Whenever you have a power outage, every heat pump owner wants to know one thing:

*“How much electricity does a heat pump use?”*

Knowing how many watts does a heat pump use is useful in a number of cases, including:

*How much does it cost to run a heat pump?*(They are considered very energy-efficient)*How big a generator do you need to run a heat pump?*(Start-up wattage is key here)*Will a solar panel system be able to provide enough electricity to power a heat pump?*

How much electricity does a heat pump use?

Heat pumps use anywhere from **802 watts to 5,102 watts ***(that is between 0,802 kWh to 5.102 kWh per hour)*, costing anywhere from **$0.10 to $0.98 per hour** to run. Starting wattage (relevant for generator size) can be 3 times higher still; between *2,406 W and 15,306 W*.

This is quite a large spectrum. In order to figure out your much electricity does your heat pump use, you have to consider 3 main factors that the heat pump wattage depends on:

**Size or capacity (tonnage);***primary factor.*The bigger the heat pump, the more power it will need to run.*Example:*4-ton heat pump will use more electricity than a 2-ton unit.**Energy efficiency (SEER rating);***primary factor.*The more efficient the heat pump, the fewer watts it will require to run.*Example:*14 SEER 3 ton heat pumps draws 3,061 watts. 22 SEER 3 ton heat pump draws 2,406 watts; that’s quite a big difference.**Type of heat pump;***secondary factor.*In general, same size ground-source heat pump requires less electricity to run than an air-source heat pump (due to higher SEER rating).

Now, determining exactly how many watts does a heat pump require to run isn’t all that easy. If you crack open the specification sheet of a heat pump, you will rarely see something like “Max. Wattage = 3,000W”.

What you will always find in the specs sheet, however, is the SEER rating. We can use SEER rating to determine how many watts and amps do you need to run such a heat pump. First of all, we will look at how to get to the wattage of any heat pump via SEER rating.

Further on, you will also find how many watts do 1-5 ton heat pumps use (summarized in a table).

### How To Check How Many Watts Does A Heat Pumps Use?

As you know, wattage is not labeled on the heat pump spec sheet. Fortunately, SEER rating (Seasonal Energy Efficiency Rating) is. We can calculate the total wattage heat pump uses from SEER rating using these two equations:

EER = −0.02 × SEER² + 1.12 × SEER (Equation 1)

Total Wattage = Capacity (In BTUs) ÷ EER (Equation 2)

In short, we convert SEER to EER (Equation 1), and we use the calculated EER to calculate the total wattage of a heat pump (Equation 2). It might sound a bit complex but it’s quite easy; you just insert the SEER rating in Equation 1 and go from there.

Here’s an example of what we get:

A 2-ton heat pump (24,000 BTU) has a 20 SEER rating. How many watts does it run on? Let’s calculate that:

EER at 20 SEER = −0.02 × 20² + 1.12 × 20 = 14.4

Total Wattage (2-ton, 20 SEER) = 24,000 BTU ÷ 14.4 = **1,667 Watts**

Using these two equations, we can calculate how much power does any heat pump use. We did just that and summarized the results in this table:

## How Many Watts Do Heat Pumps Use?

Heat Pump Size: |
Wattage (14 SEER): |
Wattage (16 SEER): |
Wattage (18 SEER): |
Wattage (20 SEER): |
Wattage (22 SEER): |

1 ton (12,000 BTU) |
1,020 W | 938 W | 877 W | 833 W | 802 W |

1.5 ton (18,000 BTU) |
1,531 W | 1,406 W | 1,316 W | 1,250 W | 1,203 W |

2 ton (24,000 BTU) |
2,041 W | 1,875 W | 1,754 W | 1,667 W | 1,604 W |

2.5 ton (30,000 BTU) |
2,551 W | 2,344 W | 2,193 W | 2,083 W | 2,005 W |

3 ton (36,000 BTU) |
3,061 W | 2,813 W | 2,632 W | 2,500 W | 2,406 W |

3.5 ton (42,000 BTU) |
3,571 W | 3,281 W | 3,070 W | 2,917 W | 2,807 W |

4 ton (48,000 BTU) |
4,082 W | 3,750 W | 3,509 W | 3,333 W | 3,209 W |

4.5 ton (54,000 BTU) |
4,592 W | 4,219 W | 3,947 W | 3,750 W | 3,610 W |

5 ton (60,000 BTU) |
5,102 W | 4,688 W | 4,386 W | 4,167 W | 4,011 W |

Using this table, you can answer pretty much any question regarding how many watts does your heat pump run on.

*Example:* Let’s say you have a 16 SEER 3 ton unit. How many watts does it require to run? Just check the table and you will see that such a 3-ton unit runs on 2,813 W.

