Replacing a water heater is not on the typical homeowner’s list of most fun things to do. But when the water heater wets the bed, one has little choice but to replace it. The decision to replace it is immediately followed by a question: what size tank should I get?
This assumes that a homeowner decides against a tankless model. Tankless water heaters do have their advantages, but they also have disadvantages. Most homeowners will choose a traditional tank model when it comes time to replace.
Water Heater Tank Sizes
A standard tank water heater is essentially a large reservoir with a built-in heating element. It keeps water hot so that it’s ready for use on-demand. The types of water tanks installed in residential homes can range from 20-80 gallons of capacity. I have seen water heaters as small as 6 gallons and supersized heaters with capacities of 100 gallons.
The typical residential water heater has a 20–55-gallon tank. That’s the starting point if you’re trying to figure out what size tank you need for your family. But note that family size isn’t the only factor. You also need to consider whether the tank will be powered by gas or electricity.
How to Choose the Right Size
While there is no single formula for determining the right water tank size, Salt Lake City’s SameDay says that heating and plumbing contractors tend to follow some standard practices. Based on family size, heating source, and what would be considered normal usage, here are the general recommendations:
- Family of 5+: 80 gallons (electric) or 50 gallons (gas)
- Family of 3-4: 50 gallons (electric) or 40 gallons (gas)
- Family of 2-3: 40 gallons (both electric and gas)
- Family of 1-2: 30 gallons (both electric and gas)
Perhaps you noticed that there are no differences in capacity for the two smallest family units. But when you get into larger families, a higher capacity tank is recommended when you are heating with electricity as opposed to gas. There is a reason for this.
Consumption and Heating Speed
The differences are based on water consumption and the speed at which a water heater heats water. A gas water heater works faster than an electric model. So right off the bat, you’re going to have more hot water available more quickly.
Now consider larger families. Peak time in most households is first thing in the morning when family members are showering and getting ready for work in school. A larger family needs enough hot water to satisfy everyone. So if a water heater is powered by electricity, a family needs more in the tank to keep up with demand.
Consider First-Hour Rating
Something else homeowners should consider is first-hour rating (FHR). FHR is a measurement of the amount of hot water a unit can deliver in one hour of peak demand. Let’s say peak hot water time at your house is first thing in the morning. How much hot water can your tank deliver while everyone is getting ready for the day?
Experts recommend choosing a water heater with an FHR high enough to slightly exceed your calculated peak consumption. Given that a typical shower can use about 20 gallons, a family of four would need a tank capable of producing 80 gallons in an hour.
The tips offered in this post are ultimately just a guideline. The best way to figure out what size tank you need is to consult with an experienced plumber. Better yet, bring in two or three plumbers to get as many opinions as you can.