How Big of a Generator do I Need to Power my House During a Power Outage?

Most American homes lose power for a few hours every year. Sometimes it’s just an inconvenience. Other times homeowners can experience loss of food, frozen pipes, or even a loss of pay if you work from home. Even worse, it can put your family in danger due to the cold or medical needs. A generator can help keep your power going so you don’t face these losses.

There are lots of generators to choose from and prices range from hundreds to thousands of dollars. Small generators might not power enough for your needs, but a larger generator might require more fuel than you can keep on hand. It’s best to get something based on your specific needs.

So, how big of a generator do I need to power my house during a power outage? In this article, we’ll look at the different generator sizes to help you decide the best generator for your needs.

Generator Sizes

Generators are sized in wattage. The amount of wattage, or the size generator, you need will depend on what you want to run during the outage. This will be largely determined by the types of outages you want to be prepared for.

Determining Your Wattage

Step 1 – list all of the devices you want to power during an outage.

Step 2 – list their wattages. You’ll find the wattage on their labels. Look for the consumption wattage- not the output wattage. For example, an 800w microwave oven can require 1300w to run. Add a little more wattage than you need for those momentary power spikes as large appliances, such as refrigerators and air conditioners, are cycling on.

Note – if you can’t find the wattage, you can calculate it: wattage = voltage x amperage.

Step 3 – add up the wattage of all the devices.

This chart shows the typical wattages for the most common appliances (the actual wattage may vary):

Appliance Wattage
Smartphone charger 20W
Home security system 100W
Laptop 250W
46” TV 380W
Refrigerator 700W (2900 starting)
Garage door opener 720W (1420 starting)
Gas or propane furnace 800W
Sump pump 900W
10 lights 1000W
10K BTU air conditioner 1000W
Coffee maker 1000W
Toaster oven 1200W
Hair dryer 1200W
Washing machine 1200W
Well pump 1250W
800W Microwave 1300W
Space heater 1500W
Dishwasher 1500W
Electric range 2100W
2-ton central heat and air 3,800W (8750 starting)
Water heater 4500
Dryer 5400W (6750 starting)
Electric furnace 15,000W

This chart can help you determine how many watts to power a house with a generator based on the most common household needs.

The Types of Generators and Their Wattages

Here’s a look at the different types of generators and their wattages, along with what they’re best suited for.

Don’t rely completely on maximum power. A generator is only meant to run at maximum for a short period of time (around 30 minutes). Instead, look at rated power. This is the wattage the generator will produce most of the time.

Recreational – up to 2,000 watts

At around 60 pounds, this is the lightest generator. They’re the least expensive. They’re quiet and are easy to store and handle. You can use multiple generators to increase the output. They can power most devices that use a standard plug.

They’re too small to power large appliances. They can’t be connected to a circuit breaker. The more expensive units cost the same as a mid-size portable generator and don’t do as much.

These are ideal if you rarely have power outages and you just want to run a few small things such as a cooker, TV, or coffee pot.

Mid-size portable – up to 3,500 watts

At 150 pounds, these are still lightweight and they’re not very large, making them easy to handle and store. They’re quiet and can run smaller appliances.

They only power 110-volt outlets with two or three prongs, so they can’t run water pumps of large heaters and ac units.

These are great if you rarely have power outages and you want to run small appliances, a refrigerator, a small air conditioner, or a space heater.

Large portable – up to 7,500 watts

At around 300 pounds, these generators provide a good capacity for their cost. They can be connected to your breaker panel to power water pumps and other equipment.

Connecting them to your home to your breaker panel requires extra hardware, which can be expensive. They’re louder than inverters and other home generators and require more fuel. It needs to be protected from the rain and snow.

They’re ideal for occasional power outages and when you want to run larger appliances, dryers, water pump, ac units, heaters, etc.

Large invertor – up to 7,500 watts

These provide steady power which is great for electronics and can run refrigerators, central heat and air units, and they can be connected to your breaker panel to power well pumps, and more. They’re quiet and fuel-efficient.

Large invertors are expensive, costing as much as $4000 for a good unit, and they still require gasoline.

They’re ideal if you have occasional or frequent power outages and want to run larger appliances, ac units, heaters, dryers, etc.

Home standby – up to 20,000 watts

These can be permanently installed and they automatically come on when there’s an outage to provide uninterrupted power. They can power the entire house (according to their wattage rating). They can run on natural gas or propane.

This is typically the most expensive type of generator for home use. They can cost many thousands of dollars and can’t be used in areas prone to flooding.

They’re ideal for prolonged outages and areas with severe weather such as hurricanes, blizzards, etc., when you need to run appliances that are hardwired, such as central heat and air conditioning, water heaters, well pumps, etc.

Ending Thoughts

No matter what your needs are during a power outage there’s a generator that will work for you. I recommend getting the smallest generator that fits your needs. If it’s too small then you’ll overload the generator. If it’s too large then you’ll pay more than you need to in order to own, operate, store, and maintain it.

Remember, safety first – Never run the generator in the house. Generators produce carbon monoxide (CO) – a poisonous, odorless, and colorless gas that kills many people per year. Keep generators 20 feet away from your home.

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