This is quite valuable information if you’re looking at what wattage generator you need to run a 3-ton unit.

We hope this helps. If you haven’t found the answer in the article above, you can give it as a comment below and we’ll try to help you out with the calculation.

Table of Contents

Thanks for your help.

I’m getting solar panels that will cover some 120% of my current consumption 16K kw/h year. This means 19000 kw/h. I’m looking into a 4 ton 17 seer heat pump around 10 hspf as a way of switching from my current oil heat system. I’m having a hard time figuring out how much extra electricity this heat pump will consume and if it would be mostly covered by the solar panel production. I live in Connecticut so I expect around 2300 hours of heating need per year. Can you help? Thanks so much.

Hello Joseph, good idea about solar panels. A 4 ton 17 SEER HVAC unit running at 100% output should have a running wattage of about 3,600W. Running such a unit for 8 hours per day at 100% output will burn through 28.8 kWh. Now, in most cases, you are running it much below 100%. Given how the SEER rating is calculated, it’s presumed that you run it, on average, at 58% output. That reduces running it for 8 hours to 16.13 kWh per day. Similar numbers are for heating (10 HSPF rating).

If you run it for 2300 hours per year, that would be 6.3 hours per average day, yielding 12.7 kWh per day. But you will probably use it in the winter much more than in the summer months. This is a way how you can theoretically try to evaluate is the solar panels will be sufficient. Hope it helps a bit in understanding how to do these calculations.

Hello LM- I have 5T Geothermal heat pump with a scroll compressor.

The compressor mfr. says it has a 10.4 EER (approx. 12 SEER).

Compressor RLA 26.0, LRA 118.0, Total FLA 32.8. Min amps 39.3, Max Fuse

Breaker 65. My question: How many starting watts of power or amps do I need? I’m trying to figure out what size(KW) whole house generator are needed. Thank-you

Hello Mel, you can consult our article about what size whole house generator you need here. Basically, heat pumps can have quite high starting watts; about 2x or 3x of running wattage. A 5-ton unit should have about 5,000W running wattage. That means you need anywhere from 10,000W to 15,000W start wattage.

The starting wattage should be labeled on the unit itself. Alternatively, you can also check the specs sheet. Hope this helps a bit.

Just a note on start up surge. I have monitored my new dual inverter heatpumps and there is no more surge. The inverters ramp up slowly over approximately 1 to 2 minutes when starting. This would make it much easier to start with a generator.

Hi Paul, yes, no surge is a literal blessing. You need a lot smaller generator to run a heat pump if the heat pump doesn’t have a start up wattage much higher than the running wattage.

How did you derive the 58% on average. Thanks—

Hello Henry, that’s quite an interesting question. Namely, we use a formula for SEER rating to derive that number. SEER rating tries to capture the real-life outputs of AC units. It presumes that the unit will run 1% of the time at 100% output, 42% of the time at 75% output, 45% at 50% output, and 12% at 25% output. If you calculate the weighted average of the average output, you get that a unit will run at the equivalent of 58% output. Hope this makes sense.

Got it. Thanks. This is very helpful in calculating hourly energy and then cost.

I am having a tough time considering a heat pump more efficient and less costly to use. My Daikin 16 seer says an avg of 4.75 kw a day and yet I am finding pellet stoves of 1 kw or less per day for my 1200 sq foot home.

Hi Richarda, well, to adequately compare the two, you have to put all the numbers on a sheet of paper and calculate from that. In many cases, heat pumps are a better solution since they cost less to run and offer air conditioning in the summer as well.

I am trying to determine if my electrical feed can handle a heat pump. I have calculated the wattage of the heat pump by using your formula from the SEER rating and have determined that the heat pump will run at 2,907 watts. Do I have to add anything to this to account for startup wattage when calculating the total load for my supply feed or do I just use the running wattage as the amount. I have calculated my spare capacity wattage as 4,600 watts. Do I simply subtract 2,907 from 4,600 (~1,700 remaining spare capacity) to confirm that I have the capacity to install the heat pump without worry of overloading the circuit? Or do I have to calculate the startup wattage (3 times as per you article above or ~8,700 watts) and subtract this amount?

Hi Bernie, thanks for all these numbers. Now, SEER is calculated with the presumption that the heat pump runs at 58% of the max. wattage. The start-up wattage is always hard to find; the 3 times the running wattage is the rule of thumb for air conditioning. You do have to add quite a lot on top on 2,907 watts for start up wattage.

Namely, with 4600W capacity, you will definitely be able to run the heat pump. However, starting is the key question (AC and heat pumps are notoriously hungry as far as start up watts are concerned). I’m afraid you will need close to 8,700 watts for starting the unit. Hope this clears things a bit.