ScheduleorCall (720) 605‑7270

Return to all articles

What Size Generator Do I Need?

A generator is a nice, all-purpose solution if your house is the victim of frequent blackouts. When the lights go out, the generator kicks on and provides you with temporary electricity. But what size backup generator do you need?

This blog will explain how you can figure that out by delving into:

Do You Want to Speak to a Licensed Electrician to Determine Which Generator Is Right for You?

Contact Cooper Heating & Cooling for a free estimate and generator installation service with a 100% satisfaction guarantee and a 1‑year labor warranty. Our highly-trained technicians are happy to answer any questions you have.

How Generators Are Sized

Generator size is often measured by kW or kilowatt, a measurement for the amount of electricity generated. It’s important to note that larger generators need more fuel to produce uninterrupted power. If you get a generator that’s too big, you could be wasting fuel, while one that is too small might not power all of your critical appliances. It’s also important to consider safety. Larger generators tend to produce more exhaust, which can be a health and safety risk to your home. FEMA has excellent guidelines to guide you in safely using your backup power source.

Square Footage of Your Home

The square footage of your home can be an indicator when shopping for generators, but it’s important not to use the size of your house as your sole guide. Yes, a bigger house typically uses more electricity. Still, your appliances will have a much more significant impact on the total amount you need, especially if you aren’t using your central heat or air conditioning during a power outage.

The Amount of Electricity You Need

The amount of electricity you need is the best way to determine the generator size to buy. It can be challenging to get a solid estimate, but you can look at your daily electricity usage on your monthly bill to get a starting point. Remember, a generator is designed to offer emergency backup power, not to fully replace your local power grid. Try to keep your electric usage to a minimum until the grid is back up and running.

Your HVAC System (Fuel Type and Size)

One of the biggest draws on your electricity is air conditioning and heating. If you have an electric furnace or heat pump system, you rely almost entirely on electricity for heating and cooling. It may not matter much in mild weather if your HVAC unit isn’t operating, but reliable cooling and heating are necessary during extraordinarily high or very low temperatures. 

HVAC units can use anywhere from about 0.5 kW to more than 5.0 per hour of run time. That’s a lot of temporary power, which may mean you need a larger generator to handle the load. If heat is the primary concern, you may not need to worry if you have a gas-powered or oil-burning system that only uses electricity for the pilot light and thermostat.

Number of Electric Appliances You Have

How many appliances you have is a big part of determining generator size. Large appliances have a reasonably high electric load and may require a larger generator when running. Some examples of appliances you’ll want to supply backup power include:

  • Refrigerators
  • Freezers
  • Stoves
  • Water heaters
  • Washer and dryer
  • HVAC

In addition, you’ll want to consider entertainment devices such as televisions, computers, tablets, and phones. While these tend to use less power than major systems, the more people plugging in, the more power you need. If you have medical equipment that needs to run constantly, you should get a separate, small generator just for that reason. The United States Agency for International Development recommends using several small generators to get the best value when working with backup generators.

Starting Wattage Required

Every item you plug in or connect to your electric supply has a starting and running wattage. When calculating the load on your generator, it’s easy to use the running wattage, but that’s a big mistake. The running wattage is the power it takes to keep your appliances running once they’ve started up. The starting wattage refers to the surge when you first plug in an appliance. 

To get an idea of the generator size you need, you’ll want to use the starting wattage for all of your major appliances when running the numbers. After all, it doesn’t matter if your air conditioner can run on 0.5 kW if you need a surge of 3.0 kW to start; it keeps overloading the generator and shutting it down.

Importance of Finding a Trustworthy Electrician

To get the best generator for your home, you must work with an electrician you can trust. You want honest recommendations and a system that provides the level of power you need without adding on extras. Talk with electricians that may help you scale back your expectations and provide upfront pricing on your installation. Always look for an electrical company that is:

  • Licensed and insured
  • Well-regarded with a good online reputation
  • Willing to provide references 
  • Experienced

Have Questions About Backup Power and Installation?

Contact Cooper Heating & Cooling to talk about generator installation services today! We’ve been your go-to electrical services provider in Denver for more than 40 years. Join thousands of local homeowners in receiving our 5‑star service when you call for a free estimate!

Luke Cooper