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How to Size a Whole Home Generator

Choosing the right generator for your home is crucial for ensuring seamless electrical power supply during blackouts, storms, or other emergency situations. The process, however, can be more complex than simply picking the most powerful generator you can afford. In particular, special attention must be given to homes that rely on electric cooktops, water heaters, clothes dryers, and other high-power appliances. Below is a detailed guide on how to properly size a whole-home generator.

Use these steps as your guide:

Whole home generator Fry HVAC

Step 1: Calculate Your Home’s Peak Load

The first step in sizing your whole home generator is to determine your home’s peak electrical load, which is the highest amount of electricity you’ll need simultaneously. This will require a bit of math.

  1. List All Appliances and Electrical Devices: Create a list of all electrical appliances and devices in your home that you’d like to operate during a power outage. Don’t forget to include lighting, HVAC units, and power outlets.

  2. Find Power Ratings: Each device’s power usage is usually stated in watts (W) or kilowatts (kW). This information can be found on the appliance’s label, the owner’s manual, or through an online search.

  3. Calculate Total Load: Add up the wattage of all the devices you intend to run simultaneously. For instance, if you have an electric cooktop (5000W), an electric water heater (4500W), a clothes dryer (5000W), and other miscellaneous devices (2000W), your total peak load would be 16,500W or 16.5kW.

Step 2: Factor in Starting Watts

Many electrical devices require more power to start up than to run continuously. This is known as “starting wattage.” Appliances like air conditioners and some pumps may require up to 3 times their running wattage to start. So, ensure you account for this while calculating your home’s peak load.

Step 3: Choose the Right Generator Size

Generators are also rated based on their running and peak (or “surge”) wattage. Once you’ve calculated your home’s peak load, add a 20–25% buffer to account for future electrical needs or any miscalculations.

  • Example: If your peak load is 16.5kW, adding a 25% buffer would require a whole home generator with a minimum capability of about 20.6kW.

Step 4: Consider Fuel Type and Availability

Whole home generators come in various types based on fuel—natural gas, propane, or diesel. Each has its own pros and cons. Natural gas generators usually have a lower upfront cost but are less fuel-efficient. Diesel generators are more fuel-efficient but cost more upfront.  For most homeowners, a natural gas generator is the preferred choice due to convenience and cost. 

Step 5: Evaluate Special Circumstances

  1. Automatic Transfer Switches (ATS): These switches turn on the generator automatically when a power outage is detected and can help in managing the load efficiently.

  2. Inverter Generators: These are more energy-efficient and quieter but usually come with a lower power output.

Step 6: Seek Professional Help

While the steps outlined above will give you a good idea of the whole home generator size you need, consulting with professionals for an energy audit is highly recommended, especially for more complex electrical setups involving multiple high-power appliances.

Important Tips for Electric Appliances

  • Electric Cooktops: These can consume anywhere from 1000W for a small burner to 3000W for a large one. Induction cooktops can go up to 3600W.

  • Electric Water Heaters: The average electric water heater will need about 4500W. If you have a electric tankless version, this can skyrocket to 18,000W.

  • Clothes Dryers: These typically consume about 3000-5000W, depending on the model.

  • HVAC Systems: A residential HVAC system usually needs between 3000W and 5000W of power, but commercial setups can require much more.

  • Add 1000-2000W for each general-purpose circuit in your home. These are the circuits that power your lights and outlets.

By calculating your power needs accurately, considering starting wattage, and allowing for future electrical needs, you can pick the right whole home generator for your home. Always consult a professional for an accurate sizing and safe installation, and remember to adhere to all local electrical codes and guidelines.

That wraps up your comprehensive guide to sizing a whole home generator, especially tailored to homes that utilize electric cooktops, water heaters, clothes dryers, and other power-intensive appliances. Happy shopping!

Fry Heating & Cooling, a fully licensed and certified contractor in the Heating, Cooling, and Plumbing industry, ardently adheres to a Christ-centric organizational philosophy. Our faith-based foundation guides us in every aspect of our operations, driving us to serve our regional market with dedication, compassion, and integrity. We are steadfast in our commitment to providing Fast, Friendly, and Fair services to all our clients, ensuring prompt responsiveness, exceptional customer engagement, and equitable pricing. Our standards of professionalism and goodwill reflect our aspiration to honor our faith in our daily conduct, while exceeding the expectations of our customers.

At Fry Heating & Cooling, our team of certified technicians specializes in a comprehensive range of HVAC, plumbing, and commercial HVAC services, including installation, repair, and maintenance of air conditioning systems, furnaces, whole home generators, heat pumps, indoor air quality products, VRF Solutions, plumbing systems, and commercial chiller & rooftop units. With a legacy of excellence and a commitment to customer satisfaction, we are your one-stop solution for all your indoor comfort needs.

As an authorized dealer for top HVAC brands such as Trane, Carrier, Rheem, and York, we pride ourselves on providing our customers with the most reliable and energy-efficient equipment on the market. Our team stays current with the latest industry trends and technologies, ensuring we deliver cutting-edge solutions tailored to your specific requirements.

Fry Heating & Cooling is proud to service the top 10 residential HVAC OEMs delivering unparalleled customer satisfaction and industry-leading expertise. As a premier HVAC contractor, we specialize in servicing and installing top-rated brands such as Carrier, Trane, Lennox, Goodman, Rheem, York, Daikin, American Standard, Bryant, and Amana. 

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