Residential Comfort & Energy Efficiency

Written by Eric Gans
I have completed over 2000 Home Performance with ENERGY STAR® home energy audits in Maryland, and I like to write about my experiences.

 

 

When I pointed a thermal camera at my own boiler, I wasn't expecting a surprise.

The pipes feeding my domestic hot water system were over 145°F on a mild spring day—even though there was no need for space heating.

For years, my home used an oil boiler to provide both space heating and domestic hot water. It worked reliably, but after looking at it through the lens of a thermal camera, I discovered something I had never fully appreciated:

My boiler wasn't just heating water—it was heating my basement.

As a certified energy auditor, I spend a lot of time helping homeowners understand how heat moves through a house. This time, I decided to turn the thermal camera on my own mechanical room.

What I found completely changed how I looked at domestic hot water.
 

The Hidden Heat Source Most Homeowners Never Think About

When most people think about a water heater, they think about hot showers.

They don't think about what happens between hot showers.

In my case, the boiler, storage tank, and dozens of feet of copper piping remained hot throughout the day so they would be ready whenever someone turned on a faucet.

That means the system was constantly releasing heat into the basement—even during the warmer months when there was no need for space heating.
 

 

 

The thermal camera showed:

• Boiler temperatures exceeding 170°F

• Copper piping approaching 185°F

• Large sections of the mechanical room were acting like radiators

Every bit of that heat eventually became heat inside the house.
 

The Thermal Camera Changed My Perspective

I've recommended heat pump water heaters for years because of their efficiency and lower operating costs. But pointing a thermal camera at my own mechanical room taught me something I hadn't fully appreciated.

The biggest difference wasn't just the energy savings—it was the complete change in the space's thermal behavior.

Instead of seeing a boiler, storage tank, and dozens of feet of hot piping radiating heat into the basement, I saw a mechanical room that was much closer to the surrounding air temperature.

The thermal images revealed something most homeowners never notice: a domestic hot water system doesn't just affect your utility bills—it also changes how heat moves throughout your home.

Why This Matters During the Summer

In the winter, some of this heat isn't necessarily wasted because your home needs heating.

But during spring and summer, it's a different story.

In some cases, where the domestic usage is tied to the boiler, it continues to maintain hot water, which means:

• Hot pipes continue radiating heat.

• The storage tank continues losing heat.

• The boiler jacket continues giving off heat.

Your air conditioner eventually has to remove that heat from the house.

In other words, your water heating system may be making your cooling system work harder.
 

 

A Water Heater Is Part of Your Home's Comfort System

Most homeowners think of a water heater as an appliance that simply provides hot water.

From a building science perspective, it's much more than that.

Every appliance that produces, moves, or removes heat influences the comfort and efficiency of the entire house. A traditional boiler-fired water heater introduces heat into the surrounding space. A heat pump water heater removes heat from that same space while producing hot water.

That means your choice of water heater doesn't just affect energy costs—it can influence basement temperatures, humidity levels, and even how hard your air conditioning system has to work during the cooling season.

I didn't simply replace one water heater with another.

I changed the direction that heat moves through my house.
 

Heat Doesn't Disappear—It Has to Go Somewhere

One of the first principles of building science is that heat doesn't simply disappear. It always moves from one place to another.

With my old boiler-fired water heating system, some of the heat produced by burning fuel went into the domestic hot water where it belonged. But not all of it. The boiler jacket, storage tank, and long runs of uninsulated copper piping continuously released heat into the surrounding basement.

That heat wasn't "lost"—it simply became unwanted heat inside the house.

The heat pump water heater completely changes that equation. Instead of creating heat and allowing some of it to escape into the room, it removes heat from the surrounding air and transfers it into the water stored in the tank.

The result is the same hot shower, but a completely different path for the heat to travel.
 

Enter the Heat Pump Water Heater

Rather than creating heat, a heat pump water heater works like a small air conditioner.

Instead of generating heat directly, it transfers heat from the surrounding air to the water stored in the tank.

That one difference completely changes the room's thermal behavior.

After installing my heat pump water heater, I repeated the thermal imaging under similar conditions.

The difference was dramatic.

  

The bright, glowing boiler piping was gone.

Instead of multiple pieces of equipment operating well above room temperature, the mechanical room became remarkably uniform in temperature.

The heat pump water heater wasn't filling the basement with hot surfaces—it was removing heat from the air.
 

