A 3-ton heat pump typically draws 15 to 20 amps during normal heating or cooling, but can spike to 30 to 40 amps during startup or when the backup electric resistance heater kicks in

The exact amperage depends on three things: whether the unit is in heating or cooling mode, whether the compressor is running alone or with the electric backup heater, and the efficiency rating of your specific model. A 3-ton heat pump running its compressor only will draw somewhere in the 15 to 20 amp range on a 240-volt circuit. When the outdoor temperature drops below the heat pump's balance point (usually around 35 to 40 degrees Fahrenheit), the system switches on an electric resistance heater inside the air handler to supplement the heat pump. That backup heater alone can draw 10 to 15 additional amps, pushing total draw to 25 to 35 amps or higher.

The startup surge is real and worth understanding. When the compressor first turns on, it draws what's called inrush current — a temporary spike that can be 2 to 3 times the running amperage. This lasts only a few seconds, but it's why your electrical panel and breaker must be sized to handle it. Your electrician will have already accounted for this when they sized your circuit, but it's the reason a 3-ton heat pump needs a dedicated 40 or 50-amp breaker, not a 20-amp one.

Key Takeaways

  • A 3-ton heat pump compressor alone draws 15 to 20 amps on a 240-volt circuit during normal operation.
  • When the electric backup heater runs in cold weather, total amperage can jump to 30 to 40 amps or higher.
  • Startup inrush current can temporarily spike to 2 to 3 times the running amperage, which is why the breaker must be oversized.
  • Your circuit breaker should be rated for 40 to 50 amps to safely handle both running load and startup surge.
  • If your heat pump trips the breaker repeatedly, the problem is usually the backup heater running too often, not the compressor itself.

Why the backup heater matters more than the compressor

Most homeowners assume the compressor is the power hog, but in cold climates the electric resistance heater is often the bigger draw. The compressor is efficient — it moves heat rather than creating it — so it uses less electricity per unit of heat delivered. The backup heater, by contrast, converts electricity directly to heat at roughly 100 percent efficiency, which sounds good until you realize that direct conversion is power-hungry.

When outdoor temperature drops below your system's balance point, the thermostat automatically switches on the backup heater to keep up with demand. If you live somewhere that regularly hits 30-degree nights, your heat pump will run that backup heater for hours at a time. A 10 kW backup heater (common in 3-ton systems) draws about 42 amps on a 240-volt circuit by itself. That's why your total amperage during winter heating can be so much higher than during summer cooling — you're not just running the compressor, you're running the compressor plus a space heater.

How to read your heat pump's nameplate for actual amperage

The most reliable number is on the equipment itself. Look for a metal or plastic label on the outdoor unit (the condenser) and the indoor unit (the air handler). The outdoor unit will list RLA (Running Load Amperage) or FLA (Full Load Amperage) for the compressor. The indoor unit will list the amperage for the backup heater separately, usually labeled as "Electric Resistance Heat" or "Supplemental Heat".

RLA is the number you want — it's the actual amperage the compressor draws during steady operation, not a theoretical maximum. FLA is sometimes higher and represents a worst-case scenario. If your nameplate shows RLA of 18 amps for the compressor and 42 amps for a 10 kW heater, you now know that running both at once will draw 60 amps total, which is why your electrician installed a 60-amp subpanel or a 50-amp breaker with a tandem configuration.

If you can't find the nameplate or it's faded, the model number is usually printed there too. You can search the manufacturer's website or call their technical support line with the model number, and they'll send you the spec sheet with exact amperage ratings.

What happens if your breaker keeps tripping

A breaker that trips once in a blue moon during a cold snap is normal — it means the system is working as designed and the breaker is protecting the circuit. A breaker that trips repeatedly is a sign something is wrong, and the problem is almost never the compressor itself.

The most common cause is the backup heater running too often. If your heat pump is set to a very low balance point (say, 20 degrees) but your area regularly hits 30 degrees, the heater will run constantly and draw more power than the circuit can handle. The fix is to raise the balance point in your thermostat settings so the backup heater only kicks in when truly necessary. Your HVAC technician can adjust this — it's a straightforward setting change, not a hardware replacement.

The second common cause is a failing compressor that draws more amperage than it should. If the breaker trips even when the backup heater is off, or if it trips during mild weather when the heater shouldn't be running at all, call your HVAC technician. A compressor drawing excessive amperage is a sign of internal wear or a refrigerant problem, and it won't fix itself.

A third possibility is that the circuit itself is undersized — the original installation was done with a 30-amp breaker when it should have been 40 or 50 amps. This is rare in modern installations but can happen in older homes where a heat pump was retrofitted into an existing electrical setup. If you suspect this, have a licensed electrician inspect the installation.

Sizing your electrical panel for a 3-ton heat pump

Your electrician will use a formula based on the compressor RLA and the heater amperage to determine the correct breaker size. The National Electrical Code (NEC) requires the breaker to be sized at 125 percent of the compressor's RLA, plus 100 percent of the heater amperage. For a typical 3-ton unit with an 18-amp compressor and a 42-amp heater, that's (18 × 1.25) + 42 = 64.5 amps, which rounds up to a 70-amp breaker or subpanel.

In practice, most 3-ton heat pumps are installed on a 40 to 60-amp dedicated circuit. The exact size depends on your specific model and your local electrical code. If you're planning to install a heat pump and want to know what your panel needs to support, get a quote from a licensed electrician — they'll pull the equipment specs and calculate the right size for your situation.

Cooling versus heating amperage

During summer cooling, your heat pump draws less total amperage than during winter heating, because the backup heater is off. The compressor alone will draw 15 to 20 amps, and that's it. This is why some homeowners are surprised by their winter electric bills — the same unit that ran quietly all summer suddenly seems to be drawing a lot more power when the weather turns cold.

The heat pump is not broken; it's just working harder and using a less efficient heating method (the backup heater) to meet demand. If you want to reduce winter amperage draw, the real solution is to improve your home's insulation and air sealing so the heat pump doesn't have to work as hard. Running the backup heater less often is the only way to meaningfully lower winter electricity use.

Frequently Asked Questions

Will a 3-ton heat pump overload a 100-amp home electrical panel?

No. A 100-amp panel is standard for most homes and is sized to handle a heat pump plus all other household loads. The heat pump itself will use 40 to 60 amps of that total capacity, leaving plenty for lights, appliances, and other circuits. If your panel is older and already near capacity, an electrician can install a subpanel dedicated to the heat pump.

Does a heat pump use more electricity than a furnace?

In moderate climates, a heat pump uses less electricity than electric resistance heating because it moves heat rather than creating it. In very cold climates where the backup heater runs constantly, a heat pump can use more electricity than a gas furnace, but it's still more efficient than a pure electric furnace. The comparison depends on your local climate and energy prices.

Can I run my heat pump on a 30-amp breaker?

Not safely. A 30-amp breaker is too small for a 3-ton heat pump. The compressor alone draws 15 to 20 amps, and adding the startup surge and any backup heater operation will trip the breaker. A 40 to 50-amp breaker is the minimum for a 3-ton unit.

What's the difference between RLA and FLA on the nameplate?

RLA (Running Load Amperage) is what the compressor actually draws during normal operation. FLA (Full Load Amperage) is a theoretical maximum that accounts for worst-case conditions like high outdoor temperature or low refrigerant charge. Use RLA for sizing your breaker and estimating electricity draw.

Why does my heat pump draw more amps in winter than summer?

In winter, the backup electric heater runs to supplement the compressor when outdoor temperature is cold. The heater alone can draw 40+ amps, so total system amperage is much higher than in summer when only the compressor runs. This is normal and expected.