Hot Water, Cool Savings

Almost every type of water heater now offers improved efficiency—even that dinosaur, the storage-tank heater. Conventional water heaters consume as much as 20 percent of your home’s energy budget. New federal energy mandates now require greater efficiency for nearly all residential heaters, regardless of fuel. While most tankless systems already exceed the new standards, others are catching up, especially condensing and hybrid water heaters.

The size of the house, the number of people in the household, the type of power available (gas or electric, for example), and climate considerations all have a bearing on heating options for hot water. That said, the most important factor in choosing a new heater is the firsthour rating (FHR) for storage-tank water heaters and the gallons-per-minute rating (GPM) for tankless water heaters.

In essence, these ratings tell you how quickly you’ll run out of hot water when multiple users are draining the taps.

A professional can help you estimate what FHR or GPM your household needs. For a storage unit, you’ll also need to know the recovery rate—how fast the heater can replenish water as it’s drawn from the tank. In most cases, this will depend on the burner size (in BTUs) and heat-transfer efficiency.

Another important consideration is the energy factor (EF), a measure of the amount of hot water produced per unit of fuel consumed over a typical day. While a high EF is desirable, it doesn’t necessarily mean that the option with the highest EF will be most cost efficient. That will depend on your climate and how and when you typically use hot water. For more information on estimating costs and efficiency, see energy.gov/energysaver/ selecting-new-water-heater.