We usually choose an air conditioner based on BTU and room size. However, when we’re trying to estimate energy costs, it’s very useful to know how many watts our particular air conditioner use.
How many watts does an air conditioner use?
Air conditioner wattage is not the easiest information to come by.
Not knowing how many watts does a 5,000 BTU air conditioner use is actually pretty normal. As far as lowering the air temperature is concerned, you only need to know that it has 5,000 BTU and is correctly sized for your room/space. Most homeowners don’t actually know their air conditioner wattage.
An average 5,000 BTU air conditioner uses 500W of energy running at full capacity. Below we also specify an estimate of how many watts does a window, portable, and mini-split AC use. We are talking about air conditioner power rating in watts.
You can estimate how many watts does an air conditioner with known capacity (BTU) use pretty well with this AC wattage calculator:
There are 3 ways how to check how many watts does your air conditioner use:
- Check the specification sheet for Watts. You’ll find the power or wattage (in Watts) in the same section as amperage (in Ampers) and voltage (in Volts).
- Check the specification sheet for Ampers and Volts. The power is simply calculated by multiplying the number of Ampers with the number of Volts (something like 10A * 120V = 1,200W).
- Use BTU and EER rating to calculate how much power does your air conditioner use. You can divide the BTU by EER rating (something like 5,000 BTU / 10 EER = 500W).
Below you find a table of how many watts do different air conditioners – from 5,000 BTU to 18,000 BTU – use.
A rule of thumb to estimate how many watts of energy different air conditioners use is to take the BTU number and divide it by 10. That’s how you can easily estimate that 5,000 BTU AC units use 500W of energy.
How Much Power Do Air Conditioners Use?
The relationship between BTU and the power (in watts) of an air conditioner is determined by the energy-efficiency EER rating. A good EER rating, for example, is 10. That means that 500W will give us 5,000 BTU of cooling effect. If an air conditioner had a higher EER rating (12, for example), the 500W would give us 6,000 BTU of cooling effect.
In the table above, we’ll assume that the EER rating of all AC units is between 8 and 12. That’s why you’ll see a range for the wattage of air conditioners with the same BTU number:
| BTU: | Wattage: |
|---|---|
| How many watts does a 5000 BTU AC use? | 417 – 625 W |
| How many watts does a 6000 BTU AC use? (1/2 ton) | 500 – 750 W |
| How many watts does an 8000 BTU AC use? | 667 – 1000 W |
| How many watts does a 10000 BTU AC use? | 833 – 1250 W |
| How many watts does a 12000 BTU AC use? (1 ton AC wattage) | 1000 – 1500 W |
| How many watts does a 15000 BTU AC use? | 1250 – 1875 W |
| How many watts does an 18000 BTU AC use? (1.5 ton AC wattage) | 1500 – 2250 W |
Example 1: What is 1 ton AC wattage? A 1-ton air conditioner (12,000 BTU) with a 10 EER rating has a 1,200 wattage.
Example 2: What is 1.5 ton AC wattage? A 1-ton air conditioner (18,000 BTU) with a 10 EER rating has a 1,800 wattage.
You can pretty much figure out what is any AC wattage using EER. Here is the AC wattage formula based on EER rating:
AC Wattage = AC Capacity (in BTU) / EER Rating
Let’s say you want to figure out the AC wattage of a 2-ton unit with a 12 EER rating. Here is the wattage calculation:
2 ton AC Wattage = 24,000 BTU / 12 = 2,000 W
That means that a 2-ton AC has a 2,000W wattage.
As you can see from the table above, a 12,000 BTU air conditioner can use 1500W (8 EER rating) or 1000W (12 EER rating). In short, having a high energy efficiency air conditioner with a high EER rating pays off. We have gathered the most energy-efficient portable AC units here.
How Many Watts Does A Window AC Use? (500 – 2,500W)
Window air conditioners can generate anywhere from 5,000 BTU (check the smallest window AC units here) to 25,000 BTU (check the biggest window AC units here) of cooling output.
In general, the EER rating of window AC units ranges from 8 EER (energy inefficient) to 12 EER (energy efficient).
