This question is commonly asked by homeowners considering a whole house tankless water heater, and the answer depends on the demand that will be placed on the unit. In many cases, one unit is enough. At other times, more than one whole house tankless water heater will do a better job of insuring a continuous supply of on-demand hot water.

The key to determining whether you will need two units or whether you can get by with one is to compare how much hot water your home typically uses with the hot water producing capacity of the tankless water heaters you are considering for purchase.

To start, consider the outflow capacity of the faucets and appliances in your home. A kitchen faucet or utility faucet flows at the rate of 2.2 gallons per minute. A bathroom faucet also flows at 2.2 g.p.m. Shower heads are the same – 2.2 g.p.m. Keep in mind that these figures represent the maximum flow. If the handle is not opened all the way, the flow will be less.

Appliances like dishwashers or washing machines use more gallons per minute when running, but they run intermittently, so do not present a capacity problem in most cases. Now, if you have a large family that uses multiple hot water feeds at once, add more of these together. Smaller families will have less hot water running at any one time.

When you’ve done the math, peruse the whole house tankless water heaters you are considering to see if there is a unit that will handle the capacity. If so, one is all you need. If not, consider buying a unit with a quick-attach feature, meaning a second unit can be added with little or no additional plumbing. The good news is that most manufacturers of tankless water heaters produce a unit designed to handle the hot water needs of medium to large families.

Learn More at the places below:

Filed under: Articles & Buying Guides