When Heat Pumps Struggle to Maintain Temperature (And When That’s Actually Normal)

A heat pump struggling to maintain temperature is not always a problem. During very cold or windy weather, many heat pumps operate continuously and may stay a few degrees below the thermostat setting. This is normal behavior in older or drafty homes. Ongoing temperature loss, weak airflow, or rising electric bills can indicate a real system or insulation issue that should be evaluated by a professional.

You set the thermostat to 70°F. Many Massachusetts homeowners do this expecting the familiar blast of heat they got from older fossil fuel systems.

It’s been sitting at 67°F for hours. That small gap can feel bigger when you know the state’s average residential electricity price sits north of 30 cents per kWh, placing Massachusetts among the nation’s most expensive energy markets, according to federal EIA data.

The heat pump is running. Constantly. Modern air source heat pumps and mini split systems are engineered for steady, energy efficient operation, but the constant hum can still feel unsettling if you are new to the technology.

Now you are staring at the wall wondering whether something is broken, whether this system was a mistake, or whether everyone who told you heat pumps work great in Massachusetts forgot to mention this part. You might even be questioning the wisdom of your heat pump installation, the promised Mass Save rebates, or the advertised tax credits that helped you choose a clean energy path in the first place.

Here is the truth most homeowners never hear clearly.

Sometimes a heat pump struggling to maintain temperature is normal. Other times it is a real problem. The difference matters. Confusing the two leads to unnecessary panic, wasted money, or the wrong fix. Getting it right protects your wallet from higher energy costs, reduces heating bills, and helps maintain indoor air quality with fewer combustion byproducts.

According to Mass Save, “Today’s cold climate heat pumps are two to three times as efficient as a boiler or furnace and many provide efficient heat at outdoor temperatures as low as minus fifteen degrees Fahrenheit,” while delivering cleaner, safer, and more flexible comfort throughout the year.

Let’s walk through what is actually happening.

The Big Misunderstanding About Heat Pumps and Thermostats

Most Massachusetts homeowners grew up with oil boilers, gas furnaces, or steam heat. Those systems all work the same way. They blast heat hard, overshoot the set temperature, shut off, then wait until the house cools down again.

Heat pumps do not work like that.

Instead of creating heat through combustion, a modern air source unit moves heat from outside to inside. That is why heat pumps are considered highly efficient heating and cooling equipment.

As ENERGY STAR explains, “Because heat pumps move heat rather than converting it from fuel, an air source heat pump can deliver up to three times more heat energy to a home than the electrical energy it consumes.” That gentler supply air temperature is a sign of efficiency, not failure.

A cold climate heat pump is designed to deliver steady, consistent heat rather than aggressive bursts. It ramps up slowly, runs longer, and focuses on holding the home at temperature instead of constantly overshooting it. This operating style is central to heat pump technology and is one reason climate rated systems earn high efficiency ratings and favorable utility rates from providers like National Grid and Eversource.

That difference alone explains much of what people interpret as struggling. If you are used to scorching hot air pouring out of a furnace vent, the gentler heat from a pump can feel underwhelming even though it is providing cost effective, efficient heating.

If your thermostat reads 68°F instead of 70°F on a very cold day, that does not automatically mean the system is failing. In many cases, it means the heat pump is working exactly as designed. It is maintaining comfort without wasting electricity, preserving efficiency, and controlling long term energy costs.

When It Is Completely Normal for a Heat Pump to Fall a Few Degrees Short

There are situations where a heat pump falling behind the set temperature is expected, especially in Massachusetts. These conditions are factored into the design of most cold climate systems and are accounted for in Mass Save heat load calculations.

Cold snaps and balance points

Every heat pump has a point where heat loss from the house starts to catch up with heat production. On especially cold or windy days, the system may hover a few degrees below setpoint while running continuously.

This is exactly why many heat pump owners pair their equipment with electric resistance or dual fuel backup. It preserves comfort during extreme cold without sacrificing year round efficiency.

This is not a breakdown. It is physics. The laws of thermodynamics do not bend, but advances in heat pump technology and smart controls allow modern systems to deliver reliable heat well below freezing.