Based on these two factors – cooling output (BTUs) and energy rating (EER) – we can calculate how many watts does a window AC use. For that, we use this EER equation:
EER Rating = BTU Output / Max. Wattage
Let’s express ‘Max. Wattage’ in this way:
Max. Wattage = BTU Output / EER Rating
If we presume that an average EER rating of a window AC unit is 10, we can easily calculate window AC wattage with a certain BTU cooling output. Window AC wattage ranges from 500 watts to 2,500 watts.
For example, a 14,000 BTU window air conditioner with a 10 EER rating draws:
Max. Wattage = 14,000 BTU / 10 EER = 1,400 Watts
Such a window air conditioner uses 1,400 watts. Based on 10 EER rating, we have calculated the wattages of both small and big window air conditioners with 5,000 BTU to 25,000 BTU cooling outputs:
| Window AC Unit Capacity (in BTU): | Power Draw (in Watts): |
| 5,000 BTU | 500 watts |
| 6,000 BTU | 600 watts |
| 7,000 BTU | 700 watts |
| 8,000 BTU | 800 watts |
| 9,000 BTU | 900 watts |
| 10,000 BTU | 1,000 watts |
| 11,000 BTU | 1,100 watts |
| 12,000 BTU | 1,200 watts |
| 13,000 BTU | 1,300 watts |
| 14,000 BTU | 1,400 watts |
| 15,000 BTU | 1,500 watts |
| 16,000 BTU | 1,600 watts |
| 17,000 BTU | 1,700 watts |
| 18,000 BTU | 1,800 watts |
| 19,000 BTU | 1,900 watts |
| 20,000 BTU | 2,000 watts |
| 21,000 BTU | 2,100 watts |
| 22,000 BTU | 2,200 watts |
| 23,000 BTU | 2,300 watts |
| 24,000 BTU | 2,400 watts |
| 25,000 BTU | 2,500 watts |
These are rough estimates of how many watts do window air conditioners use.
We can use the same principle to calculate how many watts do portable and mini-split air conditioners use:
How Many Watts Does A Portable AC Use? (940 – 1,650W)
Portable air conditioners use, on average, more watts than window AC units. That is because the average EER rating of a portable AC unit is 8.5; portable units will need, on average, about 15% more watts for the same output. This means that portable AC wattage ranges between 940 watts and 1,650 watts.
The cooling output of the portable air conditioners ranges from 8,000 BTU to 14,000 BTU.
Here is a table of how many watts do portable air conditioners use:
| Portable AC Unit Capacity (in BTU): | Power Draw (in Watts): |
| 8,000 BTU | 940 watts |
| 9,000 BTU | 1,060 watts |
| 10,000 BTU | 1,180 watts |
| 11,000 BTU | 1,300 watts |
| 12,000 BTU | 1,410 watts |
| 13,000 BTU | 1,530 watts |
| 14,000 BTU | 1,650 watts |
These are estimates of how many watts do portable air conditioners draw.
How Many Watts Do Mini Split Air Conditioners Use? (500 – 2,500W)
Mini-split air conditioners are more energy-efficient than the window and portable AC units and thus draw fewer watts and amps for the same cooling output. On average, the EER rating of mini-split AC units is about 12.
Mini-split AC units can be very small (9,000 BTU), mid-range (24,000 BTU), and we also have the big multi-zone units with up to 60,000 BTU (5-tons) of cooling output.
To answer how many watts does your mini split AC unit use, you can consult this table (with presumed 12 EER rating for all units):
| Mini-Split AC Unit Capacity (in BTU): | Power Draw (in Watts): |
| 9,000 BTU (0.75 tons) | 750 watts |
| 12,000 BTU (1 ton) | 1,000 watts |
| 18,000 BTU (1.5 tons) | 1,500 watts |
| 24,000 BTU (2 tons) | 2,000 watts |
| 30,000 BTU (2.5 tons) | 2,500 watts |
| 36,000 BTU (3 tons) | 3,000 watts |
| 42,000 BTU (3.5 tons) | 3,500 watts |
| 48,000 BTU (4 tons) | 4,000 watts |
| 54,000 BTU (4.5 tons) | 4,500 watts |
| 60,000 BTU (5 tons) | 5,000 watts |
Note about RV air conditioners and wattage: How many watts do RV air conditioners draw? An average 15,000 BTU RV air conditioner will require about 1,500 watts to run. However, it will need about 3,000 watts or even 3,500 watts start-up wattage.
