Heat Pump Operating Costs in Cold Weather: What Techs Need to Tell Customers

You’ve probably gotten that service call: Customer bought a heat pump last year, loved it through fall, and now they’re staring at a heating bill that makes their mortgage payment look reasonable. “This thing is broken,” they say. “It has to be.”

Most of the time, it’s not broken. It’s doing exactly what physics says it should do. The problem is nobody explained what that means for their wallet.

Here’s how to have that conversation without losing a customer or making promises you can’t keep.

The COP Reality Check

Coefficient of Performance (COP) is heat delivered divided by electricity consumed. COP 3.0 means 3 units of heat for every 1 unit of electricity, or 300% “efficiency” compared to resistance heat at COP 1.0.¹

But your customer isn’t calling at 47°F. They’re calling at 5°F with “AUX” lit up. Here’s what actually happens:

Important distinction: These are point COP ratings at specific temperatures. Seasonal COP (what actually determines bills) runs 2.0-2.5 for most installations because it accounts for part-load operation, defrost cycles, and temperature variation across the heating season.

Cold climate units meeting the NEEP specification must maintain COP of at least 1.75 at 5°F.² That’s still nearly double the efficiency of electric resistance heat, but it’s half what it was at 47°F.

The key insight most techs miss: inverter-driven heat pumps achieve their highest COP at minimum compressor speed, not at rated capacity.³ A Fujitsu at 5°F might show COP 2.25 at maximum speed but COP 4.0+ at minimum. Since systems operate at part-load most of the time, real-world performance often beats the ratings.

Below 32°F with humidity present, defrost cycles can reduce effective efficiency by 5-15%, particularly in coastal or humid climates.

For more on how heat pump components work together during these temperature swings, check out our guide on bi-flow TXVs in heat pumps.

The Balance Point Explained

The balance point is where heat pump capacity equals building heat loss. Below this temperature, supplemental heat kicks in.⁴ Actual balance point depends on home load calculation (Manual J) and equipment capacity curves, not just equipment type.

Traditional calculations assumed fixed-capacity equipment. Inverter systems change everything by modulating from 20-25% minimum to 100-140% maximum capacity, creating a "soft" transition rather than a hard cutover.⁵

What techs should verify on every call:

• Auxiliary heat lockout temperature: Many systems ship with conservative 35-40°F defaults. If the equipment is a cold climate unit rated to 5°F, that lockout should be much lower.
• Temperature differential setting: Too narrow causes excessive aux heat calls.
• Emergency vs. auxiliary heat mode: Confirm the customer understands the difference and hasn't accidentally locked the system into emergency mode.

Understanding how the reversing valve directs refrigerant flow helps explain why balance points matter differently in heating versus cooling modes.

The Real Cost Comparison

Here's where it gets uncomfortable. The honest answer: it depends.

Current US average rates (2025): electricity at 17.27¢/kWh, natural gas at $1.64/therm.⁶ At these rates, heat pumps need COP around 3.0 to match a 95% efficient furnace.

Regional variation is massive:

In cheap gas regions, don't oversell heat pump economics. Be straight: "Your heat pump will cost more than gas during the coldest months. Where it shines is cooling season and shoulder months." That honesty builds more trust than any sales pitch.

For oil or propane customers? Different story entirely. Heat pumps typically cut operating costs 60-70%.⁷ That's a slam dunk.

The Auxiliary Heat Trap

This is where bills really blow up.

Heat pump normal operation: 3-5 kW. With auxiliary strips engaged: 10-20 kW.⁸ That's 3-5× the electricity per hour.

Common pattern: homeowner wakes cold, bumps thermostat from 68°F to 72°F. Thermostat calls for rapid recovery, fires aux heat. Now they're paying strip heat prices for 45 minutes.

The fix requires customer education:

Set it and forget it. Heat pumps work best with minimal temperature swings. A 2°F setback overnight is fine. An 8°F setback defeats the whole purpose.

If you're diagnosing heat pump performance issues, always check the auxiliary heat runtime before blaming the equipment. I've seen systems flagged as "failing" that were actually running perfect compressor efficiency with aux heat engaged 6 hours a day because of thermostat settings.

Before you head to that "my bill tripled" call, Property.com's "Know Before You Go" tool shows you the home's equipment history, permit records, and past service work. Knowing whether you're walking into a 2-year-old cold climate unit or a 15-year-old standard system changes the conversation completely. No more surprises, better diagnosis, faster trust-building.

The Customer Conversation

When a customer calls about high bills, get curious, not defensive.

Ask first:

• What's your electricity rate? (Most don't know.)
• What thermostat settings are you using?
• How often do you adjust the temperature?
• Is "AUX" showing on the display?

Explain it simply: "Heat pumps are efficient, but efficiency drops as it gets colder. At 40 degrees, you're getting 3 units of heat per unit of electricity. At 10 degrees, maybe 2. Still better than baseboard, but not as good as mild weather."

Set realistic expectations: "Your January bill will always beat your October bill. That's physics. But let's check your settings to minimize auxiliary heat usage."

For more on proper system selection and installation considerations for heat pumps, that article covers the upfront decisions that prevent these calls.

When to Recommend Alternatives

Sometimes the honest answer is that a heat pump isn't the right primary source:

• Cheap gas under $1.00/therm: Dual fuel makes sense. Heat pump to 25-30°F, gas below that.
• Balance point too high: If aux runs constantly below 35°F on equipment rated for 5°F, it's likely undersized.
• Customer won't adjust behavior: Some people do 10°F thermostat swings no matter what. Gas furnaces are more forgiving.

The Bottom Line

Techs who can explain heat pump economics build trust and prevent callbacks. The goal isn't selling anything. It's honest information that helps customers make smart decisions.

Sometimes that means telling them their heat pump is working perfectly despite a high bill. Sometimes it means recommending they add gas backup.

Either way, you've positioned yourself as the expert who tells the truth. That's worth more than any single sale.