Older and leakier homes

Colonials, capes, triple deckers, and homes built before 1960 lose heat faster than most homeowners realize. Even a perfectly installed heat pump can struggle to overcome drafts, poor insulation, and unsealed attic bypasses.

Weatherization through programs like Mass Save can dramatically improve energy efficiency and indoor comfort while lowering future heating costs.

Large open layouts with limited zoning

One zone attempting to heat a large open space can make it feel like the system is not keeping up even though it is operating at full capacity. Adding additional mini split air handlers or improving zoning design can help balance temperatures and optimize efficiency.

Efficient sizing rather than oversized systems

Properly designed heat pumps are sized closer to actual heat loss rather than being oversized like older boilers. This improves efficiency but also means there is less excess capacity during extreme weather.

The goal is not to waste electricity with oversized equipment. The goal is a balanced system that delivers comfort, efficiency, and long term reliability.

In all of these cases, the system is not broken. It is operating within its design limits. Understanding those limits helps homeowners avoid unnecessary service calls and focus on real performance issues.

When Struggling Is Actually a Red Flag

This is where homeowners should pay close attention.

A heat pump should not be losing ground indefinitely. If indoor temperatures continue to fall, you are no longer seeing normal cold weather behavior. You are dealing with a performance issue that can increase energy costs and compromise comfort.

Warning signs include:

• Indoor temperature continues dropping even though the system runs nonstop

• Supply air feels barely warm rather than moderately warm

• Short cycling instead of steady operation

• Ice buildup on the outdoor unit that does not clear during defrost

• Sharp increases in electric usage with no improvement in comfort
  
  

These are not normal winter characteristics. They point to installation, airflow, control, or equipment problems that need professional evaluation.

The Most Common Reasons Heat Pumps Fail to Keep Up in Massachusetts Homes

After thousands of installations and service calls across more than 160 Massachusetts communities, the same root causes appear repeatedly.

Undersized systems

If a system was installed without a proper heat loss calculation, it may not have enough capacity for the home. ENERGY STAR recommends Manual J calculations to ensure proper sizing and performance.

Poor zoning design

Too few indoor units, poor placement, or mismatched zones can leave parts of the house chronically underheated. Adding heads, adjusting zoning, or integrating ducted air handlers often restores balance.

Insulation and air sealing gaps

Heat pumps move heat. They do not create it. If a home leaks heat faster than the system can replace it, comfort suffers. Insulation upgrades are often the most cost effective way to lower energy bills, and Mass Save rebates can help offset costs.

Thermostat strategy problems

Large temperature setbacks and frequent manual adjustments often slow recovery instead of improving comfort. Smart thermostats designed for heat pump operation help maintain steady output and reduce unnecessary energy use.

Equipment not designed for cold climates

Not all heat pumps are built for New England winters. The U.S. Department of Energy confirms that cold climate heat pumps are designed to perform efficiently at temperatures as low as 5°F. Choosing equipment with the ENERGY STAR Cold Climate label is essential.

For added verification, the Northeast Energy Efficiency Partnerships organization maintains a public Cold Climate Air Source Heat Pump Product List that confirms low temperature performance.

What Homeowners Should Do Before Assuming the System Is Broken

Before assuming you need a repair or replacement, take a moment to check the basics.

Give the system time to stabilize. Heat pumps are not fast reacting systems. Avoid cranking the thermostat aggressively, which can trigger inefficient electric resistance backup. Check filters and airflow. Restricted airflow limits performance.

Make sure the outdoor unit is clear of snow and ice. Look at patterns over several days rather than one cold afternoon.

If the system stays close to the set temperature and remains stable, it is likely doing its job.

When Backup or Hybrid Heat Is the Right Answer

There is a persistent myth that needing backup heat means heat pumps do not work in Massachusetts.

That is not true.

Hybrid systems often provide the best balance of comfort and control. Backup heat supports the system during extreme cold while allowing the heat pump to handle most of the season efficiently.

