Close this search box.

How to Pick The Right kW Size Generator For Your Home


When experiencing a bout of bad weather, most of us have the same thought: “I hope there isn’t a power outage.”

Not only are power outages inconvenient, but they can be expensive. According to the Galvin Electricity Initiative, blackouts cost approximately $150 billion a year due to spoiled food, damaged equipment and decreased productivity. That’s why more homeowners are turning to backup generators to protect themselves and their homes during storms and electrical incidents.

Investing in a backup portable generator can save homeowners thousands of dollars by keeping refrigerators and appliances running during power outages. Moreover, the right size generator can keep household members comfortable during extremely warm or cold months. 

When selecting a portable generator, it’s essential to choose one that’s the right size for your home. If it’s too large, you’ll waste fuel and money. But if it’s too small, you won’t be able to keep critical items working. So here’s a closer look at choosing the right portable generators for your home. 

How Generators Work

Before determining which portable generators are best for your residence, it’s essential to review how generators work. Most homes receive energy through transmission lines connected to power stations along the electric grid. These transmission lines may be damaged during extreme weather events, resulting in a power outage. Whole house generators don’t rely on external transmission lines, which allows them to supply power during poor weather.

Determining Standby Generator Power

Although all standby generators provide electricity during blackouts, they differ in size and capability. These machines are ranked by kilowatts (kWs), which measure how much power is consumed by an electrical appliance. One kW is equal to 1,000 watts — the higher the kW, the more essential appliances your generator can handle. To figure out how much power you need, you should evaluate how much energy your appliances and power-sensitive electronics require to be operational. Most appliances come with a compliance badge that shows the amount of power they use.

You mustn’t overload your home standby generator. If you connect more kWs than it can handle, it will trip the main circuit breaker and no longer provide power to your home or business. 

Standard Appliance Wattage

If you’re not sure how much power your appliances use, you can use the ranges below to calculate your wattage needs. Remember, you’ll need to consider all your appliances to know how much power your whole house generator will need to run.

Estimated running wattage ranges for various household appliances include:

  • Fridge or freezer: 600 to 800 watts
  • Electric Range: 2,500 watts per element
  • Microwave: 1,200 watts
  • Hot Plate: 1,250 watts
  • Coffee Machine: 400 to 800 watts
  • Toaster: 1,100 to 1,700 watts
  • Oven (Electric): 5,000 watts
  • Computer: 500 to 2,000 watts
  • TV: 100 to 350 watts
  • Hair Dryer: 1,200 to 1,500 watts
  • Vacuum: 700 to 1,400 watts
  • Lamp: 150 watts
  • Radiant Heater: 1,300 watts
  • Electric Furnace: 5,000 to 25,000 watts
  • Space Heater: 1,250 watts
  • Central Air Conditioning System: 2,000 to 4,000 watts
  • Window Air Conditioner: 600 to 1,500 watts
  • Water Heater: 2,000 to 4,500 watts
  • Water Pump: 1,000 to 2,000 watts
  • Sump Pump: 1,500 watts
  • Outdoor Lighting: 500 to 1,00 watts

Calculating Your Home’s Electrical Load

The electrical load of a home or business is measured in Kilowatts, which is the amperage used multiplied by the voltage. You don’t need to be an expert in electricity to determine your home’s electrical load. Anybody can calculate this number using the following formula:

  •  Calculate lighting and receptacle needs
  •  Add your required kitchen appliance circuits
  •  Add wattage amounts for any other appliances that use their own circuits (such as a furnace, water heater, air conditioner, sump pumps, well or septic pumps, and so on)

That number you came to will represent a kW rating that will supply your needs. If anything, most expert advice will tell you to choose a backup generator slightly above the number you came up with. By choosing the next size up, your backup generator will cover your whole house in an emergency without being too much. 

Example Calculations for Determining the Right Size Generator for Your Home

If you’re not mathematically inclined, figuring out the right size generator can still feel overwhelming. So, let’s look at two examples of homes and what the calculations for determining the size of their home standby generators might look like.

In example one, the person needing an accurately sized generator lives in a small one-bedroom home alone. The appliances and other electrical items they want to run include their fridge, freezer, coffee pot and an electric oven. They don’t live in an extremely hot or cold environment and don’t feel they’ll require an AC or heat source during a power outage.

This calculation looks like this:

Fridge + freezer + coffee pot + electrical oven = total wattage/1,000 = total kWs

When you input the maximum wattage for each item on your list, the equation becomes:

800 + 800 + 800 + 5,000 = 7,400/1,000 = 7.4 total kWs

In this first example, 7.4 kilowatts are the minimum requirements used to determine which size generator is correct. Portable generators are an excellent option since this is a relatively small number. While not as powerful as full home standby generators, portable generators should supply enough power for this person’s needs.

In example two, there’s a family of three with a young child. They have a three-bedroom home and want to be prepared with air conditioning in a power outage. Additionally, they’d like to have enough power to run their fridge, freezer, coffee pot, electric oven, one television, two lamps and two personal computers.

This calculation looks like this:

Air conditioning + fridge + freezer + coffee pot + electrical oven + TV + (lamp x 2) + (computer x 2) = total wattage/1,000 = total kWs

Before solving the complete equation, you’ll want to solve the items in parentheses: the two lamps and two computers. The lamps are 150 x 2, which equals 300. The computers are 2,000 x 2, which equals 4,000.

When you input the numbers for each item on the list, the equation becomes:

4,000 + 800 + 800 + 800 + 5,000 + 350 + 300 + 4,000 = 16,050/1,000 = 16.05 total kWs

In example two, the family needs at least 16.05 kilowatts. They’ll likely want a larger generator for power outages.

Do You Need a Large Standby Generator?

If you feel you don’t need many appliances during a power outage, you may want to choose a generator with a smaller kW rating. However, do not forget the unit will work in your absence, and if you’re not home to disable something like your air conditioning, and you haven’t sized the generator for that, it’ll trip the breaker. You will not have any power until you come home, remove the air conditioning from the load, and reset the breaker on the generator.

If you have a small home or experience infrequent power outages, you may be satisfied with a smaller generator. Conversely, if you have a large home or live in a storm-prone area, you might prefer a generator with more kWs. The stronger your generator is, the more comforts and luxuries you can enjoy.

If You’re Still Not Sure…

If you’re still unsure what your power needs are for a generator for your entire home or one with enough energy to run a few significant appliances, reach out to an expert. They can also help determine whether you have more power requirements than you initially thought or if you’re right on track. 

Contact an Expert Today

If you’re considering purchasing a generator but unsure what size you need, consider contacting an expert for guidance. At Platinum Electrical Contractors, we offer a team of experts available 24/7 to help customers find the best-sized generator for their homes. We offer free, no-obligation consultations that can take place either in your home or virtually. Contact Platinum Electrical Contractors to get a free size assessment and installation quote today.

Share this post:

Comments on this post are not allowed.

The #1 Authorized Generac Home Standby Generator Dealer in Ontario

Generator Sales
Generator Service
Useful Resources

Call Sales

Call Service

Thank You For Requesting a Quote!

A member of our team will be in touch shortly to discuss how we can help to meet your needs.