Cost to Run a Mini Split: Monthly Electricity Estimates
What a mini split costs to run per hour and per month by size, how to estimate your own bill from BTU, EER2 and your electric rate, and why inverters bill less.
A 12,000 BTU mini split draws roughly 1 kilowatt at full cooling, which is about 17 cents an hour at the U.S. average residential rate of about 17 cents per kilowatt-hour. At 8 hours a day that is near $40 a month. Because inverter compressors spend most of their time at part load, your real bill is usually lower. Here is how to estimate it for your own unit and rate.
How much does it cost to run a mini split per month?
A single head costs a few tens of dollars a month in typical use. The table below assumes the U.S. average residential electricity price of about 17 cents per kilowatt-hour (EIA, 2025) and 8 hours of daily cooling at full compressor draw, which is a conservative high estimate.
| Head size | Full-draw power | Cost per hour | ~8 hrs/day, 30 days |
|---|---|---|---|
| 9,000 BTU | ~0.75 kW | ~$0.13 | ~$31 |
| 12,000 BTU | ~1.0 kW | ~$0.17 | ~$41 |
| 18,000 BTU | ~1.5 kW | ~$0.26 | ~$61 |
| 24,000 BTU | ~2.0 kW | ~$0.34 | ~$82 |
These are ceilings, not averages. An inverter compressor ramps down once the room reaches setpoint, so the head often runs at a third to half of full power. Expect real bills below the table in mild weather and closer to it in a heat wave.
How do I calculate my own running cost?
Three numbers give you the answer: the BTU rating, the efficiency rating, and your electric rate. The formula is watts equals BTU divided by EER2.
- Find the cooling capacity (for example 12,000 BTU) and the EER2 on the spec sheet (often 11 to 13 for a modern mini split).
- Divide: 12,000 / 12 equals 1,000 watts, or 1 kilowatt.
- Multiply by your rate: 1 kW times $0.17 equals $0.17 per hour at full draw.
- Multiply by daily hours and days for a monthly figure.
Your rate is the lever that matters most. At 12 cents the 12k head costs about $0.12 an hour; at 30 cents it costs about $0.30. Check your utility bill for your actual cents-per-kilowatt-hour before trusting any published estimate.
Why do mini splits cost less to run than central air?
Two reasons: no duct losses and a modulating compressor. ENERGY STAR estimates that 20 to 30% of the air moving through a typical duct system is lost to leaks and poor connections. A ductless head delivers all of its conditioned air into the room.
The inverter compressor is the second reason. A conventional AC runs at 100% or 0% and cycles on and off. An inverter mini split varies its speed, settling at a low, steady output that matches the room’s load. That part-load running is where the efficiency gap shows up on the bill. Our energy-efficient mini split guide explains SEER2 and HSPF2 and which DIY models rate highest.
What does it cost to heat with a mini split?
Heating is cheap in mild weather and more expensive in deep cold. A heat pump moves heat rather than making it, so its coefficient of performance (COP) is often 3 or more in mild conditions, meaning 1 kilowatt of electricity delivers about 3 kilowatts of heat.
As the outdoor temperature drops, capacity and COP fall. ENERGY STAR lists MRCOOL’s DIY 5th Gen 12k at 8,400 BTU per hour at 5 F, about 70% of its rating, so the unit runs longer and draws more to hold the room. A rough cold-day estimate: a 12k head delivering heat at a COP near 2 uses about 1.5 to 2 kilowatts while running. In a cold snap it may lean on a backup heat source, which changes the math.
How does running cost compare to other systems?
A mini split usually beats electric resistance heat and window units on operating cost. ENERGY STAR states that certified ductless systems can use up to 60% less energy than standard electric resistance heating and up to 30% less than standard window air conditioners.
| System | Relative running cost | Why |
|---|---|---|
| Mini split (inverter) | Low | No duct loss, part-load modulation, high SEER2/HSPF2 |
| Central AC with ducts | Medium | 20-30% duct losses, on-off cycling |
| Window AC | Medium to high | Lower efficiency, no modulation |
| Electric baseboard heat | High | COP of 1; no heat-pump multiplier |
Upfront cost runs the other way: a mini split often costs more to buy and install than a window unit. See the installation cost guide for purchase and install pricing, and the pros and cons page for the full trade-off.
How can I lower my mini split running cost?
Size and settings do most of the work. A right-sized head that runs long and slow is cheaper and more comfortable than an oversized one that short-cycles, so start with our sizing calculator.
- Hold a steady setpoint. Inverter units are efficient at part load; deep swings make the compressor restart at full power.
- Clean the filter every two weeks in season. A clogged filter cuts airflow and raises run time (MRCOOL DIY manual).
- Keep the outdoor unit clear. Blocked airflow lowers efficiency.
- Use eco or low fan modes for background comfort rather than turbo.
- Zone off empty rooms on a multi-zone system.
For the best efficiency per model, the best DIY mini split guide lists the highest SEER2 units.
Where do these numbers come from?
- U.S. Energy Information Administration (EIA) residential electricity price, about 17 cents per kilowatt-hour average in 2025.
- ENERGY STAR ductless heating and cooling and duct sealing pages, read October 2026: the 60% versus electric resistance figure, the up-to-30% versus window AC figure, and 20 to 30% duct losses.
- ENERGY STAR Certified Mini-Split Heat Pumps dataset and MRCOOL DIY 5th Gen catalog (V 09.16.26): capacity at 5 F, EER2 and SEER2 ratings.
- Watts-from-BTU method: watts equals BTU divided by EER2, a standard HVAC calculation.
Frequently asked questions
Quick answers to what readers ask us most
How much does it cost to run a mini split per month?
For a 12,000 BTU head at 8 hours a day, roughly $35 to $45 a month at the U.S. average rate. A 9k runs less, an 18k or 24k runs more. Heating in cold weather costs more per hour than cooling because capacity drops and run time rises.
Do mini splits use a lot of electricity?
Less than most alternatives. A ductless head avoids the 20 to 30% duct losses ENERGY STAR cites for central systems, and inverter compressors throttle down instead of cycling on and off. A single 12k head at full draw is about 1 kilowatt, similar to a hair dryer on low.
How do I calculate my own mini split running cost?
Divide the BTU rating by the EER2 to get watts, divide by 1,000 for kilowatts, then multiply by your electric rate and your daily hours. A 12,000 BTU unit at EER2 12 is 1,000 watts, so 1 kWh per hour times your rate.
Is it cheaper to leave a mini split on all day or turn it off?
For an inverter mini split, holding a steady setpoint is usually efficient because the compressor idles at low power rather than restarting at full power. Big setbacks still save energy over long absences, but short on-off cycling gains little and can feel less comfortable.
Does a mini split cost more to heat or to cool?
Heating usually costs more per season in a cold climate because capacity falls as the temperature drops, so the unit runs longer and may lean on backup heat. In mild heating weather a heat pump is very cheap to run thanks to its high coefficient of performance.