Will A 5000 Watt Generator Run A Hot Water Heater

  • By: Umer.A
  • Date: October 10, 2021
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To run a hot water heater, a 5000-watt generator is a good choice. With snowstorms, there’s always an uncertainty of electricity outage. So, you should be prepared for these unannounced power outages, especially if you live in remote areas. Because once there’s an outage, your heating devices will lose power.

How big of a generator do I need to run a water heater?

Water heaters have a higher consumption because they generate heat from electricity. To heat water reservoirs, they require high wattage. If a water heater requires a lower current, it won’t heat properly.

Water heaters usually require around 4000 watts to heat water. And for this, a generator of 5000 watts would be perfect. This will make sure you’re following all the rules and regulations provided by generator manufacturers. That is to leave a 20% gap in the generator’s ratings and the total load.

But keep in mind, while you’re using the generator, you can’t use anything else, only a few LED bulbs. If you put on any other load, you’ll end up damaging the generator.

Can you hook up a hot water heater to a generator?

Whether a generator can be hooked with a hot water heater or not, you’ll have to check their compatibility. Here’s how you can check it.

The first step would be to find out the voltage required by the heater. They usually have 230 volts. But it’s better to check it before installing. Then you’ll have to check whether your generator can provide the required volts, in this case, 230 volts. It’ll be mentioned on the generator’s side panel or its owner’s manual.

If both voltages are the same, you’re good to go.

If your generator is limited to 120 volts, a 240-volt heater won’t heat properly. And if the generator can supply 240 volts, but the heater only supports 120 volts, the high voltage will damage the water heater.

How to connect a hot water tank to a generator?

Once you’ve found out if your generator and heater are compatible, you’re ready to connect them. A water heater can be connected through these two methods.

Connecting through Transfer Switch

Install a transfer switch near the water heater. In this transfer switch, connect both the house wirings and the generator’s connection.

The transfer switch will cut off the power completely from the generator or utility line. It’ll make sure your generator is not backfeeding into the system.

Connecting through an extension cable

Another method to connect the generator with the water heater is through extension cables. This is a cheaper method if money is tight. Make sure to get a better gauge cable as the heaters use a high current. Plug in the extension cable into either the 120v or 240v outlet of the generator. And then run the wires to the water heater. Plug in the water heater’s switch, and you’re good to go.

One thing to keep in mind is to turn off the circuit breaker of the generator when starting. So, when the generator gets a stable rhythm, you can turn it on.

How many watts does a water heater need?

Water heaters come in all sizes. The size of these heaters depends on the number of residents at your house. They can be anywhere from 20 gallons to 50 gallons. Depending on this size, the consumption of your water heater varies.

A typical water heater uses 240v current and around 16 amps. It requires 4000 watts to heat the water in its reservoir properly,

Whereas a 120v heater consumes less than half the wattage of a 240v heater. But it won’t be as efficient.

Can I run a pump with the water heater on a 5000-watt generator?

Using a water heater alone won’t do the job. It needs to be filled to work properly. Or else, it’ll be heating the air inside the reservoir. That’s why you should prepare yourself for the worst in an outage.

A water pump would be perfect for the job. It’s powerful enough to fill the reservoir quickly. For example, a 1HP well pump has 2000 running watts. But, it has high starting watts. That’s because it uses an electric motor, and electric motors have high starting watts. So, 1 HP well pumps have up to 4000 starting watts. Meanwhile, a water heater has 4000 watts. If you combine all these watts, you get 6000 running watts and 4000 starting watts.

So, you’ll need a generator that can power the pump and the water heater simultaneously. A 10,000-watt generator would do the job.

Once the water pump is up and running, the generator will have extra running watts for use. You can then switch on the lights in your house, and use the entertainment appliances too.

Can a 240V water heater run on 120V?

Yes, a 240V water heater can run on 120V, but there’s a catch. The 120V current is not high enough to fully heat the element inside the heater. As a result, it’ll take much longer to heat the water reservoir in the heater.

How many watts does a water heater need?

The water reservoirs in the water heater can be as big as 50 gallons. That’s why they require high wattage to heat up properly. A 240v water heater will consume around 4000 watts. At the same time, a 120v water heater can consume as high as 2200 watts.

What size generator to get if I want to use a water heater with other appliances?

To determine the size of the generator, you’ll have to calculate the watts of these appliances. And then, add them up for a total. This total will then be added to the water heater’s consumption watts. That is typically around 4000 watts.

How many watts does a 10-gallon water heater use?

A 10-gallon water heater is used in kitchens as it’s big enough for cooking only. These water heaters are of smaller size, that’s why they don’t require that much current. They require around 1900 watts at 120v.

Are tankless water heaters better?

If you live in a developed area, with a continuous supply of electricity and gas. Then getting a tankless water heater would be a better choice, as they only heat water when used. But if you live in a remote area, with outages, a water heater with a reservoir is the only option.


If you want to use a water heater, a 5000-watt generator is an excellent choice. It is powerful enough to power both 120v and 240v water heaters. With a 120v heater, you get enough watts to power a few electric appliances at home.

But, before connecting these, keep an eye on the compatibility in their voltages. They should have matching voltages of either 120v or 240v for best efficiency. Once everything is set, start the generator and enjoy the warm showers in cold winters.