What Size Generator Do I Need? Calculator and Tips

In this article, you’ll learn what size backup or emergency generator you need for your home.

After experiencing an EF4 tornado, I learned what it’s like to live without electricity for over a week. It’s easy to forget about all the things we use electricity for until you don’t have it anymore! Backup and Emergency generators are extremely important for these extended emergency situations (or even just keeping your lights on during a thunderstorm).

Our team includes two engineers with over 60 years of combined experience with electrical systems. One has designed and wired multiple homes, and has installed multiple backup generator systems over the years.

Below, you’ll find tons of information on choosing the right-sized generator for your needs. I built a backup generator calculator below, as well, which will provide you with an accurate generator size suggestion based on the appliances you need to run.

Common Types of Generators

There are several types of generators that can be useful in an emergency situation. Which one you should choose depends a lot on your situation. I, personally, have a portable generator, but you may want a different type.

• Portable generator: Portable generators are versatile and cost-effective. They’re best for powering only essential appliances during short-term outages, but I wouldn’t recommend them for a more long-term emergency. Typically, they only produce 2,000-5,000 Watts.
• Standby generator: These generators are permanently installed and connected to your home’s electrical system. They have a much larger watt output, usually ranging from 7,000 to 20,000 Watts, which is enough for an entire home. They are more expensive, though I’ve also found them more reliable.
• Inverter generator: Inverter generators produce a steady flow or power, making them a better option for sensitive electronics like laptops and medical devices. Usually, they only produce a small amount of power, around 1,000 to 4,000 Watts.

How Much Power Do You Need?

Before you buy a generator, it’s important to figure out how much power you’ll need during an outage.

Typically, you won’t need to run your whole home during an outage. Instead, you’ll want to focus on critical devices like medical equipment, refrigerators, and heat systems. Don’t forget the small things, too, like phone chargers.

Each appliance has two wattage ratings: starting watts (to power it on) and running watts (to keep it on).

Some devices that have motors, like refrigerators and air conditioners, require extra power to start. In these cases, you’ll need to buy a backup generator to handle these surge watts without overloading.

Calculating Wattage Requirements

So, how many watts do you need? The most accurate way to calculate is to figure out exactly how many watts each appliance you want to run requires. Then, add all the appliances together to determine the amount of energy your backup generator will need to produce.

All of this can get very complicated, though, and take a lot of time. Plus, I had a hard time determining the wattage requirement for some of my appliances. While I found some of my appliances had labels with this information, some did not or was hard to find.

So, I developed this backup generator size calculator to help you quickly get an estimate for your backup generator needs.

What Size Generator Do I Need? – Generator Size Calculator

Using this generator size calculator is easy. Just select the devices you want your generator to run, press the calculate button, and it will suggest a generator size.

My Emergency Generator Recommendations

Based on your specific generator size recommendation from the calculator above, here are some specific models that I recommend:

• Below 2,700 W: Eco Flow Delta 2 (Also Here on Amazon)
• Below 5,000 W: Eco Flow Delta Max 2000 (Also Here on Amazon)
• Below 7,200 W: Eco Flow Delta Pro (Also Here on Amazon)
• Below 13,000 W: DuroMax Dual Fuel Generator
• Below 14,500 W: Westinghouse Tri-Fuel Backup Generator
• Below 18,000 W: Westinghouse 18,000 Home Generator
• Below 22,000 W: Generac 7043 22kW Standby Generator
• Below 28,000 W: Westinghouse 28,000 Home Generator

Generators tend to get more expensive as the wattage increases. Other factors, like the type of fuel used, also influence price. If you’re on a budget, I recommend buying a generator to power just the essentials.

What About Solar Generators?

Solar generators have come a long way in the last few years. For instance, Jackery and EcoFlow have some very high-quality solar generators that I would absolutely recommend if you want to go the solar route.

Solar generators have some very big advantages. They’re silent, which is extremely helpful if you live somewhere with noise restrictions. They also have a low operating cost, and you won’t have to store fuel. They use the sun, after all!

