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How much electricity does a tankless water heater use?

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Did you know that a tankless water heater uses up a lot of electricity? Even tankless systems, which are more efficient than traditional tank boilers, use almost 17% of a home’s total electricity consumption, according to the US Department of Energy.

Tankless water heaters are some of the most energy-hungry home appliances, so it’s essential to know just how much power they use. It would help if you also considered whether a natural gas tankless water heater or propane tankless water heater would be more efficient for your needs.

A tankless water heater uses between 20 and 50 kWh per month, depending on the size of the unit and the amount of hot water used. 

How Many KWH Does A Tankless Water Heater Use Per Month?

Let’s start with some rough estimates. A family of four in a mid-size house requires an electric tankless water heater with a heating capacity of at least 18 kW.

Tankless water heaters remain inactive most of the time, only turning on when hot water is needed. They also rarely operate at full capacity, so while it may draw 18 kW for the first 30 seconds of usage, it will require less energy to run overall.

A family of four uses around 50 gallons of hot water each day. Traditional tank heaters may require many hours to meet this need, while tankless heaters are considerably more efficient. Consequently, this household will probably only need a single kilowatt-hour of power each day for their heater.

The heater, on average, runs at half capacity. If we assume that the average cost of electricity across the US is 15 cents per kWh, then:

  1. They can expect their electricity usage to be about 9 kWh daily, or $1.35.
  2. Every month, that’s 270 kWh or 40 dollars.
  3. Per year, that’s 3285 kWh or 493 dollars.

The standard cost of a water heater is around $510, which includes installation. However, when determining exactly how much energy your home consumes each year, you must keep in mind that it depends on how many hot water outlets are in your house and the ambient climate and your usage habits. Across states, the price of electricity does a tankless varies by several cents per kWh:

  1. If you live in an apartment or with only one other person, expect to use less power than the preceding number indicates.
  2. If you reside in a lower electricity cost state, you likely use much less energy than the prediction above.
  3. If you live in a cold-weather state with high power prices, expect to use more electricity than the estimate above.

Most electric heaters are efficient, meaning that almost all the energy goes towards actually heating water. Thus, calculations are more straightforward as you don’t need to account for wasted energy.

For the cost of $0.1319 per kWh for electricity, we can determine how much it costs to operate an electric tankless heater each month and each year:

Wattage Of Electric Tankless Heater

Cost Per Month (Rough Estimate)

Cost Per Year (Rough Estimate)

8 kW



9 kW



10 kW



11 kW



12 kW



13 kW



14 kW



15 kW



16 kW



17 kW



18 kW



19 kW



20 kW



21 kW



22 kW



23 kW



24 kW



25 kW



26 kW



27 kW



28 kW



29 kW



30 kW



The cost of running an electric tankless heater heavily depends on various factors. However, according to the Department of Energy, a tankless water heater uses less energy than a traditional water heater that operates on electricity.

Why Do Electric Tankless Heaters Need Such High KW?

At first, it may seem strange that supposedly efficient products come with high kW requirements. However, electric tankless heaters achieve their efficiency by using a lot of energy to heat water quickly.

To put it in perspective, a sizable electric tankless water heater uses up to 36kW when heating water. That’s a big difference compared to the average dishwasher, which only consumes around 1.8kW. Although tankless heaters need power for less time (usually under 10 seconds), most home hot water appliances, including old-style tank heaters, run for hours at a time. While a tank heater uses water all day long even when you’re not using hot water, tankless heaters quickly do their job and then go into resting mode. As a result, they save around 40% on energy costs in the long run.

How Do Electric Tankless Heaters Compare To Gas Tankless Heaters?

A tankless electric water heater often has high-efficiency ratings and la ong lifetime. They are also considered safer overall than gas heaters. Usually, these tankless electric models can produce about eight gallons of hot water per minute.

Gas heaters have a long lifespan if they’re well-maintained. However, you’ll need to schedule regular check-ups and cleanings by a professional technician. Over time, your gas heater may accumulate mineral deposits or require maintenance and flushing. Plus, safety inspections are always necessary due to natural gas being involved.

Gas and electric heaters use different amounts of electricity.


How Much Electricity Do Gas Tankless Heaters Use?

It’s important to note that modern gas-powered tankless water heaters are not powered by gas alone. Electric elements, such as the ignition system and controls, also exist in these devices. On the other hand, the amount of electricity consumed by these units is significantly lower than with fully electric versions.

So how much electricity does a tankless water heater use? For example, Rinnai gas tankless water heaters require two watts of standby power. However, before it throttles to 25 to 65 watts – depending on the water flow rate and temperature – using this gas tankless water heater for two hours will consume 50 to 130 watts (0.05to 0.13 kWh). Consequently, if you live in New York, where the average p/kWh price is approximately 19 cents, you’ll be paying around $29 monthly or $352 yearly.

Even though you’ll still be paying for your gas consumption, it will cost less than using an electric version. One reason tankless gas heaters are more expensive upfront is that they usually require professional installation because they need to be connected to a natural gas line.

These heaters also have a few disadvantages that must be considered before purchasing one. For example, these heaters are only effective at 180 degrees Fahrenheit or lower temperatures. Therefore, they cannot be used to achieve temperatures more significant than this, and they may not work correctly at higher temperatures. Furthermore, because they require ventilation to function safely and effectively, these heaters frequently need an extra installation that might be expensive.

How Much Money Can I Save By Using Gas Vs Electricity?

Electric tankless water heaters cost far less than gas tankless water heaters initially. When it comes to the initial expenditure of an electric tankless water heater, they cost far less than their gas counterparts. Electric whole-house tankless water heaters start at around $500 and can go up to $700, particularly for high-end systems with electronic ignition systems. That number does not include installation costs; see below.