When you figure out how many watts does an air conditioner draws, you can calculate how much it costs to run such an AC. That is, if you have a continuous source of electricity, which brings us to the next chapter:
Best Generators For Air Conditioners
If you don’t have a source of electricity readily available, you’ll most probably need a generator to create about:
- 500 W for 5,000 BTU AC unit. Here is a calculation of what size generator you need for a 5000 BTU air conditioner.
- 1,000 W for 10,000 BTU AC unit.
- 1,500 W for 15,000 BTU AC unit.
For bigger air conditioners (1-6 ton), you can check the calculation of what size generator do you need for a 5-ton air conditioner here.
We’ve received many questions about which generators are best for a certain capacity of an air conditioner. Here are some of the generators you can use:
- Jackery Portable Power Station Explorer 500W for small 5,000 BTU units.
- Jackery Portable Power Station Explorer 1000W for medium 10,000 BTU units.
- Honda EU2200i 2200W for larger 15,000 BTU to 20,000 BTU units.
All these generations will cover the basic wattage needed to power your air conditioner.
Cost Of Running A 1,000 W Air Conditioner (Estimate)
High wattage air conditioners cost more to run. For example, a 1000W AC unit spends 1 kilowatt-hour of electricity per hour. 1500W unit, for comparison, spends 1.5 kWh of electricity per hour.
Given that an average price of 1 kWh in the US is $0.1319, you can save quite a bit if you invest in an above-average energy-efficient air conditioner.
The average cost of running a 1000W air conditioner is thus $0.1319 per hour. That translates to about $1 for air conditioning if you run such a unit for 8 hours a day.
What btu rating if any can be run by a 1000watt LP generator? Thank you.
Hello Andy, 1,000W can power a 8,000 to 12,000 BTU device; depending on the EER rating.
What size of generator to run a 1.5 hp deep well pump ? Thanks
Hello Celso, what is the wattage of that pump?
Im worried about start up watts needed to run my 10000 BTU space cooler and refrigerator start up. How big of a generator do I need?
Hello Deidre, you would need a generator that can produce up to 1,500W. Green-Power America GPD1500 1500W would be an excellent choice for that.
The example for the 12000 BTU ac is backwards, the 8 EER will consume 1500w and the 12 EER will consume 1000w
Hello Mogman, you’re exactly right, thank you for the heads-up; we’ve fixed the numbers according to your suggestion.
I have a 1 1/2 HP Submersible pump, Unfortunately, they take surge watts of 7,500 & RUNNING is 2,500 watts. I wish my water well installer would have told me this before he installed. (My aerated compressor system used under 5,000). I just purchased a 8000 watt gas generator as nothing I had could carry the huge load. (Here’s the generic list from EMP (NASA) specialist = Water Well Pumps RATED RUNNING 1,000-2,500, Surge/STARTING 5,600 – 7,500 watts & required voltage 120 or 240
Hello Deborah, you’re right, with Submersible pumps, you will have a significantly higher start-up wattage. While a 3000 W generator could run the pump, it can’t be used to start it up. The initial surge can be up to 3x or 4x higher than running wattage.
Hi, i would like to ask if the 3000watts step up & down transformer compatible to insignia portable aircon the capacity is 10,000 BTU ,60Hz, 15A, and 1560W.? Thank u in advance
Thank you so much for this wattage calculator! I don’t think companies get that some (maybe most) customer may want to know the total wattage output before they purchase an item. It’s so true that information about how many watts an item uses is very hard to find.
Thanks, again!
I have a 9000 btu, 980 watt portable ac with 115 volts and 9.2 amps. Will a 2300watt generator be enough for the surge to start it?
Hello Jim, the start wattage should be 2-3 times the max. running wattage. 2300W generator might just cut it. It’s really hard to know for sure, however.
My question is, how big of an generator would I need to run a 13,500 BTU, roof top AC for my RV?
I currently have a 8,000 BTU stand up AC, with a 1800/2300 generator, and it’s not allowing the compressor to kick on. I was thinking maybe it’s the cable size or length? Thank you for your help!
