What Size Water Heater Do I Need?

Water heaters are a great source of comfort. Especially when you use water appliances a lot in your daily routine, you need a constant hot water supply.

Water heaters are cost-effective and easy to maintain — Life can be difficult without them. Are you planning to buy one? Or are you facing problems with your current heater?

Is your old heater noisy, or is it leaking? Is it not producing enough warm water? Then it is time to replace it.

If you plan to buy a new one, you must consider some factors before buying the right size that fulfills your family’s needs.



Water Heater Sizes Depending on the Number of People

Here are estimated capacities of water tanks depending on the number of people who will be consuming the water:

  • For 1 to 2 people: 30 to 40 gallons
  • For 2 to 3 people: 40 to 50 gallons
  • For 3 to 4 people: 50 to 60 gallons
  • For more than five people: 60 to 80 gallons

These are just rough estimates, and you cannot only rely on this information when looking for an ideal water heater size.

Therefore, to get a precise estimate, you need to consider various parameters, like how much water you utilize per day and your family’s hot water usage habits.

How to Estimate How Much Water Do I Need?

 In addition to capacity, check the First Hour Rating (FHR) of a tank. The First Hour Rating of a tank means the amount of hot water it produces per hour.

Choose a heater with a suitable FHR depending on the amount of water you use daily. Always opt for a heater that exceeds the number of gallons that you need to run water appliances simultaneously in a day.

You can use the following figures to calculate the peak hour of water consumption to estimate an ideal FHR:

  • For Bathing (Per person): 15 gallons
  • For washing hair (Per person): 5 gallons
  • For washing hands (Per person): 1.5 gallons
  • Shaving (Per person):2 gallons
  • Doing the dishes: 5 gallons
  • Running washing machine: 25 gallons

FHR determines the efficiency and ability to produce maximum hot water at the busiest point of the day. 

Hot Water Usage Habits

The estimated figures of tank capacities needed for a particular number of people may not always be correct. A family of 5 people may consume only 40 gallons of water.

And a family of 2 to 3 people may need a 50 to 60 gallons heater to fulfill their requirements. It all depends on the water usage habits of the family.

Suppose you run 3 to 4 water appliances simultaneously, such as a dishwasher, washing machine, faucets, and showers. In that case, you need a high-capacity water heater to ensure that you do not run out of enough hot water.

Which Water Heater Should I Buy?

Here are some of the steps to follow to determine the size of the water heater that you should buy:

1. Estimate Peak Water Usage

Peak water usage means the time of the day when you are consuming the most amount of water. You can make a list of appliances you use with the water amount needed in gallons-per-minute (GPM).

For example, if the water needed for taking a shower is 3 GPM, and the washing machine consumes 4 GPM, and you are doing both simultaneously, you need a water heater with a 6 GPM flow rate.

2. Estimate the Temperature of Water Entering Your House

You can turn on the faucet and use a thermometer to check the temperature of the incoming water. Then subtract the temperature from 110 degrees Fahrenheit.

The result is the temperature rise required. All water tanks have charts that tell the flow of hot water at various temperatures.

3. Tankless Heater For Less Space

If you lack space for a large water heater to fit in, opt for a tankless water heater that is wall-hung and manufactured to fit in small spaces.

They do not require any storage. Tankless heaters heat water directly that enters the house. The cold water enters the unit through a pipe.

You do not need to wait for the water to heat up as tankless heaters provide hot water at a constant rate. 

Final Thoughts

Before buying a water heater, determine the water usage habits of your family and calculate the FHR needed. All water heaters have an FHR in their description.

If you decide to buy a tankless heater instead of a traditional one, different factors are considered before buying.

The major difference between the two is that a traditional one heats and stores water while the tankless one heats water directly entering your house.

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