Will a Generator Run a Hot Water Heater?

Water heaters are essential anytime and are one of the most critical appliances we need, even when there’s no main power.

Water heaters require a continuous output from a generator that meets a certain wattage threshold. That threshold will depend on the type of water heater, and specific generators will have an easy or more challenging time meeting that threshold.

In this article, we will dive into the hot water part of the water heater and answer some key topics like:

  • Will a generator run a water heater?
  • What size generator is best?
  • How do watts affect things?
  • What is a tankless water heater?
Water heater on a wall

Use a Generator to run a Hot Water Heater

Yes, a generator will run a hot water heater. The ability of a generator to run a hot water heater successfully will depend on the amount of continuous wattage it can output to your hot water heater.

The average water heater will require 4 kilowatts of continuous power from your generator to provide hot water on demand.

Not all generators can produce this output, as some types of smaller portable generators are only capable of outputting 2 kilowatts of power continuously.

Generator Hook-up Issues

Another obstacle to using a generator to power a hot water heater is the fact that most hot water heaters are permanent appliances and are usually connected to a home’s electric grid directly.

This fact means that even if your generator is powerful enough to power a hot water heater, you may have trouble hooking it up because of the specific voltage output needed by water heaters. This problem happens most with smaller portable generators specialized for home and appliance use. 

If you want to invest in a generator for home use, you should stay away from portable camping generators and focus on generators designed for home use.

Size Generator Needed for a Water Heater

Generators of any size can run a water heater, but you will need to make sure it can output enough watts to meet the continuous power demand and the start-up power demand of the water heater.

You will want to purchase a generator on the medium or bigger side to guarantee that your generator will have enough power output and the correct voltage for house appliances like a portable heater.

Plug Hot Water Heater Into a Generator

Yes, you can plug a hot water heater into a generator, but a generator will need to have the correct voltage output to accommodate it. Many hot water heaters will require a 220-volt source, which some generators aren’t designed for.

Most portable generators will not have the correct voltage for a water heater, while many residential generators will.

Watts It Takes To Run a Hot Water Heater

It takes 4000 or 4 kilowatts of power to run a water heater continuously. There is also a start-up power cost which will vary depending on the type of water heater.

How To Run a Hot Water Heater With a Generator?

To run a water heater with a generator, you will need to hook up both pieces of equipment. Here are the steps to do it:

  1. Create a power cable to connect the water heater to the generator. For this, you’ll need either a 10/2 AWG cable and a NEMA L14-30 plug or a 12/2 AWG cable and a NEMA L5-30 plug. The first option is used if you are connecting the water heater to a 240v generator outlet and the second one to a 120v outlet. 
  1. Once you connected the cable to the plug and your power cable is ready, you can connect the generator to the water heater. You’ll need to replace the existing connections in the water heater’s junction box with the wires of your own power cable. After that, you connect the power cable’s plug to the generator.

Always bear safety in mind when doing electrical work. Ensure the water heater’s power supply is off and all the tools and equipment are dry.

Furnace Home and water heating

Can a Generator Power a Tankless Water Heater?

Yes, it’s easier for a generator to power a tankless water heater than a tank water heater. Tankless water heaters only need to be powered when you need hot water, while tank water heaters need constant power to keep the water hot.

Can a Small Generator Power a Heater?

Typically small generators will not be able to power a heater. Most small generators are meant to be used as flexible, portable power centers for places where power is scarce, like camping and outdoor activities.
A water heater will need a generator designed for household use, has a large power output, and can transmit electricity at the correct voltage.

Does a Hot Water Heater Use a Lot of Electricity?

Compared to other appliances in the house, a water heater does use a lot of electricity. Water heaters with tanks will run three to five hours daily to keep the water hot. This statistic means tank water heaters will use around 12 to 20 kilowatts of electricity daily.
Tankless water heaters are more energy-efficient, using 24 to 34 percent less electricity than tank water heaters.

Geothermal heat pump water tank and pipes

Power of Generator Needed to Run a Water Heater

A water heater will use around 4000 watts to run a water heater. Some water heaters without tanks will use less energy, but they are more expensive models than their tank-using cousins.

7500-Watt Generator

Yes, not only will a 7500-watt generator run a water heater, but 7500 watts is enough power to power an entire house. With a generator of this size, you can run a refrigerator, water heater, oven, lights, freezer, and well pump.

As with any generator, you should not exceed the generator’s total capacity. You should become familiar with the wattage requirements of your appliances to ensure you aren’t using too many at once so that you don’t overload your generator.

An overworked and overheated generator can break down quicker and fry appliances if the voltage regulator fails.

6,500 Watt Generator

Yes, a 6,500-watt generator will run a water heater and most household appliances.

6500w Generator – appliances

Yes, a 6500-watt generator can power the most common appliances in an average-sized home. Some appliances have high power demands, so you will not be able to run every appliance simultaneously with a 6500 w generator.

5500 Watt Generator

Yes, a 5500-watt generator will be able to meet the demands of most household water heaters.

Some water heaters require more power output than 5500 watts, but this wattage should be enough for most commercial water heaters.

5000 Watt Generator

Yes, a 5000-watt generator can run most water heaters. A 5,000-watt generator will run a water heater. But your water heater shouldn’t hold over 40 gallons of water, or it will be hard for this type of generator to cope.

If you use a 5000-watt generator to run your water heater, be careful to unplug other appliances first, as you might accidentally overuse your generator.

4000 Watt Generator

A 4000-watt generator should be able to run a water heater in most cases, but you may encounter some issues since 4000 is the lowest recommended amount of power necessary.

Some water heaters will have a costly startup power demand, which a 4000-watt generator may not be able to output, and the continuous power demand.


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