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How Many Watts Does a Hot Water Heater Use? Let’s Find Out Right Now!

Fact checked by Stephen Conklin

How Many Watts Does a Hot Water Heater Use

Are you having difficulty deciding which between gas and electric water heater to buy for your family? Choosing between these two household water heating systems is easy if you ask yourself “how many watts does a hot water heater use?”

Determining the wattage of a hot water heater lets you estimate how much money you will spend to enjoy hot showers. You can create a more appropriate budget for your family and relish the savings you get.

Table of Contents

Understanding Water Heaters

Water heaters are not different from your stove which consists of a heating element powered by a source. Most households have propane water heaters, gas-powered, natural gas, or other gaseous fuels to produce heat.

On the other hand, electric water heaters operate their heating elements by drawing electricity from an electrical outlet. Electricity passes through a coil, agitating the electrons within the heating element and increasing the temperature.

Regardless of the heat source, the water heaters we have today often come with a storage tank. Inside the tank are two heating elements with their respective controllers.

Gas or electricity heats the elements, slowly raising water temperature levels. The heated water then goes out through another port for us to use and enjoy.

Where Does Watts Come Into Play?


Some electrical terms are necessary to understand better how an electric water heater works, not only watts. Two of these are volts and amps. Let us use a water analogy to describe these two terms before we move to watts.

The water flows because of pressure – the greater the force, the faster the movement of water along the tube. We can liken this water pressure to an electrical system’s voltage. It pushes the electrons through the circuit until it reaches an electric appliance.

An ampere is analogous to the speed of water flow, which is often described as gallons per minute.

On the other hand, watts are the electrical energy that an appliance needs to operate. It is the product of current (amps) and voltage (volts).

That is why if your electrical system is not supplying enough current (amps) to the water heater, there is a chance that it may not work. Too much current can also damage your water heater.

How to Determine the Watts of a Water Heater


There are several ways you can determine how many watts a water heater uses.

  • On the water heater

The easiest way to know how many watts a hot water heater uses is by looking at the technical specifications label on the appliance. You should be able to see a sticker on the side of the tank near the power cable.

Companies purposefully placed this sticker on this section to make it easy for anyone to read critical information, including voltage, amps, watts, ohms, and other relevant electrical data.

If there is no sticker near the power cord, you can check the whole system for similar labels.

  • Search online

If you are like some people who prefer getting information from the internet, you can perform an online search. Some water heater manufacturers provide a search tool on their official websites to offer specific technical information about their products.

You can also try reviews, especially those that deal with a water heater’s technical specifications.

Forums and online communities are also worth checking. You can ask water heater owners about the wattage rating of your water heater.

  • Do simple math

Let us say the sticker on the water heater only shows the voltage and amperes and that you cannot find any other information from the internet. What will you do?

You should still be okay if you know your water heater’s current and voltage rating.

Remember what we said about power being the product of current and voltage? You can determine your water heater’s wattage by multiplying the volts by amperes.

Suppose you have a 240-volt, 20-amp water heater. In that case, your water heater uses 4,800 watts (240 volts x 20 amps). Pretty straightforward. Is it not?

How Much Power Does My Water Heater Use?

Determining the wattage rating of your water heater is the first step to learning how many watts it uses.

You must realize that your appliance’s wattage rating is a reflection of its power requirements over time. In our example above, the water heater uses 4,800 watts per hour. As such, determining how many watts your water heater utilizes depends on how many hours it operates in a day.

Let us say your family uses the water heater for four hours every day. Multiplying our 4,800-watt (4.8 kW) example by four will give us 19,200 watts (19.2 kW).

If you operate your water heater consistently for four hours every day, you consume about 576,000 (576 kW) every month or about 7,000 kW every year.

How Much Money Will I Need to Operate My Water Heater?

Knowing how much you will pay for using your water heater requires knowledge of your state’s current electricity rates. On average, US households pay 13.31 cents per kWh.

In our example, you will pay 63.89 cents per hour or $2.56 per day for using the 4,800-watt water heater for four hours. Computing further, you are looking at spending about $934.4 annually on water heating alone.

Of course, states have different electricity rates. If you live in Louisiana, you are in luck because the state has the lowest electricity rate in the country, at only 9.37 cents per kWh.

Families living in Connecticut pay as much as 21.62 cents per kWh. Using our example, they can spend as much as $4.15 per day or $1,515.13 annually.

Other states with a high cost of electricity include Hawaii (32.76 cents/kWh), Alaska (22.54 cents/kWh), Massachusetts (21.11 cents/kWh), California (19.90 cents/kWh), New Hampshire (19.63 cents/kWh), New York (19.3 cents/kWh), and Rhode Island (18.64 cents/kWh).

How About Gas-powered Water Heaters?

In general, gas water heaters are more economical to operate than electric models. The computation is almost similar to determining how many watts your electric water heater uses. It only differs in the unit of measure – ‘therm.’

A therm is equivalent to 100,000 BTUs. As such, if the water heater requires 100,000 BTUs to heat the water, you can say its power requirement is one (1) therm.

You can multiply the water heater’s thermal rating by the number of hours it operates in a day.

Let us say a gas-powered water heater uses 20,000 BTUs per hour or about 0.2 therms per hour. If you use the water heater for four hours, you will need 0.8 terms. The price of natural gas in the US is $0.93 per therm, on average. You will spend $0.74 per day or $271 annually.

What About On-Demand Electric Water Heaters?

While gas-powered tanked water heaters are more cost-effective than their electric counterparts, they are susceptible to heat loss. Heat can dissipate into the environment during storage and delivery to the different water fixtures.

If you want a more energy-efficient water heating system, you might want to consider an on-demand electric tankless water heater.


Determining how many watts does a hot water heater uses is as easy as 1-2-3.

  1. Look at the product’s label, search the internet, or perform a few calculations of your own.
  2. Determine how many hours your water heater will run every day.
  3. Multiply the wattage rating by the number of hours of operation.

Knowing the water heater’s energy consumption can help you decide whether to get an electric appliance or a gas-powered version.

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