also amount of people in your home. The more people there are in your household, the more hot water you’ll likely use daily. As a result, you’ll need a heater with a higher capacity to meet your hot water needs.

Energy Consumption Is Higher in Colder Months

Another factor that affects your tankless water heater’s energy consumption is the weather. In general, your heater will use more energy in colder months, as it will have to work harder to heat the water.

Cold water requires more energy to heat up than warm water. As a result, your heater will use more fuel in winter than in summer. 

The Right Size Water Heater Can Save You Money

The size of your tankless water heater is another crucial factor to consider.

If you choose a unit that’s too small, it won’t be able to meet your hot water needs, and you’ll end up using more energy. On the other hand, if you choose a unit that’s too large, it will use more energy than necessary. 

Therefore, choosing the right size heater for your needs is essential.

Energy Star-Certified Heaters Are More Efficient

Energy Star Certified tankless water heaters are generally more energy-efficient than non-certified models. Energy Star is a voluntary program that helps consumers save money and protect the environment by choosing energy-efficient products. 

To be certified by Energy Star, a product must meet strict energy efficiency guidelines. That includes tankless water heaters, which must have a Uniform Energy Factor (UEF) of 0.87 or higher.

A picture of five appliances with the energy star logo above them.
Energy Star certifies all types of home appliances, not just water heaters.

In simple terms, the UEF measures how much hot water the heater produces per unit of fuel consumed. The higher the UEF, the more efficient the heater. For example, a heater with a UEF of 0.87 will use less energy than a heater with a UEF of 0.80 to produce the same hot water.

Note: The UEF requirement for tankless water heaters may change in the future. For the most up-to-date information, check Energy Star’s website.

Tips for Choosing an Energy-Efficient Heater

Now that you know the main factors that affect a heater’s energy consumption, here are some tips to help you choose an energy-efficient model:

Choose a Heater With a UEF of 0.95 or Higher

When choosing a heater, the most crucial consideration is energy efficiency. The UEF, or Energy Factor, is the best way to compare the energy efficiency of different models. Look for a heater with a UEF of 0.95 or higher. That means that the heater will use less energy to produce the same amount of heat, resulting in lower energy bills and a smaller carbon footprint.

In addition, a more efficient heater will also generate less heat waste, making it easier to maintain a comfortable temperature in your home. So when you’re shopping for a new heater, be sure to choose one with a high UEF rating.

Get a Heater With an Energy Star Rating

As mentioned, Energy Star-certified heaters are more efficient than non-certified models. So, if you’re looking for an energy-efficient tankless water heater, choose one with an Energy Star rating. That way, you can be sure that you’re getting a high-quality, energy-saving product.

Besides being more energy-efficient, Energy Star-certified heaters also have other benefits. For example, they often include features that make them more durable and easier to use. And because they’re more efficient, they generate less heat waste.

That said, here’s a cool video that may come in handy when choosing an Energy Star certified water heater:

Screenshot from a video discussing energy-efficient tankless water heaters
Courtesy of ESWaterHeaters

Look for a Heater With a Recirculation Pump

If you want your tankless water heater to be as efficient as possible, look for a model with a built-in recirculation pump. As the name suggests, the pump helps circulate hot water through your pipes, so it’s always available when needed. As a result, you won’t have to wait for the water to heat up every time you turn on the tap.

In addition, a recirculation pump can also help to reduce water waste. That’s because it circulates already-heated water, rather than you having to wait as the water that hasn’t been heated drains away.

Choose a Heater With a Self-Cleaning Function

A self-cleaning function is another feature that can help to improve the efficiency of your tankless water heater. The function helps to keep the heating elements clean, which in turn helps to improve the heater’s performance. As a result, you’ll use less energy and save money on your energy bills.

Besides, a self-cleaning function also helps extend your heater’s lifespan. That’s because it prevents the build-up of deposits, which can corrode the heating elements and other components.

Get a Heater With a Warranty

When you’re buying a tankless water heater, be sure to get one with a warranty. That way, you’ll have peace of mind knowing your investment is protected.

Most tankless water heaters come with a warranty of 5-10 years. But if you want an even more extended warranty, you can always shop around.

That said, if you need a reliable heater, try this FOGATTI Tankless Water Heater. It comes with a five-year warranty and free replacement if the unit doesn’t impress you within the first 30 days, so you can be sure your investment is protected.

The FOGATTI Tankless Water Heater installed against the front glass panel of a shower
Courtesy of

Final Thoughts

Tankless water heaters are more energy-efficient than traditional tank heaters. But to maximize your savings, choosing a model designed for energy efficiency is essential.

Here are the main things to look for:

  • A UEF of 0.95 or higher
  • An Energy Star rating
  • A recirculation pump
  • A self-cleaning function
  • A warranty of 5-10 years

By following these tips, you can be sure that you’re getting an energy-efficient tankless water heater that will save you money on your energy bills.


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