Mini split BTU & running cost calculator

Tell us about the room and we estimate the mini split size you need, then what it costs to run at a given SEER2 rating. Estimates from published rules of thumb, not a substitute for a Manual J load calculation. The reasoning behind every adjustment is in the sizing guide.

The room

Room size (sq ft) Ceiling height Climate

Hot, humid regions add 10 to 20 percent to the baseline. Size for August, not April.

Sun exposure Insulation People regularly in the room beyond two This is a kitchen

Running cost

Your electricity rate ($ per kWh)

US residential average was 18.8 cents per kWh in March 2026 per the EIA. Your bill has your real number.

Estimated full-load cooling hours per year

An assumption you control: hours per year the unit works at full output, or the equivalent spread over partial loads. Long hot summers push this up; mild climates pull it down.

SEER2, unit A

SEER2, unit B

Recommendation

Estimated cooling load

Recommended unit size

Annual cooling energy @ unit A

Annual cost @ unit A

Annual cost @ unit B

Unit B saves per year

Sizing uses the 20 BTU per square foot baseline with published climate, ceiling, sun, insulation, and occupancy adjustments, rounded up to the next standard capacity. Cost assumes cooling only: BTU × hours ÷ (SEER2 × 1000) × rate. Estimates, not a Manual J load calculation. Electrical work belongs to a licensed pro; see the wiring guide.

Browse the mini split guides →