Hello Holly, it depends on the wattage. 13,500 BTU units usually require 1,500W to run; and about 3,000W or 4,000W for the startup. A 5,000W generator should be sufficient; you can run all kinds of other devices that require electricity on that generator.
I’m looking here for BTU to Wattage conversion and I see what I think is an error on the page.
In the following section, shouldn’t the Wattage be 2,000 rather than 20,000?
“You can pretty much figure out what is any AC wattage using EER. Here is the AC wattage formula based on EER rating:
AC Wattage = AC Capacity (in BTU) / EER Rating
Let’s say you want to figure out the AC wattage of a 2-ton unit with a 12 EER rating. Here is the wattage calculation:
2 ton AC Wattage = 24,000 BTU / 12 = 20,000 W
That means that a 2-ton AC has a 20,000W wattage.”
Hello there, oh yes, thank you! 2 ton AC and 20,000 watts is wrong. Shame on us. We have corrected it to 2,000 watts, thanks again for the heads up.
Hello
Question, I have a inverter of 3000 Watts, do you think it can run 2 x AC portable units
2x Portable AC Unit Capacity (in BTU): Power Draw (in Watts):
8,000 BTU – 940 watts
Hello Lewis, running them shouldn’t be a problem; you can 3000 Watts inverter and 2 portable AC units draw max. running wattage of 1880 Watts. No problem here. You might have a problem with a start-up wattage; it can be 2-3x higher than running wattage. Don’t turn them on at the same time.
I have a 7000 but portable ac and I just recently bought an 1800w generator is this enough for the ac or what do I need
Hello Amanda, the running wattage of a 7,000 BTU portable AC is usually about 700W. The start-up wattage can be quite high, above 1500W+. If the generator will start the AC, you have more than enough wattage to run it even at 100% cooling output.
Hi there and thank you for such a helpful breakdown of such a complicated subject
My question is this, there is this split system
the Gree 9,000 BTU 38 SEER SAPPHIRE
since the sEEER rating is 38 is this then actually using only 236.842 watts per hour at high speed, and since most are only coming on 2 to 3x in a hour since they are just keeping the temp, say at 74 degrees, does that also mean in actual usage its using half of that 236.842 watts? Say 118 watts? If it only comes on for 30 min in a hour.
And if the mini splits temp is set even higher say 77 degrees does this get even more energy efficient? I guess this question is more about the ratting, is it for the highest setting and for a full hour of use, so real world what should one expect from such a unit. The reason and the holy grail is to run a mini split in a small RV with just solar, I understand this unit I am asking about is well over 1k to buy but if it allows for total comfort its priceless.
Hi John, these new mini splits like the Gree Sapphire line have an astonishingly high SEER rating. You got the correct watts per hour there (236.842W). This is based on the SEER rating; SEER rating is a weighted-average efficiency that presumes that the unit runs at 58% output. So, at full power (100% output), you are going to see about 408W power draw (also be careful about start-up wattage for use in RVs).
Here a rule of thumb of how much electricity this unit would burn per day: Let’s presume you run it for 8 hours at an average 58% output. That’s a total of 1895 Wh or 1.895 kWh per day. Now, if you have 500W solar panels and get 5 peak sun hours per day, that’s 2.5 kWh. That should be enough to run this mini split continuously with just the solar panels.
Mini splits are pretty much the quietest type of air conditioners. You can’t really get more quiet than that. Most of them will have the indoor unit noise levels below 50 dB, some even below 40 db. Hope some of this helps you make the right decision.
What size of generator to run a goodman 2.5 Ton 13 seer? Thanks
Hi Alexone, alright, 2.5 tons is 30,000 BTU; at 13 SEER (58% output), it will run on 2308 watts. That means that the max. wattage is about 3979 watts. So, a 3979-watt generator is a minimum. The question is what is the start-up wattage of this unit. You will likely need a 5000+ watt generator. You can check out our article about generator sizing here; it will give you a valuable insight into start-up wattage. In short, 10kW generator would be a safe choice here.
Hello, you mention the jackery 1000 for a 10000 btu unit. If i am understanding correctly that will only run the unit for 1 hour, is that correct?
Hi Colt, yes, it has a 1,002 Wh capacity, that’s basically 1000W for 1 hour.