Mini Split Running Cost Calculator
Enter the head's BTU, its SEER2 (cooling) or HSPF2 (heating) and the hours it runs, and get the cost per hour, day and month in your state, with inverter modulation included.
Mini split cost
A05Scenario A
Sets the electricity rate. Pick US average if you're not sure.
From EIA for US average. Use the rate on your bill if you know it.
Rate used: 18.4¢/kWh · US average · EIA reference 2025–26 (data as of 2026-09-26) ·
Inverter units rarely run at full power. 0.6 means an average of 60% of maximum.
Estimated cost per month
- Maximum watts600 W
- Average watts (modulation 60%)360 W
Per year assumes the same use every day.
Estimate. Formula and sources are under “How it works”. Change any input; the result updates as you type.
Formula
How it works
- Cooling, maximum watts = BTU ÷ SEER2
- Heating, maximum watts = (BTU ÷ 3,412) × 1,000 ÷ COP, where COP = HSPF2 ÷ 3.412
- Average watts = maximum watts × modulation factor
- kWh per day = average watts ÷ 1,000 × hours
- Cost per month = kWh per day × days × rate
An inverter mini split speeds its compressor up and down instead of switching it on and off, so average draw is typically 40–70% of maximum. A 12,000 BTU head at SEER2 20 draws up to 600 W cooling. In heating mode it draws more for the same BTU; in the NY example below, 1,412 W at maximum.
Sources: SEER2 and HSPF2 definitions (AHRI 210/240-2023); COP ≈ HSPF2 ÷ 3.412. Electricity rate: EIA Electric Power Monthly table 5.6.A. Note: heat pumps lose capacity in deep cold (below about 25 °F). This calculator doesn't model that loss, so treat winter heating results in cold states as a low estimate.
Worked example
A worked example
An 18,000 BTU head at SEER2 22 draws at most 18,000 ÷ 22 = 818 W. At a modulation factor of 0.6 it averages 491 W, or 4.91 kWh over 10 hours. At the Texas rate of 15.5¢/kWh that's $0.76 a day and $23.59 for a 31-day month.
Reference
Reference table
Mini split cooling cost per month at 18.4¢/kWh (US average), modulation 0.6, 8 h a day
| SEER2 16 | SEER2 20 | SEER2 24 | |
|---|---|---|---|
| 9,000 BTU | $14.90 | $11.92 | $9.94 |
| 12,000 BTU | $19.87 | $15.90 | $13.25 |
| 18,000 BTU | $29.81 | $23.85 | $19.87 |
| 24,000 BTU | $39.74 | $31.80 | $26.50 |
Questions
FAQ
Is a mini split cheaper to run than a window AC?
Usually, yes. At the US average rate of 18.4¢/kWh and 8 hours a day, a 12,000 BTU mini split at SEER2 20 averaging 60% power costs an estimated $15.90 a month. A 12,000 BTU window unit at CEER 11 running its compressor the same 8 hours costs about $48.18.
What does a mini split cost to heat in winter?
In New York at 25.0¢/kWh, a 12,000 BTU head (HSPF2 8.5) heating 10 hours a day at a modulation of 0.7 averages 988 W and costs an estimated $74.12 a month. Switch the mode to Heat and pick your state for your number.
How much does it cost to run a mini split 24/7?
At the US average rate, a 12,000 BTU SEER2 20 head cooling around the clock at 60% average power uses 8.64 kWh a day, about $1.59 a day or $47.69 a month. In practice it runs well below maximum overnight.
What modulation factor should I use?
0.6 is a middle-of-the-road default. Use 0.4–0.5 for mild days and a well-sized unit, and 0.7–1.0 for extreme heat or cold, or a unit that's too small for the room.
Does a higher SEER2 always pay off?
Higher SEER2 lowers cooling watts in proportion: SEER2 20 draws 25% less than SEER2 15 for the same BTU. Whether that difference pays back the price gap depends on your rate and hours. Use Compare mode to see the dollars per month.
2026 note: The federal 25C and 25D tax credits ended for installations after Dec 31, 2025. Our numbers use 2026 rules. State rebates, HEAR/HOMES programs and utility programs may still apply.
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