How to Size a Hot Water Heater

When you need to get a new water heater, how will you know what size to get? There are big water heaters, there are small water heaters—get one too big and you waste money, get one too small and you won’t have warm and hot water when you want it.

For a tankless or traditional (tanked) water heater, one of the first things that you’ll need to determine how much demand will there be and the flow rate, which is the number of gallons per minute. How many different things might be pulling hot water at the same time? Whatever that answer is, you’ll want to have a big enough water heater to satisfy your family’s needs and requirements. Probably one of the things to keep in mind is if you’re in a shower and using another appliance, you don’t want to run out of hot water!

A fairly common flow rate for a shower is 2.5 gallons per minute. Water coming from a faucet to fill a clothes washer might be .75 gallons per minute. Water heaters are normally set at 120 degrees. You can figure that normal water coming through the faucet is about 50 degrees, so it will have to be raised 70 degrees.

A simpler way to determine how big a hot water for your family should be is consider how many people are in your family. It is common for a 50-60 gallon water storage tank to meet the needs of 2-3 people. An 80-gallon tank for 3-4 people, and a larger tank for four or more people.

For tankless systems, a collector of 1.5 gallons is often common, you might need a larger system in warmer climates. A tank larger tankless water heater may be too hot when not in use.

Another way to determine how big a hot water tank should be is to plan on 10 gallons of water per show. How many showers might be used in an hour? Do you use a dishwasher in the morning or evening when people shower? Add six gallon. Do you wash clothes too? Add seven gallons. This can give you a general idea of how big your water heater should be—without wasting money.

For your next water heater project in Maryland, be sure to call Real HVAC services!

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