An Unexpected Comfort Benefit

Lower utility bills were expected.

A cooler basement was an unexpected bonus.

Every time the heat pump water heater runs, it removes heat from the surrounding air while producing hot water.

It also removes moisture as condensation, providing a mild dehumidifying effect.

That means one appliance is doing three jobs:

• Heating your water

• Cooling the surrounding air

• Reducing humidity

It's a combination that conventional boilers and standard electric water heaters simply can't provide.
 

What About Winter?

One question I often hear is:

"Doesn't the heat pump water heater steal heat from the house in the winter?"

Technically, yes—it moves heat from the surrounding air into the water.

But in homes like mine with a boiler, there's another interesting interaction.

The boiler naturally gives off heat through its jacket and piping whenever it's operating for space heating.

Instead of letting all that heat simply dissipate into the basement, the heat pump water heater can capture some of it and convert it into domestic hot water.

It's an elegant example of one system benefiting from another system's unavoidable losses.
 

My Home Energy Audit Predicted Significant Savings

Before making the upgrade, I modeled my home using approved Home Performance energy modeling software.

The projected results were impressive.

 

The model projected:

• 84.1% reduction in water heating energy

• 123 fewer gallons of heating oil consumed annually

• Approximately $481 per year in water heating cost savings

While every home is different, these projections illustrate why heat pump water heaters have become one of the most impactful energy upgrades available for many homeowners.
 

Maryland Homeowners Have Another Reason to Consider One

If you're a homeowner served by BGE or Pepco, replacing an aging oil, propane, or natural gas water heater with an ENERGY STAR® heat pump water heater may be more attractive than ever.

Recent updates to Maryland's Home Performance with ENERGY STAR® (HPwES) program now recognize heat pump water heaters as an eligible electrification upgrade. When included as part of a comprehensive Home Performance project, electrification measures can increase the program's incentive cap to 75% of the project cost, up to $15,000, depending on the improvements being completed and overall project eligibility.

For many homeowners, this means the cost of installing a heat pump water heater can be significantly offset when it's incorporated into a whole-home energy improvement plan rather than treated as a standalone appliance replacement.

That's one of the reasons I encourage homeowners to start with a professional energy audit. Instead of replacing equipment one piece at a time, an audit helps identify which upgrades work together to improve comfort, reduce energy use, and maximize available incentives.
 

Is a Heat Pump Water Heater Right for Every Home?

Not necessarily.

Like any building science upgrade, context matters.

A heat pump water heater performs best when:

• It has adequate surrounding air volume.

• The installation location can benefit from slight cooling and dehumidification.

• The home has sufficient electrical service.

• The homeowner is looking for long-term operating savings rather than simply the lowest upfront cost.

This is one reason I always recommend starting with a professional home energy audit instead of making decisions based on a single appliance.
 

Is a Heat Pump Water Heater Right for Your Home?

Like most building science questions, the answer depends on the house.

This type of upgrade is often worth exploring if you:

• Have an oil, propane, or natural gas water heater that's nearing the end of its life.

• Have a boiler that also provides domestic hot water, especially if it stays warm throughout the summer.

• Want to reduce energy costs without sacrificing hot water performance.

• Have an unfinished basement, utility room, or mechanical space where the slight cooling and dehumidification benefits can be an advantage.

• Are already planning energy improvements through BGE or Pepco's Home Performance with ENERGY STAR® program and want to maximize available incentives (Maryland).

On the other hand, a heat pump water heater isn't automatically the right choice for every home. Installation location, available space, electrical capacity, hot water demand, and your home's overall heating system all play a role in determining whether it's the best solution.

That's why I encourage homeowners to start with a comprehensive energy audit rather than focusing on a single piece of equipment. Looking at the house as a complete system allows you to prioritize the upgrades that will have the greatest impact on comfort, efficiency, and long-term value.
 

Final Thoughts

When I installed my heat pump water heater, I expected lower energy bills.

I didn't expect my thermal camera to reveal such a dramatic change in how heat moved through my basement.

The glowing boiler, storage tank, and hot copper piping were replaced with a system that quietly transfers heat rather than constantly radiating it.

For homeowners replacing an aging boiler-fired water heating system, this upgrade isn't just about efficiency.

It's about changing the way your house manages heat.

And once you see the difference through a thermal camera, it's difficult to unsee it.