Many houses come with water heaters already installed in them, but many people find that these water heaters are too energy inefficient or too small for their family. Many home builders simply install the cheapest hot water heater they can find and give very little thought as to whether or not it is the right size for the house they have built, much less the right size for the family that lives there.
When it’s time to replace your water heater, use this guide to determine which size water heater is right for your home and your family.
To start, it is important to realize that it is not always the best idea to simply install the largest water heater you can fit in your water heater closet. A larger tank means that the heater will heat and hold the temperature of a lot more water. This can increase your electricity or gas bill, and waste resources you don’t have. A tank that is too small, however, means that your family will constantly have to argue over who used up all the hot water before every bath and shower. It may also mean that you have to schedule the use of showers, clothes washing, and dish washing.
The solution is to figure out the exact right size water heater for your family. Start by figuring out how many people in the household need hot water. Obviously, this means any permanent residents, but also figure in the proportional use of guests and temporary residents. For example, a college student who is only home four months a year would count as 4/12 or 1/3 of a water consumer. Make the best guess you can for irregular guests. Multiply the number of water consumers by twelve.
Next, compute your home’s maximum water occupancy. This is the number of bathrooms in the house plus 1. This number represents everyone using a shower while also running a dishwasher or a load of laundry. Multiply this number by the number you calculated in the previous step. For example, a home with three bathrooms would have an occupancy number of 4. A house with four full time residents would have a consummation rate of 48. Multiplying these numbers together gives you 192. This result is called the FHR.
An FHR or first hour rating is a measure of exactly how much hot water the water heater can deliver. Every hot water heater is given an FHR rating that is listed on the heater's yellow EnergyGuide label. Ideally, find a water heater that matches the FHR you calculated for your family and home. If your number doesn’t match anything on the market, find a water heat that meets your FHR without going below it.