Key takeaways:
- Properly sizing a water heater is important because it ensures the new unit meets your household’s needs and can save energy.
- There are rules of thumb to follow based on household size, but you also need to consider your routine.
- This blog takes a closer look at the different numbers to consider, from tank capacity to first-hour rating or recovery rate.
If you’re in the market for a new water heater, you might wonder about what size water heater you need.
In most cases, getting a water heater the same size as the old one is fine, but replacing your water heater is an opportunity to do some research and figure out if you could benefit from an upgrade.
Read on to learn more about water heater sizing and get a better idea of the ideal capacity for your home.
What Size Water Heater Do I Need?
If you’re looking into getting a tank water heater, the first thing you should look at is the capacity in gallons.
As a rule of thumb, you can use these sizing recommendations for your new water heater:
- 1 to 2 people: A 30- to 40-gallon tank is often enough for a small home or apartment with one bathroom and average hot-water use.
- 2 to 3 people: A 40- to 50-gallon tank can work well for a household with one or two bathrooms and typical daily water use.
- 3 to 4 people: A 50- to 75-gallon tank may be a better fit for families with back-to-back showers, regular laundry, and dishwasher use.
- 5 or more people: A 75- to 100-gallon tank may be necessary for larger households with multiple bathrooms and heavier peak-hour demand.
Keep in mind that these are only general recommendations. Your household’s needs for hot water can vary based on how many fixtures you tend to run at the same time.
Tank Water Heater Size: Why You Should Look Beyond Gallon Capacity
Gallon capacity can help you narrow down your options, but you should also consider the space the new water heater will take, the first-hour rating (FHR), the fuel type, and the recovery rate.
Physical Space
Tank water heaters have a diameter of 20 to 30” and can be as tall as 80”. In Middle Tennessee homes, you’ll often find water heaters installed in the basement, utility or laundry room, mechanical closet, attic, or crawlspace-accessible area.
In other words, you may not have a lot of space to install a bigger unit. A good compromise can be to look for a water heater with a tall and narrow design if you’re looking to increase tank capacity without taking up more floor space.
First-Hour Rating (FHR)
A water heater’s first-hour rating tells you how much hot water the appliance can deliver in the first hour you turn the hot water tap on.
A model with a large tank will typically have a higher FHR compared to a smaller tank, but you can find smaller water heaters with a good FHR thanks to their efficient heating element.
Higher FHR can be useful if you’re looking for a water heater that can handle supplying hot water to multiple fixtures at the same time.
Recovery Rate
The recovery rate of a water heater indicates how quickly the appliance can produce more hot water. A higher recovery rate is especially helpful for households with back-to-back showers, frequent laundry, large families, or multiple fixtures running at the same time.
Fuel Type
Water heaters can use gas or electricity. In most cases, it’s best to go with the same fuel type as your old water heater so you don’t have to run a new gas line and venting or install a new electric circuit to power the new water heater.
However, you should know that gas water heaters tend to heat up water faster. Installing a gas water heater can be worth it if you’re looking for a higher FHR and don’t have the floor space for a larger tank.
How to Size a Tankless Water Heater
If you’re thinking about getting a tankless water heater, you’ll need to size this appliance based on two numbers.
Hot-Water Flow Rate
The hot-water flow rate of a tankless water heater, expressed in gallons per minute or GPM, reflects how much hot water the appliance can deliver at any given time. It tells you how quickly it can heat up water, and how many fixtures running at the same time it can handle.
Here are a few sizing recommendations:
- 1 to 2 people with 1 to 2 bathrooms: A unit capable of delivering about 5 to 7 GPM may work for one shower plus a sink or appliance.
- 3 to 4 people with 2 to 3 bathrooms: A unit capable of delivering about 8 to 10 GPM may be a better fit for two showers or a shower and an appliance running at once.
- 5 or more people with 4 or more bathrooms: A system capable of delivering about 9 to 11+ GPM may be needed for several simultaneous showers and other hot-water uses.
For large homes or homes where the layout would require a long pipe run for a single tankless appliance to supply multiple bathrooms, you can look into having two or more tankless water heaters installed. You can also rely on a traditional tank model for your kitchen, laundry room, and main bathroom, and upgrade your guest bathroom with a tankless water heater.
Temperature Rise
Temperature rise is the difference between the cold water entering the appliance and the hot-water temperature you want it to deliver. For instance, a temperature rise of 50°F means you’re heating up water from 70°F to 120°F.
This number is important because some manufacturers might show a higher flow rate, but it’s because they’re testing the water heater with a low temperature rise.
In Middle Tennessee, you also have to consider that the needed temperature rise will be higher in the winter when the water entering your home will be colder.
Do You Need to Increase the Size of Your Water Heater?
If your current water heater consistently struggles to keep up with your household’s hot-water demand, replacing it with the same size may repeat the problem.
Here are some signs you could benefit from sizing up:
- You regularly run out of hot water during the morning or evening rush.
- Your current unit can’t handle back-to-back showers.
- The water temperature drops when you’re using more than one fixture.
- Your bathroom has a larger tub or new high-demand fixture.
- Your routine has changed, you’ve added new fixtures, or your family got bigger.
Get Help Choosing the Right Water Heater With Airstream Services HVAC, Electrical & Plumbing
Airstream Services HVAC, Electrical & Plumbing is a licensed plumber serving Nashville and surrounding communities in Middle Tennessee
If you’re in the market for a new water heater, we can help you figure out the ideal size after asking a few questions and looking at your plumbing setup. After helping you select a water heater, our team can handle the installation and ensure your new unit is set up for dependable hot water in your home.
Call us today at 615-216-5979 or book your water heater consultation online.
FAQ
What size water heater do I need for a family of four?
Many four-person households do well with a 50- to 75-gallon tank water heater. However, the best choice depends on your first-hour rating needs, number of bathrooms, and whether people tend to shower at the same time.
Should I replace my water heater with the same size?
Replacing your water heater with the same size is often fine if it has consistently met your household’s needs. If your family has grown, you added a bathroom, or you frequently run out of hot water, it may be time to size up.
What does first-hour rating mean on a water heater?
First-hour rating is the number of gallons of hot water a fully heated tank can supply during the first hour of use. It includes the hot water stored in the tank and the water the system can heat while you are using it.
How do I size a tankless water heater?
Size a tankless water heater based on your peak hot-water flow rate and required temperature rise. Add the GPM of fixtures that may run at once, then choose a unit that can meet that demand at your home’s incoming-water temperature.