Tankless water heaters that run on gas may be more efficient than those with tanks, but their efficiency only peaks at 80-85%. On the other hand, an electric tankless water heater is much more efficient, standing at 98+%. Even though natural gas is often cheaper per BTU of output power than electricity, this benefit is outweighed by the electric unit’s higher efficiency, longer service life, and more affordable installation. As a result, electric tankless water heaters cost less than most tankless gas models.

More importantly, gas prices are more volatile than electricity rates, and most economists agree that gas prices will rise significantly in the next few years. However, electricity rates in most areas should stay relatively stable or increase slower.

A gas and electric tankless water heater is similar in terms of operating costs, except that gas appliances usually require more regular maintenance. That last variable will be determined by the difference between natural gas or propane and electricity pricing in your region.

Gas costs are exorbitant in several parts of the world. Due to a lack of supply in the region, gas prices are incredibly high in many locations. In these areas, an electric unit can be considerably less expensive to operate. Remember that electric tankless water heaters are more energy efficient. Thus, much of the price difference between the fuels will be offset.

After running cost calculations, we found that:

  1. The most cost-effective alternative to oil is electric heat. Electric heaters are the most affordable electric heaters, costing $1.83 daily. The average daily cost of an electric heater is $2.32.
  2. Compared to other gas heaters, convection heaters are the cheapest to run daily, costing an average of $2.56.

Even though a reverse-cycle air conditioner has a higher initial investment (factoring in the appliance and installation), you could save money in the long run. Based on our research of 10 models, we found that the average running cost per day is $0.85, which would amount to $76.42 per winter.

How to Keep Your Bills to a Minimum

So you know how much electricity a tankless water heater uses. These water-saving tips will help you keep more money in your pocket by reducing water heating costs.

  1. Lower the thermostat

Most water heater thermostats come set to 140°F, but many households can do just fine at 120°F. So you probably won’t notice a serious temperature shift when you shower after adjusting. Just know that this slight decrease saves money, reduces scalding, and slows mineral buildup and corrosion in your pipes.

  1. Insulate tank

Insulating your storage tank (electric, natural gas, or oil) helps minimize heat loss and keeps the heater from turning on frequently. Make sure not to cover the heater’s thermostat, burner, or top and bottom according to the manufacturer’s recommendations. For assistance in insulating your hot water tank, contact your local plumber.

  1. Install heat traps

Heat traps prevent cold water from entering the tank and prevent heated water from leaking out of it. Built-in heat traps are standard in most modern water heater designs. Installing a heat trap is a viable alternative if your device is more than 10 years old (and in good working condition). For further information, contact your expert plumber.

  1. Use cold water

Many people don’t realize this, but using cold water for most of your electric load (including the rinse cycle) and for everyday hygiene tasks like brushing your teeth and washing your hands can help lower your utility bill. 

  1. Repair leaky faucets

A dripping faucet might not appear to be a big problem, but it can actually squander water and increase your utility bills quite profoundly. So be sure to fix any leaky faucets as soon as possible (that includes outdoor ones). Many people are unaware that 10% of residences have plumbing leaks that waste over 90 gallons daily!

  1. Drain the tank

It’s a good idea to empty your water heater every year. Draining the tank helps to free up sediment that can reduce heat transmission and, in the end, degrade the efficiency of the equipment. While this is a simple process, follow the manufacturer’s instructions carefully if you’re unsure. If you have any questions, contact a professional for assistance with water heater maintenance.

  1. Install a timer

A water heater tank that runs constantly is a waste of electricity. You can help conserve energy – and extend the life of your unit – by installing a timer to turn off your heater at night. For more information on water heaters, call your local plumber.

  1. Insulate pipes

Not only will insulating your tank help, but you should also consider adding insulation to the first 6 feet of the hot and cold water pipes connected to the unit. By doing so, you’ll be preventing fire hazards and helping conserve heat. As a result, your system won’t have to work as hard to reheat the liquid.

  1. Consider purchasing a new water heater

A water heater over 10 years old is an accident waiting to happen. They are inefficient and could cause severe damage if they leak or burst.

Summing Up

The gas vs electric debate is ultimately a case of personal preference. There isn’t a one-size-fits-all solution. Each homeowner has unique requirements. Therefore, they should make their own judgments. Many skilled experts believe that electric tankless water heaters are an excellent alternative. Our article gives you all information about how much electricity tankless water heaters use.

Water heaters with a water tank are excellent choices, particularly if your household’s hot water demands exceed the average. Unfortunately, their complex heat exchangers make it more challenging to repair and maintain in the field. 

However, they’re also an appealing option. Tankless water heaters are becoming increasingly popular for their longevity and excellent performance. Though the installation process can be costly, it is worth the investment to call a professional tankless water heater installation in Sacramento.

Read more on the topic:

  1. How Long Does a Tankless Water Heater Last?
  2. How Long Will It Take My Water Heater To Heat Up?
  3. What Causes Too Much Pressure in a Hot Water Heater?
  4. How Many Amps Does A Tankless Water Heater Use?
Mike Joshua

Mike Joshua, a 33-year-old plumber based in California. With a passion for solving complex problems and a commitment to his trade, Mike has dedicated the past 8 years of his life to honing his skills as a professional plumber. After completing technical college Mike quickly secured a job in a plumbing company and has been working steadily ever since. Mike's experience includes not only households but industrial gas and plumbing systems and installation, repair the equipment for different types of business He is known for his attention to detail, strong work ethic, and ability to complete projects on time and within budget. He is always striving to improve his skills and stay up-to-date with the latest industry developments and advancements. In conclusion, Mike enjoys outdoor activities such as hiking and camping. He also has a passion for DIY projects around the home and is always looking for new challenges to tackle.

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