What Size Water Heater Do I Need?

Posted by Chris Kauffman
| July 2016

The Right Size Hot Propane Water Heater Will Mean More Efficiency 

Many homeowners ask: What size water heater do I need for my family? Is mine working at its peak efficiency?

As life circumstances change, the size of your propane hot water heater will change with them. Growing families need more hot water, as does anyone who invites guests over frequently.

Cold temperatures can mean water takes longer to heat, so a quality heater can be helpful in the winter, too.

First: Traditional vs. Tankless

When it comes to hot water heaters, you have the option of a traditional tank or a tankless model. Either one can meet your needs, but tankless heaters are more efficient. The greatest efficiency gain is actually seen for those who use the least water – 41 gallons or less each day.

At higher water usage, the differences are less noticeable.

Tankless heaters take up less space, but conventional heater models tend to be less expensive to buy and install. When all is said and done, it’s down to personal preference.

No matter what model you favor, though, there’s one key question you have to answer:

Just what size of propane hot water heater is best for my house?

Size is the main factor in whether you’ll have enough hot water at a reasonable cost.

The Hot Water "Two-Step": Picking the Right Size for Your Propane Hot Water Heater

A propane hot water heater is a good choice for a satisfying, long-lasting purchase.

Propane is a safe, clean-burning, efficient fuel that saves money.

Still, there’s a basic rule for any new appliance: Cutting cost of ownership usually means getting the smallest, most efficient item that meets your daily needs. That’s true no matter if you’re looking at a conventional propane hot water heater or a tankless model.

Why not go with the biggest you can afford? A few reasons:

  • A bigger tank will generally take longer to heat the water you need.
  • You’ll end up spending extra by heating more water than you'll use.
  • You could still run out of hot water if you overestimate your tank.

Luckily, it’s not too hard to get a good idea what size heater is best for you.

Take these two easy steps to find an efficient choice.

Step One: Figure Out the Water Heater’s First Hour Rating

The big factor in day-to-day water heater performance is first hour rating. It’s simply how much hot water your heater provides in an hour. The tank capacity, fuel source, and fuel source size all have an impact.

Here’s how you calculate first hour rating: Tank Capacity x .70 + Recovery

You can get this info from the top left corner of an appliance’s Energy Guide label. The first hour rating should be 1-2 gallons higher than your peak hot water usage.

Our previous post will help you calculate peak hot water use. It’s easy!

Step Two: Review Common Tank Sizes

Figuring out how much hot water you usually use will help you be more confident in your choice. Even if you don’t work through the math around first hour ratings and peak usage, though, you can still make a rough estimate of your needs.

Propane hot water heaters each have a certain gas capacity. Common sizes are:

100 Gallons

100-gallon heaters are great for large families with heavy hot water usage. If you have five or more people who shower daily, do laundry at least once a week, and use hot water in the kitchen, a big tank will help reduce conflict – no one wants to run out!

75 Gallons

A 75-gallon water heater is a good pick for a couple with two growing children – high usage with most family members taking at least one shower or bath daily. With this size, you’ll still be able to handle multiple loads of laundry as needed.

50 Gallons

A 50-gallon heater is a good all-around choice for a couple or threesome with moderate-to-high hot water needs. You might have to ration a little more carefully if you invite a guest, of course.

40 Gallons & Below

40 gallons can be sufficient for a couple that focuses on conserving water. 30 gallons will meet the needs of most individuals. The small tank size means water will heat up quickly as needed.

Consider Sizing Up As Your Needs Grow

If you’re not quite sure what size you need, you think you might buy a bigger washer or expand your bathroom, or your family size could change over the next 12 months, consider sizing up by a small amount. When it comes to hot water, it's better to have a little more than a little less!

New propane hot water heater installation by Kauffman Gas

Chris Kauffman

About the Author

Chris Kauffman

Chris is the Vice President of Kauffman Gas. He is the fourth generation of Kauffmans involved in the daily operations of Kauffman Gas. He helps lead the team in delivering propane gas and top quality service to customers in Chester County, Lancaster County and parts of Delaware County, Pennsylvania.