New water heater requires electrical upgrade
Dear Angie: We just had a 3,800-watt, 40-gallon hot water heater installed. The installer told my husband that, at a minimum, we will need 20 amps. How can I tell how many amps I have?
Is it just a matter of changing that one breaker, or am I looking at a big electrical job? We’ve had no problem whatsoever with our electrical in the past. – Rochelle W., Fort Lauderdale, Fla.
Dear Rochelle: Based on the data you’ve provided, the installer of your water heater is correct. A 20-amp circuit would be the required size to operate the water heater.
This is determined by an Ohm’s law electrical formula: watts divided by voltage equals amps. I’ll even do the math for you. Divide 3,800 watts by 240 volts to determine that you’ll need 15.83 amps to operate your water heater. Circuits grow in size by five units of amperage, so you’ll need a 20-amp circuit to get the full benefit – and the expected amount of hot water – from your new heater.
Most likely, you already have a 20- or 30-amp circuit, both of which will do the job. The rated amperage should be clearly marked on your breaker handle.
You can safely downsize a breaker, say, from 30 to 20 amps. But if you upsize, for example, from 15 to 20 amps, you should be careful because the wire gauge may not be big enough to handle the additional load. If you find that you don’t have at least a 20-amp breaker, hire a properly licensed and trained professional to change it out.
As long as your electrical service has spaces for a new circuit, and your electrician is well qualified, it shouldn’t be a difficult or time-consuming job. Electrical projects can be dangerous, even deadly, for someone without training.
Angie Hicks is the founder of Angie’s List, a provider of reviews you can trust on contractors, doctors, dentists and other service professionals. More than 1 million consumers across the U.S. use Angie’s List to help make tough hiring decisions easier.