Sizing a Storage Tank Water Heater

Once you've decided on your fuel type, you need to figure out
what size water heater will give you enough of what you need.
If you're replacing your heater, give some thought as to
whether or not your previous model consistently provided
enough heat. If it didn't, then you're going to want to
upgrade to a larger size. Also give some consideration to
whether or not your family has any potential to grow over the
next decade. If you have plans to start a family or if your
mother-in-law is going to be moving in with you, you'll want
a larger heater as well. After you've taken all that into
consideration, you can appropriately size your new heater.

For storage tank heaters, there are two important factors in
sizing: the amount of water it holds and the recovery rate,
which is the amount of water it can heat in one hour. The
recovery rate is displayed as First Hour Rating (FHR) on the
Energy Guide sticker. Generally speaking, if you live in
a two-person household, you can get away with a 30 to 40
gallon heater. Three to four people require a 40 to 50 gallon
tank, and if you have five or more in your house, go with
a 50 to 80 gallon model. Gas heaters have a greater FHR than
electric units, so they have smaller tanks with the same EF
rating.

To get a more specific idea of your needs, estimate your peak
hour demand and find a heater that falls within a couple of
gallons of this number. Here are estimates for the number of
gallons used for each household task:

* Shower - 20
* Bath - 20
* Shaving - 2
* Shampoo - 4
* Hand and face wash - 4
* Dish wash by hand - 4
* Dishwasher - 14
* Food preparation - 5
* Washing machine - 32


Multiply these numbers by the amount of times they occur in
a peak hour to get your total gallons used. For instance, if
you have three people in your household that all take morning
showers, you'd multiply 20 gallons by three to get 60 total
gallons used. If you also run the dishwasher in that same
hour after your shower, add another 14 gallons to give you
a grand total of 34 gallons. This is your peak hour need and
what you should look for on the Energy Guide sticker. If you
have limited headroom where your heater should go, look for
"low-boy" models -- they're shorter and bigger around, but
have the same capacity as their taller cousins.