What Size Generator Do You Need To Run A Water Heater?

Ossiana Tepfenhart
by Ossiana Tepfenhart

During Superstorm Sandy, most of my neighborhood was out of power. Having a warm shower felt like a distant memory, unless you had that one “bougie” neighbor with a generator. I was lucky enough to be friends with a millionaire’s daughter at the time. So, I got a shower. Part of getting that warm water involved knowing what size generator they needed to run a water heater.

Did you ever wonder how big of a generator is required for warm water? As it turns out, the answer to this isn’t exactly a “one size fits all” situation…

The generator size you need to run a water heater often depends on your house’s setup. Most homes will be able to successfully run an electric water heater and other parts of their home with a 5,000-watt generator. If you have a gas-powered water heater, then you only need 1,500 watts to run it successfully.

Getting warm water during an emergency is rarely ever the first thing we think about. However, it can make a world of difference when stuff hits the fan. Before you get a generator for your home, it’s a good idea to know what you should look for.

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What Size Generator Do I Need For A Water Heater?

How much power you need to keep a water heater going depends on a variety of factors, including how many appliances you want to power alongside it. However, the biggest factor that you have to worry about is the type of water heater you have. Here’s what you need to know:

  • A typical gas-powered generator only needs 1,500 watts to work. This means that getting your water heater powered could potentially be done by a fairly small portable generator if you have a gas heater. If you get a generator this low-powered, it’s worth noting that the water heater is the ONLY thing you will be able to power.
  • Electric water heaters will usually need a bare minimum of 4,500 watts to be properly powered. This also can help power certain appliances that require hot water, such as a washing machine.
  • If you have a smart water heater, you will usually still need 4,500 watts at a minimum. This is still an electric water heater. Just saying.

Generator Sizes For Water Heaters By Size

The general rules of thumb in the paragraph above are good to know, but it’s also important to remember that there are a bunch of different nuances that you should take into mind. While knowing what powers your water heater matters a bunch, it’s also important to keep in mind the size of your generator. We made a small table to help you figure things out.

Water Heater Size/Type of Water SupplyMinimum Wattage
Small Heater/Town Supply Water1,500 for gas/3,000 for electric
Small Heater/Water Pump3,000 for gas/4,500 for electric
Large Heater/Town Supply Water4,500 to 5,500 for all
Large Heater/Water Pump5,500 to 7,000 for all

Note: If you have a large water heater that’s electric and require a water pump to push water to your heater, you should err on the side of caution. Some models and water setups can require as much as 10,000 watts to power both, but this is fairly rare. Most homes can be powered by 7,500-watt generators (aside from the water heater) without too much issue. So, take that as you wish.

Can You Buy A Larger Generator Than What You Need To Power Your Water Heater?

Absolutely. The reason why you should know the minimum wattage for a water heater is to make sure that your generator will be able to power your heater at a bare minimum. As in, that’s the only thing it will be able to power. If you want to get a bigger generator, that’s not a problem. Just make sure that you use a surge protector if necessary, and avoid wasting energy on frivolous stuff.

An Important Note About Your Generator’s Usage During Your Power Outage

If you ever find yourself stuck on generator power, it’s important to remember that most large appliances will use between 3,500 to 4,500 watts. You can use a bunch of your favorite appliances, just not all at once. You will have to figure out which appliances you absolutely need, and what you can do without.

If you need to retain a lot of your home’s power during an emergency, you should consider talking to a generator specialist. They may be able to come up with a power solution that works well for you.

Can You Use A Portable Generator To Power Your Water Heater?

The biggest issue that you are going to have when selecting a generator is the number of watts that you can get out of it. One concern that many people have is whether or not they can power a water heater with a portable generator. The answer is usually no, simply because most portable generators don’t have 5,000 watts of power to them.

However, there are always exceptions to the rule.

It is possible to find portable generators that offer up as much power as a typical “permanent” generator. The highest-powered portable generators currently clock in at a whopping 17,500 watts. This means that it is very possible for you to power a water heater with a portable generator. You just have to make sure to buy the right one.

How Much Gas Do You Need To Use A Generator To Power A Water Heater?

I’ll be honest. Powering an electric water heater with a generator is impractical and should not be done unless you have no other choice. Generators can easily guzzle up to 25 gallons of gas per day (or more) for a 12,000-watt generator. Many families would be wise to take a break from powering their water heaters 24/7.

When buying a generator, it’s a good idea to ask how many gallons of gas it would need to be used continually in a day. Most generator sales companies will be able to give you a good estimate of the fuel you will need to have. If you are concerned about an upcoming storm that could knock out power, it may be a good idea to buy up some fuel ahead of time. You can never be too careful.

How Much Should You Expect To Pay For A Generator That Can Power A Water Heater?

It’s not going to be as cheap as those simple portable generators meant for power tool usage, that’s for sure. You should expect to spend at least $500 for a portable generator capable of pushing out 5,000 watts or more. The price can go as high as $2,000 or more if you need to have a heavy-duty generator that pushes out 10,000 watts or higher.

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Related Questions

Will a 20,000 watt generator power my whole house?

For the most part, a 20-Kilowatt generator will be able to power most of your appliances, a major central air unit, as well as most of your lights without issue. If you want to get a generator for your water heater too, then you may need to get a second unit.

How long can you safely run a generator?

You can run a generator for as little as a couple of hours to as much as a full 24 hours. It all depends on the make of the generator as well as the model that you have. It’s best to refer to your generator’s guide to figure out how long you can run a generator before it becomes a hazard.

Are whole house generators worth it?

Absolutely. Having a whole house generator can help you curb losses during a major weather event and can also help you keep your life together during disasters. Depending on the kind of damage that your area’s electric grid incurs, having a whole house generator can make or break your ability to keep your home intact. If you can afford one, get one.

Ossiana Tepfenhart
Ossiana Tepfenhart

Ossiana Tepfenhart is an expert writer, focusing on interior design and general home tips. Writing is her life, and it's what she does best. Her interests include art and real estate investments.

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