Well, it depends. What kind of answer do you want?
If you only need a loose estimate (to get a sense of how much the unit will cost), use the general guidelines below:
Need a much more accurate answer? Just use our step-by-step instructions below.
Your peak hour demand is simply the amount of hot water you typically use in one busy hour.
The easiest way to determine your peak hour demand is to pick the hour you use the most hot water during the day. For example, most households’ peak hour demand is either 6am–7am or 7am–8am—when everyone is showering/preparing for the day.
Once you’ve determined which hour is your busiest (in terms of hot water usage), use the chart below to add up the maximum amount of gallons you’d use in that hour.
Once you’ve determined your peak hour demand, choose a water heater that has a matching or slightly higher first hour rating (you’ll probably see this listed as “FHR” on the tank).
What’s the FHR? It basically tells you how many gallons of hot water the tank can provide in one hour—starting with a full tank.
Every water heater has its FHR clearly labeled on the yellow Energy Guide sticker. But if you’re shopping online for a tank, you can find the FHR listed under the “features” or “specifications” section of the tank’s product page (seen below).
Image taken from an AO Smith tank water heater product page
For your convenience, you can request an appointment in one of two ways: