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Energy CostsIN CHARLOTTEMarch 10, 2022by AndrewWhat Size Whole Home Generator Do I Need?

You’ve thought about buying a whole home generator for the safety and wellbeing of your family. It seems like a big, complicated step. We’ll help with a major step – what size generator do I need? What will get the job done in an outage or an emergency?

If you’ve ever lost power after a storm or power outage, you know how frustrating it is. In addition to worrying about food spoiling in your refrigerator and freezer, your life comes to a standstill. A whole house backup gas generator can solve this problem by providing you with uninterrupted power in almost any situation.

How much power do you need from a whole home generator? We’re here to work with you and help you know what you need for your home, budget and safety.

What Do Watts Mean?

Let’s start by knowing what systems, electronics or devices you’d want or need to use in a power outage. First, just the question of want? Or need? is a key place to start. Is this going to be for nothing but vital uses, or a truly whole home system with everything in your house up and running?

Make a list with the essential items first. An example would be the refrigerator, a few lights, heating and air. The next part of the list can be the wants, or optional, or momentary devices you’d like to have. If you’re going as far as a whole house generator capable of powering everything in the whole house, that’s a huge difference to know.

Now, on the list, we’re putting down two numbers with each system or device. You need the starting watts and the running watts. This will be the amount of power needed to start each device and the amount needed as it continuously is on.

Examples and very general estimates include:

  • Refrigerator 1,200 watts/180 watts
  • TV 200/200
  • Dryer 6,750/5,400
  • Sump pump 2,150/1,050
  • Water heater 4,500/4,500
  • Central air conditioning 8.750/3,800

To determine what size generator you need to power your entire home, or the components and systems you need in an emergency, use these three steps:

  1. Make a list of every appliance, device or system you need.
  2. Add the starting watts and running watts of each thing on the list.
  3. Add both columns of total watts.

Think About Some Scenarios

  • The Basics

In this situation, the family is looking to have the fundamental, basic essentials be ok during a power outage. Here’s a list and the watts needed for this possibility.

2 lights  175 W

Water heater  4,000 W

Central air conditioner  4,500 W

Refrigerator  1,500 W

Phone and tablet charger  50 W

Total Power Level  10,225 Watts

  • Just About Everything

Here, the family wants all the devices and luxuries up and running the whole time during an outage or emergency. The whole home generator basically needs to be enough for powering the whole home.

15 light fixtures  1,225 W

Water heater  4,000 W

Central air conditioner  4,500 W

Refrigerator  1,500 W

Phone charger  50 W

2 laptop computers  150W

Microwave  1,000 W

Stove/range  3,000 W

Dishwasher  1,500 W

Washer and dryer  3,000 W

3 LCD TVs  450W

WiFi and cable modem  40 W

Garage door opener  2,300 W

Total Power Level  22,715 Watts

Watts to Kilowatts

Home generators are sold in measurements of kilowatts, so now we’ve got one more easy math problem to do to get the right generator size.

Watts to kilowatts is a 1,000 to 1 ratio. So for 22,715 watts, you’re looking at 22.715 kilowatts. For 10,225 watts, it’s 10.225 kilowatts.

The first family should look into a generator of 12 or more kilowatts. It’s safer to add, or error a little higher, with the kilowatt rating. The estimates on the list might be somewhat off or you could find out your “needs” are a little more in a given emergency. For the second family, they should look for a 25 kW generator.

And that’s it. Now you can be confident in knowing how to determine your  whole home generator electrical power needs as well as select the best sized generator for your home’s requirements.

What’s an Automatic Transfer Switch?

Now that you have that list of all the electronics in your home and their power level or watts requirements, you can do a little more math. Before going on though, you need to know and factor in a generator’s automatic transfer switch (ATS), if the unit you have or are considering has an ATS.

While some generators need to be manually turned on and activated in case of a blackout or outage, most whole home generators can act as automatic standby units. It will detect a power disturbance and automatically, about instantly, turn on and become the home’s power source. This is what the automatic transfer switch is for.

The ATS needs power itself to run. Generally, it’s about equal to the amps your main breaker panel uses. For example, if you have a 200-amp breaker panel, you need to make sure the generator’s ATS is also 200 amps.

Because amps are not the same as watts, you’ll need to do a little conversion: watts = amps × volts.

Once you’ve determined the wattage of your ATS, you need to add that number onto your list and do a little more easy addition to get your total needed watts load.

More Decisions about a Whole Home Generator

Although you’ve figured out how to know your property’s generator electrical power demands, that’s not all you have to take into consideration prior to buying and installing a new whole home generator.

Should it be a propane or a gas generator? How much is the generator’s expense increasing as the power level you need also goes up? After that there’s another big decision: which manufacturer do you select?

Our professionals will discuss your power needs with you and guide you in selecting the right product before moving forward with your generator installation. We will never pressure you to buy things you do not need, and we will always give you our honest opinion.


Your best bet? Hire an expert to do the job. South End Electric has the background and understanding to ensure a safe and smooth installation. We can provide everything you need when thinking about a whole home generator for your home and family. Our professionals provide whole-house generator sales and installation to meet your needs. See everything South End Electric can do for you. Call us direct at 704-368-4694.