Small households of two people need a tankless heater with a flow rate of 6 to 8 GPM, while a larger household of four people requires a flow rate of about 8 to 10 GPM. Remember to factor in temperature rise when deciding how big of a tankless water heater you need for your household.
Proper sizing is important prior to select and installing a tankless, but in general the average rules for sizing the correct water heater for a household are roughly: 3.5 GPM for 1-2 fixtures simultaneously. 5 GPM for 2-3 fixtures simultaneously. 7 GPM for 3-4 fixtures simultaneously.
You can go with a small tank and a small tankless water heater at the same time. You install this as a single device (1.5 gal per minute) tankless water heater with the output going to the tank and the tank feeding your household. If you need a lot of hot water quickly both water heaters run at the same time.
But on average, different family sizes require the following sizes of tankless water heaters: Family of 2 — 6-8 GPM. Family of 3 — 7-9 GPM. Family of 4 — 8-10 GPM.
A 50-gallon water heater should be replaced with a tankless system with a 10 GPM flow rate just to be safe. Selecting the right flow rate ensures you won't experience cold showers or excessive energy costs. Proper sizing optimizes performance, providing hot water on demand without unnecessary waste.
The federal tax credit for tankless water heaters can lead to significant savings for homeowners. Eligible tankless gas water heaters must have an ENERGY STAR certification and a UEF of greater than 0.95. Homeowners can claim up to $3,200 in tax credits for eligible home improvements in a single year.
1 to 2 People: 30 – 40 Gallons. 2 to 3 People – 40 – 50 Gallons. 3 to 4 People: 50 – 60 Gallons.
The average American family of four uses 400 gallons of water per day. On average, approximately 70 percent of that water is used indoors, with the bathroom being the largest consumer (a toilet alone can use 27 percent!).
Advantages and Disadvantages of Tankless Water Heaters
The initial cost of a tankless water heater is greater than that of a conventional storage water heater, but tankless water heaters will typically last longer and have lower operating and energy costs, which could offset their higher purchase price.
Sizing Tankless or Demand-Type Water Heaters
List the number of hot water devices you expect to use at any one time. Add up their flow rates (gallons per minute). This is the desired flow rate you'll want for the demand water heater.
Additional Installation Costs
Tankless water heaters are much more complex than traditional hot water tanks. As a result, they require professional installation. If you're switching from a hot water tank to a tankless unit, you will likely need your gas lines rerouted, as well as a larger gas supply line.
Do I need to replace all my home's plumbing if I install a tankless water heater? Rarely is a complete overhaul necessary. However, you may need to upgrade certain sections of your plumbing, particularly those leading into and out of the tankless unit, to ensure proper water flow and volume.
On the other hand, an oversized unit will cost more to purchase and operate than necessary, negating one of the biggest benefits of tankless water heaters—energy efficiency! In short, the tankless water heater size must be just right to meet your expectations.
While you can do it yourself, Monkey Wrench Plumbing, Heating, Air & Electric recommends that you hire a certified technician to install your tankless water heater so that you can get the most out of your investment.
Because tankless water heaters only consume energy when you need hot water, they're more energy efficient, saving you money on water and energy bills.
The cost of a tankless water heater at Home Depot can vary depending on the type and features you choose. Generally, electric tankless water heaters have a lower upfront cost, ranging from $200 to $700, while gas-powered tankless water heaters can cost between $500 and $1,500 or more.
Keep your water heater away from outside elements
If your tankless heater is exposed to extremes weather conditions, it will run a greater risk of premature failure. So, make sure your appliance is away from doors and windows, and never installed in the garage or basement.
What is Average? The water industry estimates that an average person uses 3,000 gallons of water monthly, so a family of 4 would use 12,000 gallons for bathing, cooking, washing, recreation and watering.
Flush Facts
Design improvements have allowed toilets to use 1.28 gallons per flush or less while still providing equal or superior performance. This is 20 percent less water than the current federal standard of 1.6 gallons per flush.
Shower gallons per minute
The average American shower uses 17.2 gallons (65.1 liters) and lasts for 8.2 minutes at average flow rate of 2.1 gallons per minute (gpm) (7.9 lpm).
For a family of four, you will likely need a tankless water heater capable of producing hot water for two to three bathrooms simultaneously. Factor in the temperature rise needed for your desired hot water temperature. Typically, a temperature rise of 70°F is required to achieve a 120°F hot water temperature.
Think about how much hot water your household typically needs. If you live alone or with one other person, a 40-gallon heater might be plenty. But if you have a larger family or need more hot water for back-to-back showers, dishes, and laundry, a 50-gallon heater can make life a lot easier.
50 gallons gives a total of 25 minutes of showering, say 30 we count the recovering capacity, which is about 15 minutes per shower. That seems to be plenty of time for a shower if you ask me. If one person takes a 10 minutes shower (also very reasonable time for a man) the other has 20 minutes left.