However, there are also some very big downsides to keep in mind. Power generation will be limited on cloudy days and at night. You’ll need to invest in some batteries if you want to keep your heater on all night, for instance. Solar generators also typically have a lower output, in my experience.

Jackery’s current highest-producing solar generator is the Solar Generator 5000 Plus, which produces around 7,000 to 14,500 watts per hour (in perfect conditions). If you have a generally lower wattage need, like around 10,000 watts, a solar generator could be a great choice. Based on my research, there aren’t currently any solar generators that produce much more than this, though, so they still aren’t going to run your whole home!

If you have a low wattage need, according to the calculator above, Jackery has tons of other options, too. For instance, the Jackery Solar Generator 2000 Plus Kit has a max output of 3,000 watts.

I also have some experience with EcoFlow generators, which I would also recommend. Currently, the EcoFlow Delta Pro Ultra has the highest output at 7,200 watts. I also really like the EcoFlow Delta Pro 3, which is more portable and produces 4,000 watts.

We also have a full review of the Oupes Exodus 1500 Portable Power Station and the Bluetti Elite 100 V2 Power Station .

Accessories You Will Need

When I set up my backup generator, there were several accessories I ended up needing:

• Extension cords: I’d recommend a heavy-duty, outdoor-rated cord with a pretty high gauge. This isn’t an area you want to skimp on, especially since these cords aren’t terribly expensive, anyway.
• Fuel stabilizer: When storing fuel, you’ll need to add a stabilizer to prevent degradation. See out top picks in our Best Fuel Stabilizer guide
• Gas Cans: Find our Favorite Gas Cans for Long Term Fuel Storage here.
• Generator cover: If you’re going to put your generator outside, it’s important to have a cover.
• Transfer switch: For a home backup generator, it is much easier to have a transfer switch that uses your homes wiring instead of running extension cords everywhere. Basically, this device transfers some devices from in your homes electrical system from the power grid to the generator. It prevents you from feeding power back into the grid beyond your house. You can DIY yourself a solution to installing this, or you can have an electrician do it.

Here is a good video explaining what a transfer switch is and how to install one. Skip to 1:30 for a nice diagram and explanation.

Resilient Power Usage Tips

In my experience, how you use your backup generator is just as important as which one you buy. Here are some tips I’ve learned from experience to make the most of your generator, especially during an extended emergency:

• Alternate running high-power appliances like your refrigerator and heat system. For instance, if it is cold, foods that need to stay cold can be put in a protected outdoor area, like a garage. Then, you can focus your wattage on running your heat.
• Consider only running your generator for a few hours at a time. This will allow your refrigerator/freezer to cool down and your gas heat system to warm up your home. Then, turn it off for a few hours.
• If you have multiple devices that have high starting watts, don’t start them all at once. Turn them on one at a time instead.
• Devices that have electric heaters like electric stoves and forced air heaters consume a large amount of power. Consider alternatives to these like propane or natural gas.
• Try to stick to the essentials as much as possible. Yes, having a TV or computer is nice, but having a working generator is even nicer.
• Store extra fuel well. I wouldn’t recommend storing fuel in the same place you store your emergency food, for instance, and it shouldn’t be kept in the garage, either. Somewhere climate-controlled and ventilated is preferable.
• Don’t forget about maintenance. Most backup generators require oil changes and filter checks.
• Make a checklist before a power outage of the devices and circuits that are essential.

Wrapping Up

A backup generator is one of the easiest ways to keep things somewhat normal during a power outage (and it can be downright lifesaving in an emergency).

How do you know which one to get?

Use our calculator above. Then, look at our suggested generator list for a solid option.

For those living in apartments, take a look at our best generators for apartments review. This review was done by Jason, who has an engineering degree and extensive experience with generators.

I’d also recommend looking at my Power Outage Preparedness Guide. After all, preparing for a disaster is more than just getting a backup generator, and this checklist helps ensure you aren’t missing anything!