How Many Amps Does A Water Heater Use? (Find Out Now!)

Upgraded Home Team
by Upgraded Home Team

People often tend to forget about things they grow used to in a home. A water heater is one of those appliances that are well hidden we tend to forget. The only time we know, it is there is when the hot water is not working.

When the electric bill comes in, we know the appliances are the most expensive on the bill. There may be one question that has you wondering about the most forgotten appliance. How many amps does the water heater use?

A standard electric water heater with a 4,500-watt heating element uses 18.8 amps. The average electric water heater runs at 240 volts and works with a 30-amp breaker. Gas electric heaters use 12 amps at 115 volts.

Electric Water Heater Amps

It is critical to know the amps so the home’s electrical system is not overloaded. Should this happen, it will continue to trip the breaker to keep the home safe. These are the factors that determine how many amps the water heater uses.

  • Heater Type
  • Fuel Type
  • Capacity
  • Energy Efficiency

It is critical to understand how many amps the water heater uses. There are different options on which water heater is the right amount of amps for the circuit breaker. Sifting through these four factors will help you understand the options to make an educated decision on the right one.

Tank Vs. Tankless Water Heater

Electric water heaters come in both tank and tankless varieties. A water heater with a tank constantly heats the water that it contains. However, tankless water heaters only heat water when you heat it for current use.

Traditional water heaters have tanks, and they are less energy efficient than tankless water heaters. You can lower your electric bill with a tankless electric water heater, even if it uses more amps than one with a tank.

40 Gallon Electric Water Heater

The most common sized tanks in a home are 40 gallons. If the tank needs to be replaced in an older home, the chances are good it will be the same size. If a professional is called out, most of the time, there is no charge to remove the old unit.

A 40-gallon electric water heater requires a 30 amp breaker. It will not use all 30 amps, but there needs to be enough juice for the unit to operate correctly. The most common amps for all appliances is a 30 amp, so no upgrades are required.

Tankless Water Heater Requirements

Tankless water heaters require 120 amps to operate. It is much higher than water heaters with tanks. Older homes only have from 100 to 200 amps and need an upgraded electrical system from a professional electrician.

One option they will look into is increasing the circuit breakers by adding a subpanel. This process will add to the amperage allowing you to use the tankless water heater safely.

Electric Vs. Gas

A water heater runs on electricity or natural gas to heat the water. The type of fuel needed to operate the water heater makes a difference in the amount of electricity used. We will look at both fuel types and their cost to work every month.

Electric Water Heaters

When purchasing an electric water heater, the cost is cheaper. However, the monthly bill to keep it running will cost more than natural gas. The average monthly bill for an electric water heater is about $42 per month.

When it comes to installing, it is cheaper than a gas unit. It is easier to install to the electrical system than to a gas line. Unless you are certified, it is best to let the professionals handle the installations when dealing with electricity or gas.

An electric water heater with a tank needs a dedicated 30 amp breaker with a 240 Volt circuit. No other appliances or electrical devices should be attached to this circuit. In some situations, there may be an electrical upgrade needed for installation.

A tankless water heater requires a 120 amp breaker. Older homes may need an upgrade, or they will trip the breaker or need to be reset. The technician should give an estimate to determine the cost.

Gas Water Heaters

The price of a gas unit costs 25 to 50 percent more than electric units. It is the monthly bill that will save you money in the overall payments. Natural gas costs about $30 a month to operate a gas water heater.

The cost of installation depends on these factors.

  • If the gas line is already there
  • If there is an upgrade required
  • The costs of labor per company called out

A gas water heater that has a tank needs 30 amps. Since this is the most common, most homes will not need an upgrade. Older homes have 100 to 200 amp service, so it will be sufficient to cover.

A tankless gas unit needs a 120 amp breaker. Older homes will need an upgrade to their electrical system to carry this unit.

Changing Fuel Types

The biggest reason people choose to go with natural gas water heaters is that natural gas is cheaper. Some want to convert from gas to electricity because they do not feel comfortable with gas lines. The good news is it is possible to convert from one to the other.

If you want to find out, the best way is to ask a professional and get an estimate. Most companies offer free consultations. Many will give you a good deal if they know you are serious about switching.

If you have electricity and want gas, contact the local gas provider to see if they service your area. If the company services the site, they may offer an estimate without coming out to the location.

These are the questions you should inquire about when contacting the local gas company.

  • Is the fuel type available in the location?
  • How much will it cost to install a gas line?
  • Are there any permits needed to put a gas line and water heater?
  • Is an upgrade necessary for the total amperage?
  • What will the monthly bill be on average for gas?

Getting the answers to these questions will give you the educated decision you need to make. It is expected to be expensive if you are starting from scratch, but factor in the savings.


After the proper amperage and circuits, the capacity is a significant factor. If the capacity cannot sustain the necessity, it does not matter if it is gas, electric, tank, or no tank. The size of the water heater has to be able to handle the household demands.

The capacity of the unit determines the amount of electricity used. For example, tanks come in 20 gallons to 80 gallons. The bigger the tank, the longer it will take to heat, and the more electricity it will burn.

The best way to factor how big of a tank is needed, start with a 40-gallon tank. A 40-gallon tank is sufficient for up to a three-person household. Then add ten gallons to each individual in the home.

Tankless Water Heater Capacity Calculations

Water heaters with the coils are calculated by the flow rate or gallons per minute. The more the flow rate, the higher the utility bill will be. Figuring out each appliance flow rate will have to be run simultaneously, then add them together.

An example would be running a laundry load, taking a shower, and having the dishwasher running. You will have to add the flow rates of them together. You can then figure it with each size of the tankless water heater systems to get an accurate estimate.

Figuring out the capacity will give you an idea of which one works in your favor.

Energy Efficiency Options Save Electricity

Studies and research prove that the water heaters count for 18 percent of the kilowatts used. It is essential to find the most energy-efficient unit to save money on the electric bill. Natural Gas is more efficient than electricity.

Upgraded Home Team
Upgraded Home Team

We are a team of passionate homeowners, home improvement pros, and DIY enthusiasts who enjoy sharing home improvement, housekeeping, decorating, and more with other homeowners! Whether you're looking for a step-by-step guide on fixing an appliance or the cost of installing a fence, we've here to help.

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