ENERGY STAR notes that dual fuel systems allow homeowners to switch between energy sources to optimize operating costs and comfort throughout the year.

Electric resistance, oil, or gas backup is not failure. It is redundancy. With smart controls and seasonal heat pump rates through Mass Save, homeowners can fine tune when each system operates to minimize total energy costs.

Unlocking Mass Save Rebates, Bonuses, and Financing

Mass Save currently offers tiered air source heat pump rebates of up to $2,650 per ton, capped at $8,500 for whole home systems. Partial home installations may qualify for lower rebates but still benefit from additional incentives.

Mass Save also offers a $500 weatherization bonus for customers who complete recommended insulation and air sealing within one year of a partial home installation, along with a $500 sizing bonus for systems properly designed to meet the home’s full heating load.

Eligible homeowners may also qualify for a zero percent HEAT Loan of up to $25,000, allowing project costs to be spread out without interest.

The Bottom Line for Massachusetts Homeowners

A heat pump struggling to maintain temperature does not automatically mean something is wrong.

It may be operating within normal limits for a cold climate. It may be compensating for a drafty building envelope. Or it may indicate a system issue that needs correction.

Knowing which situation applies protects your budget, preserves indoor air quality, and ensures you continue to benefit from an efficient heating system.

Not Sure Which One You Are Dealing With?

At Endless Energy, we do not jump straight to replacements. We measure, diagnose, and explain what is actually happening in your home so you can make informed decisions with confidence.

If your heat pump feels like it is working too hard or not keeping up, a performance check can determine whether the behavior is normal or needs attention. Sometimes the fix is as simple as airflow or insulation. Other times a system upgrade, potentially eligible for federal tax credits, is the smarter long term choice.

Endless comfort starts with understanding how your system truly works. Give us a call at 508-794-8590 or self-schedule your heat pump consultation or heat pump service online.

Frequently Asked Questions About Heat Pumps and Temperature Issues

Why does my heat pump run all day in winter?

This is normal. Heat pumps are designed to run for long periods at low power rather than cycling on and off like furnaces or boilers. Continuous operation helps maintain steady indoor temperatures and improves overall efficiency.

Is it normal for my heat pump to stay a few degrees below the thermostat setting?

Yes, especially during very cold or windy days. A heat pump may hover two to three degrees below the set temperature when heat loss from the home matches the system’s output. This does not mean the system is failing.

At what outdoor temperature do heat pumps stop working?

Modern cold climate heat pumps are designed to operate well below freezing. Many continue providing heat at outdoor temperatures as low as minus five to minus fifteen degrees Fahrenheit, though capacity decreases as temperatures drop.

Should I turn the thermostat up higher if my heat pump is not keeping up?

No. Turning the thermostat up aggressively often makes recovery slower and can trigger inefficient electric resistance backup. Heat pumps perform best when set to a steady temperature.

Why does the air from my heat pump feel cooler than furnace air?

Heat pump supply air is typically warmer than room temperature but cooler than furnace air. This is normal and reflects efficient heat transfer rather than a problem with the system.

How do I know if my heat pump is undersized?

If indoor temperatures consistently fall behind during normal winter conditions, not just extreme cold snaps, the system may be undersized. A professional heat loss calculation is the only reliable way to confirm this.

Can poor insulation make my heat pump struggle?

Yes. Heat pumps move heat but do not create it. If your home loses heat quickly due to poor insulation or air leaks, even a properly sized system may struggle to maintain temperature.

Is backup heat a sign that my heat pump failed?

No. Backup heat is often part of a smart system design in Massachusetts. It provides support during extreme cold while allowing the heat pump to handle most heating needs efficiently throughout the season.

Does running my heat pump constantly increase my electric bill?

Not necessarily. Continuous low speed operation is usually more efficient than frequent on off cycling. Large bill increases typically point to heat loss issues, backup heat running too often, or system performance problems.

When should I call a professional about heat pump performance?

You should call a professional if indoor temperatures keep dropping, supply air feels barely warm, the system short cycles, ice builds up and does not clear, or electric usage spikes without improved comfort.