Water heater tank size matters when it comes to heating faster & using less energy
When choosing the right size tank for your water heater, bigger isn’t always better. Matching your water heater capacity to the hot water needs of your family can save you money and make your water heat faster.
While you can choose between a storage tank, tankless water heater, or solar tank, this post will focus on storage tanks as they are found in most households.
Understanding First Hour Rating
The first hour rating is how much hot water your heater can deliver in a single hour. It depends on tank capacity, fuel source, and size of the fuel source.
Tank Capacity x .70 + Recovery = First Hour Rating.
On the Energy Guide label, the first hour rating will be in the top left corner of the label.
Match first hour rating within 1-2 gallons of your peak hour demand.
Peak hour demand is how much hot water your family will use in one hour.
Use this chart to determine peak hour demand:
| Use | Average Gallons of Hot Water Usage | Times per hour | Gallons used in One Hour | ||
|---|---|---|---|---|---|
| Shower/Bath | 20 | x | = | ||
| Shaving | 2 | x | = | ||
| Hand/Face Washing | 2 | x | = | ||
| Hand dishwashing | 2 | x | = | ||
| Food Preparation | 2 | x | = | ||
| Automatic dishwasher | 6 | x | = | ||
| Clothes washer | 7 | x | = | ||
| Total | 20 | x | = |
Higher Energy Factor rating = more efficient tank
The energy factor indicates the efficiency of many home appliances, including water heaters, dishwashers, clothes washers, and clothes dryers. A higher energy factor on your hot water heater means:
- More efficient recovery time(how efficiently heat is transferred to water)
- Lower standby losses (heat loss per hour from stored water)
- Fewer cycling losses (the loss of heat as hot water circulates through tank)
Energy Star rated propane gas water tanks should have an Energy Factor greater than 0.67 for 55 gallon or less tanks, and an Energy Factor greater than 0.77 for 55 gallon or more tanks.
Additional factors that influence size of your water heater
Your family may be classified as higher demand if you have more bathrooms, hot water appliances, or similar shower schedules in your home.
- Household bathroom count
- Schedules of people in the home
- Other Hot Water Appliances
Common gallon capacity required per family-size
| Family Size | Demand | Gallon Capacity Required (for Gas) |
|---|---|---|
| 5 + | High | 75-100 |
| Low | 50 | |
| 3-4 | High | 50-75 |
| Low | 40 | |
| 2-3 | High | 40-50 |
| Low | 40 | |
| 1-2 | High | 40-50 |
| Low | 30 |
FAQs
How do I know what size propane water heater my family needs?
The right size depends on your household’s peak hot water demand.
Calculate your family’s usage using the First Hour Rating (FHR), which combines tank capacity and recovery rate.
Matching your FHR within 1–2 gallons of your peak demand ensures you have enough hot water without wasting energy.
What is the First Hour Rating on a propane water heater?
The First Hour Rating (FHR) measures how many gallons of hot water a heater can deliver in one hour of peak usage.
It’s based on tank capacity and recovery rate. You’ll find the FHR on the Energy Guide label, helping you choose the best tank size for your household.
Are propane water heaters energy efficient?
Yes. Propane water heaters are highly efficient compared to electric models, especially if they are Energy Star rated.
Tanks with an Energy Factor (EF) greater than 0.67 for under 55 gallons—or greater than 0.77 for larger tanks—use less energy, reduce standby losses, and deliver faster recovery times.