When To Upsize a Water Heater | Ask This Old House

In this video, This Old House plumbing and heating expert Richard Trethewey diagnoses and solves a homeowner’s lack of hot water.

Cold showers aren’t for everyone. When a homeowner decided to do something about her distinct lack of hot water, she called upon the Ask This Old House team for help. Richard Trethewey, our resident plumbing and heating expert, answered the call and took us on a road trip to stop an undersized water heater from ruining the homeowner’s showers.

Troubleshooting Hot Water Problems
If you’re running out of hot water during your showers, the first thing to determine is whether the water heater works appropriately. Here’s the test:
• Inspect your water heater and determine what the total gallonage is.
• Turn the shower faucet to the hot water setting, and place a bucket with a 1-gallon mark under the shower head.
• Time how many seconds it takes before the bucket has been filled to the 1-gallon mark. Divide the number 60 by the total seconds to determine the GPM.
• Let the water heater refill and reheat the tank.
• Set the shower to normal showering temperature and time how long it takes to start getting cold.

Multiply the GPM by the minutes it takes to get cold. The number should be 65 to 70 of the water heater’s total size. If that is the case, the water heater is working properly—it’s just too small. If that’s not the case, the water heater might need to be replaced.

A Hybrid Water Heater May Be the Best Solution
Upgrading to a larger water heater doesn’t necessarily mean more energy consumption. Hybrid water heaters exist, combining the age-old technology of electrical elements and built-in heat pumps that remove and resume the heat energy from the space. This allows them to run for a fraction of the cost of a traditional water heater while providing more hot water.

Are They Expensive?
Hybrid water heaters are more expensive to purchase than traditional water heaters. However, they’re less expensive to operate. There are also many rebates from states and the federal government to move to more efficient, more economically-friendly appliances. There are potentially thousands of dollars in rebates available, making these water heaters affordable.

Where to find it?

About Ask This Old House TV:
From the makers of This Old House, America’s first and most trusted home improvement show, Ask This Old House answers the steady stream of home improvement questions asked by viewers across the United States. Covering topics from landscaping to electrical to HVAC and plumbing to painting and more. Ask This Old House features the experts from This Old House, including general contractor Tom Silva, plumbing and heating expert Richard Trethewey, landscape contractor Jenn Nawada, master carpenter Norm Abram, and host Kevin O’Connor. ASK This Old House helps you protect and preserve your greatest investment—your home.

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When To Upsize a Water Heater | Ask This Old House

[CZ-kzug]

This old house is one of the only shows that stayed humble. Thanks.

[howtodoitdude]

These are the only guys I trust on YouTube for home repairs.

[Pitbullgotti]

Do I need a new water heater? No; Did I watch the entire video? Yes.

[ytadmin]

"What?! No Sharkbite?! What a hack job!" I'm kidding. If I ever saw Richard roll up to my house to replace my water heater, I would be humbled to be in the presence of greatness.

[curtismmichaels]

He's got "favorite Uncle" energy, on top of knowing what he's doing.

[KoiBoy]

Installed the 40g version this fall when power bills were climbing, it was one of our highest energy guzzlers in the house. After install, power consumption for the month dropped 300kwh. Upgrade will pay for itself in electrical savings very fast and over the life it will save enough beyond that to pay for the next unit as well. Great systems and can't wait until the summer heat has it working even more efficient.

[knuteeriksen]

Many manufacturers make a tempering valve that allows you to increase the temperature of the water heater and safely mix it at the outlet to deliver more hot water with a smaller tank ….

[bater]

Big fan of Richard, but I put one of these in my mom's house the the installation instructions clearly call for a flexible (PEX or Braided Stainless ) connection for the water lines since the heat pump vibrates.

[kevinclayton]

I have this same water heater and I like it alot. The dehumidifying effect during the summer months is really beneficial. I also definitely noticed a difference in energy consumption. However, I do change it to full electric mode during cold winter months. The thing is like running an air conditioner in my basement and that is about as fun as you can imagine it might be.

[jaredboice]

Is my hot water tank running fine? Absolutely….am I going to get one of those new tanks with a heat pump because of Richard? YES

[GregsWorkshopOregon]

We have an older version of that water heater, 5 years and still going strong. Lowered our electricity bill noticeably when we put it in (although I don’t remember the exact amount).

[sjpropertyservices]

J installed a 60 gallon hybrid heat pump water heater 3 years ago. It replaced an electric water heater which had failed. Rather than replacing the electric water heater the previous owner decided to get the domestic hot water directly from the boiler. This was an expensive way to get our not water. The hybrid heat pump water heater has worked very well and has always worked on tge heat pump mode. The only downside is the cool air it produces which is dumped into the mechanical room where it is located. We received a very substantial rebate for the purchase of the new water heater which made the final price comparable to an electric water heater of the same size. Added benefit of the hybrid heat pump water heater is it helps dehumidifier the mechanical room during warmer months.

[JimDean]

I think my first effort would have been turning up the thermostat on the water heater. If you're starting off with hotter water you're going to use less of it during the shower. It's a new shower so it's got a mixing valve so you shouldn't get scalded. Obviously if they have small children that might not work but it's where I would start. That said what he did may have been the best answer overall because there might be things that weren't in the show that we aren't aware of

[billconnelly]

NICE JOB. RICH IS THE MAN WITH THE PLAN.👍👍👍

[camerond]

Hot water heater has a reduction in costs, but up here in cold Canada your heater will be running more to offset the heat your taking for the hot water heater as that room now will be significantly colder all year round. Still a great show, and they have remained the same today as they were 30 years this is good, stay humble.

[valenzaplumbing]

Great video, but measuring the capacity of the previous tank confused me. Richard used the 70% rule and claimed that a 40 gallon tank really only provides 30 gallons of hot water, but the “first hour capacity” of tank type water heaters is usually 20% more than the tanks size. So a 40 gallon tank would actually provide almost 50 gallons of hot water in the first hour of use once the tank is completely heated.

Also, that’s assuming the water is being used at 120 degrees. No one showers at that temperature. If you mix cold water to decrease the temperature to normal showering temps, you’ll gain even more capacity. Furthermore, if you raised the thermostat temp to 130*F, you’d gain even more.

To save the customer a lot of money, he could have installed a TMV and ran the heater at 160*F, then mixed it down to 120*F, upping the capacity of a 40 gallon tank substantially.

[lockabar]

I understand there are now three heat sources but by your math how is an extra 7 gallons of water going to help? That should only add just under 3 more minutes of shower time, or did I miss something? That seems like a big expense for so little return. Although I understand it'll pay off eventually but not many have such upfront finances to get started.

[chrisbarnes]

I have a 40 gallon electric tank with two elements and it works well for two people, it’s quite, simple and works. My previous tank that was in the house when we bought it was a 50 gallon gas water heater that was 12 years old, gas has a faster recovery but uses non renewable energy.

[brucebradsher]

Great video Richard! Would one of these work where the water heater is in a closet like space instead of a mechanical room? Looks like it would need air flow in a big enough area for the heat pump to work.

[RegularJoes]

For upsizing, check the 1st hour rating requirement for the house, it's based off of number of bedrooms and bathrooms. Heat pump wayer heaters are a lot more efficient if you duct the exhaust to the exterior, the comdensor will work twice as hard trying to heat the extremely cold air its sucking in from the exhaust. Also you'd want a bonding jumper on your metal water lines for shock protection.