Tankless Water Heater Gallons Per Minute (GPM) Guidelines

Tankless water heaters are designed to provide homeowners with an unlimited supply of hot water. Each unit is designed to provide a maximum amount of hot water, however, which means some units can be underwhelming when they are at or near capacity for water temperature.

That is why it is important to understand how much water you and your family use before selecting the best tankless water heater for your home. Here are some general guidelines to consider, based on family size.

Water System Planning for Tankless Systems

The average person in the United States uses about 100 gallons of water per day. For a family of 4, that means 400 gallons of consumption is possible. For a family of 6, that means 600 gallons of water are consumed.

In regions where water conservation is required, consumption rates may drop by 50%. That means the family of 6 would use 300 gallons of water instead of 600 gallons.

Certain appliances use a lot of water that a tankless system must support. Here are the biggest water-consuming appliances in the average home.

  • Top-loading washing machines use up to 50 gallons per laundry cycle.
  • Dishwashers use up to 14 gallons per cleaning cycle.
  • Water softeners can use 100 gallons of water per regeneration cycle.
  • Older toilets may use 5-7 gallons per flush.

When shopping for a new tankless water heater, you must combine the use of these appliances with the personal use of hot water.

How Much Water Is Used During Peak Demand?

Your new tankless system must be able to meet your hot water needs during a period of peak demand. That means you must know, with precision, how much hot water is required, per minute, during the times when everyone may have a need.

Now total hot water demand is different than overall water demand. Families should plan on 20% of their water usage to be hot water. For the average family of 4 not conserving water, that would mean a system must support 80 gallons of hot water per day.

A good rule to follow is this: your water heater should be able to supply enough hot water to your home that it can meet daily demand levels within 30 minutes.

For a family requiring 80 gallons of hot water per day, that means the tankless system must be able to operate at 2.67 gallons per minute. For a family of 6 not practicing water conservation, the tankless system would need to support a minimum of 4 gallons of hot water per minute.

That is why many homeowners find themselves underwhelmed by what their new tankless systems provide. If you have a family of 6, but the tankless system only outputs 3 gallons per minute, there is a good chance that the water will be lukewarm, instead of hot, during a peak demand period.

How to Avoid Peak Demand Issues with a Tankless System

There are two ways to avoid peak demand issues that reduce the overall temperature of the hot water you receive: install multiple water heaters or manage your water usage schedule.

At 4 gallons per minute, a tankless system and support one shower and two sinks simultaneously. In some homes, it may be able to support two showers at the same time. You would not want to be running your dishwasher or a hot-water load in your washing machine during this time.

The reverse is also true. If you schedule your laundry chores for specific times, then the household can avoid having a lukewarm shower while the washing machine takes over the hot water system to clean clothes.

For larger families, even when a tight schedule is followed, a mid-range tankless system does not have enough strength to get the job done. That’s why a family of 6, or larger, should look for a system that offers 5-7 gallons per minute of hot water support for best results.

Is a Tankless Water Heater Right for My Home?

Large families may not experience the same benefits of a tankless system as smaller families. There are fewer energy savings available to larger families as well. That means a tank-based system, of 85 gallons or more, may provide a better result than a tankless system with a lower overall initial cost.

Smaller families, however, can experience the benefits of a tankless system right away. Even entry-level systems that offer 2 gallons per minute can supply enough hot water for a shower. With good time management, other uses can be managed to reduce peak demand issues in a budget-friendly way.

Tankless systems are growing in popularity because of their many benefits. Take the time to explore those benefits today and you may find the solution to hot water access you’ve been trying to find.

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Greg Mattson

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