Electrical Load Calculator: How to Determine Your Home’s Load Factor

Load factor isn’t just electrician speak—it’s a term that can help you better understand your home’s energy use. Whether you’re trying to trim your electric bill or just curious about how your usage stacks up, calculating your load factor is a smart first step in improving the efficiency of your space. And good news: it’s easier than you think (no engineering degree or electrical license required). 

Average Electrical Load Per Square Foot

Electrical demand isn’t one-size-fits-all—different-sized spaces have different needs. Here’s how your home’s electrical load varies by square footage.

How to Calculate Load Factor

Believe it or not, your electric bill is a goldmine of information that can help you calculate your home’s electrical load with just a few key numbers. Don’t worry—no complex math or special tools required. Just grab your latest bill, a calculator, and get ready to crunch a few numbers.

Load factor = Total electricity (KWh) ÷ peak demand (KW) ÷ number of days in billing cycle ÷ 24 hours

Understanding Watts, Amps, and Volts 

Since home service panels are measured in amps ranging anywhere from 100 to 400, you’ll need to calculate the amperage of your service panel versus the total wattage of your electrical load. 

You’ll also need to factor in an additional safety margin of around 60% to 80%. In other words, you only want your electrical load to make up roughly 60% of your electrical system’s total capacity. Most experts advise that your safety margin should be no higher than 80%.

To perform your calculations, you need to understand the relationship between volts, amps, and watts. Here are the basic formulas:

• Watts = Volts x Amps 

• Amps = Watts / Volts

You can use these formulas to calculate the capacity of your home's overall electrical service. For example, let’s say you’re working with a 150-amp service panel. Since the main service voltage that enters a home is typically 240 volts, the calculation would be:

240 volts x 150 amps = 36,000 watts

80% of 36,000 watts = 28,800 watts

This means that a 150-amp electrical service should not be expected to accommodate an electrical load of more than 28,800 watts at once.

Who to Hire to Determine Load Factor

If you don’t have time to comb through your electrical bill or if you’d rather lean on the expertise of a professional, your local electrician can determine your home’s electrical load factor as well as provide tips for usage. They can also suggest upgrades that can help lighten the load (pun intended) and make your home more efficient when it counts the most.