A Step-by-Step Guide to Standby Generator Sizing


Home standby generators can be life-savers during prolonged power outages. When the power supplied by the municipal grid goes out, the standby generator kicks on automatically. If it’s properly sized, it will be able to keep everything from lights to refrigerators, air conditioners, and even complex, energy-hungry medical equipment running without interruption.

Choosing a properly sized generator is very important. A unit that’s too small won’t be able to keep up with the entire household’s electrical demands, while one that is too large will waste fuel. To make sure they get it right, homeowners should follow the step-by-step guide for standby generator sizing before moving on to investigate specific systems.

Step One: Decide What Appliances and Electronics Are Essential

The best place to start when sizing a standby generator system is by determining what appliances and electronics will need to be powered during an outage. Most families include lights, central air, refrigerators, freezers, pumps, and medical equipment on their must-have lists along with sufficient power to charge cell phones and laptops. Write a list of each item that will be tied to the standby generator to make the next step easier.

A few extras like televisions, microwaves, or crock pots won’t make much of a difference in terms of power draw and can dramatically improve residents’ quality of life during prolonged outages. Those who are willing to invest in a high-capacity generator also have the option of powering their entire homes. However, they’ll face higher initial investments than families that pick and choose what to power when the municipal grid goes down.

Step Two: Write Down Power Requirements

The next step is to revise the list created in step one to contain relevant power requirements. Check each appliance and electronic device and write down its power draw in watts. If the device only shows how much power it pulls in amps or volts, use an online calculator to convert the information into watts before writing it down.

For larger items that have electronic motors, multiply the power draw in watts by three. This will provide a margin to allow for the increased power draw that occurs when users start up the motors.

Add everything up to get an estimate of how much power the home will use during an outage in watts, then convert it to kilowatts by multiplying the total by 100. For those who aren’t mathematically inclined, there are also online calculators that allow users to fill in the relevant information and get instant power draw estimates.

Step Three: Contact a Supplier

Once homeowners know how much energy they’ll need to weather power outages in comfort and style, it’s time for them to reach out to suppliers. Keep in mind that electricians who specialize in backup generator installation have extensive knowledge in the field. Use the calculations above as a general guideline, but take the experts’ advice to heart.

The Bottom Line

Installing a properly sized standby generator is one of the smartest things homeowners can do to improve their properties. The generator will ensure that residents have access to all the power they need during even prolonged outages, will require only minimal maintenance, and may even raise the home’s property value. It will make an excellent investment.