A 12,000 BTU mini split uses 400–1,200 watts depending on compressor load, consuming 3.2–9.6 kWh per day when running 8 hours. Over a full cooling season, that's 500–900 kWh — roughly $85–$153 at the national average electricity rate of $0.17/kWh. Inverter-driven mini splits average 30–50% less electricity than these maximum wattage figures because they modulate compressor speed rather than running at full power.
The exact electricity consumption depends on five factors: the unit's BTU capacity, its SEER2 efficiency rating, how many hours per day it runs, the temperature differential between your thermostat setting and outdoor temp, and your local electricity rate. Below you'll find real wattage data for every common mini split size, plus worked examples showing actual monthly kWh usage in different climates.
Mini Split Wattage by Size
Every mini split has a rated wattage that represents maximum power draw at full compressor speed. But inverter mini splits rarely run at maximum — they typically operate at 30–70% capacity once a room reaches the set temperature. The table below shows both rated (maximum) and typical (average) wattage.
Cooling Mode Wattage
| Unit Size (BTU) | Tonnage | Rated Watts (Max) | Typical Watts (Avg) | Startup Watts |
|---|---|---|---|---|
| 6,000 | 0.5 ton | 500–600 | 200–350 | 800–1,000 |
| 9,000 | 0.75 ton | 600–900 | 250–500 | 1,000–1,400 |
| 12,000 | 1 ton | 800–1,200 | 350–700 | 1,200–1,800 |
| 15,000 | 1.25 ton | 1,000–1,500 | 500–900 | 1,500–2,200 |
| 18,000 | 1.5 ton | 1,200–1,800 | 600–1,100 | 1,800–2,700 |
| 24,000 | 2 ton | 1,800–2,500 | 900–1,500 | 2,500–3,500 |
| 30,000 | 2.5 ton | 2,200–3,000 | 1,100–1,800 | 3,000–4,200 |
| 36,000 | 3 ton | 2,800–3,800 | 1,400–2,300 | 3,800–5,000 |
Heating Mode Wattage
Mini splits in heating mode typically consume 10–30% more electricity than in cooling mode for the same BTU output, because the outdoor unit must work harder to extract heat from cold air. At extremely cold temperatures, supplemental electric resistance heating strips may kick in, dramatically increasing wattage.
| Unit Size (BTU) | Heating Watts (Mild, 40°F) | Heating Watts (Cold, 20°F) | Heating Watts (Extreme, 0°F) |
|---|---|---|---|
| 9,000 | 300–600 | 600–1,000 | 900–1,500 |
| 12,000 | 400–800 | 800–1,400 | 1,200–2,000 |
| 18,000 | 600–1,200 | 1,200–2,000 | 1,800–3,000 |
| 24,000 | 900–1,600 | 1,600–2,800 | 2,400–4,000 |
| 36,000 | 1,400–2,400 | 2,400–4,000 | 3,600–6,000 |
Why heating uses more watts in colder weather: As outdoor temperature drops, the temperature differential between the refrigerant and outdoor air shrinks, making it harder to extract heat. The compressor must work harder (higher speed, higher pressure), drawing more electricity. A mini split heating at 40°F might use 400 watts; the same unit heating at 0°F could use 1,200+ watts — triple the consumption for lower heat output.
How to Calculate Your Mini Split's kWh Usage
The formula is straightforward:
Daily kWh = (Average watts × Hours of operation) ÷ 1,000
Monthly kWh = Daily kWh × 30
Annual kWh = Monthly kWh × Months of use
Worked Example 1: 12K BTU in Houston, TX (Hot Climate)
A homeowner runs a 12,000 BTU mini split (SEER2 20) in a Houston bedroom. Summer conditions: outdoor 95°F, indoor setpoint 72°F, unit runs ~14 hours/day.
- SEER2 20 means the unit delivers 20 BTU of cooling per watt-hour
- At full load: 12,000 BTU ÷ 20 SEER2 = 600 watts
- Inverter operating at ~60% average capacity: 600 × 0.6 = 360 watts average
- Daily kWh: (360 × 14) ÷ 1,000 = 5.04 kWh/day
- Monthly kWh: 5.04 × 30 = 151.2 kWh/month
- Cooling season (May–October, 6 months): 151.2 × 6 = 907 kWh/year
- Annual cooling cost at $0.14/kWh (Texas avg): $127/year
Worked Example 2: 18K BTU in Portland, OR (Mild Climate)
A 500 sq ft living room with an 18,000 BTU mini split (SEER2 22). Portland summer: outdoor 85°F, indoor setpoint 74°F, unit runs ~8 hours/day.
- At full load: 18,000 ÷ 22 = 818 watts
- Inverter at ~40% capacity (small temp differential): 818 × 0.4 = 327 watts average
- Daily kWh: (327 × 8) ÷ 1,000 = 2.62 kWh/day
- Monthly kWh: 2.62 × 30 = 78.5 kWh/month
- Cooling season (June–September, 4 months): 78.5 × 4 = 314 kWh/year
- Annual cooling cost at $0.12/kWh (Oregon avg): $37.70/year
Worked Example 3: 24K BTU Heating in Minneapolis, MN (Cold Climate)
A 24,000 BTU Mitsubishi Hyper-Heat in a 700 sq ft finished basement. January conditions: outdoor 10°F average, indoor setpoint 68°F, unit runs ~18 hours/day.
- At 10°F, the unit produces ~18,000 BTU of heating (reduced capacity)
- Heating power draw at 10°F: approximately 2,200 watts average
- Daily kWh: (2,200 × 18) ÷ 1,000 = 39.6 kWh/day
- Monthly kWh: 39.6 × 30 = 1,188 kWh/month
- Cost at $0.15/kWh (Minnesota avg): $178/month
- Full heating season (October–April, 7 months, varying intensity): ~5,500 kWh
- Annual heating cost: ~$825/year
Worked Example 4: Multi-Zone 36K BTU in Atlanta, GA
A 36,000 BTU 3-zone system (12K + 12K + 12K) serving living room, master bedroom, and office. Summer in Atlanta: outdoor 92°F, setpoint 73°F. Not all zones run simultaneously — average 2 zones active for 10 hours/day.
- Two 12K zones at SEER2 18: each draws ~667 watts at full load
- Average load per zone (~55% capacity): 667 × 0.55 = 367 watts
- Two zones running: 367 × 2 = 734 watts average
- Daily kWh: (734 × 10) ÷ 1,000 = 7.34 kWh/day
- Monthly kWh: 7.34 × 30 = 220 kWh/month
- Cooling season (5 months): 1,100 kWh/year cooling
- Annual cooling cost at $0.14/kWh (Georgia avg): $154/year
Mini Split vs. Other HVAC: Electricity Usage Comparison
How does a mini split stack up against other cooling and heating methods? The differences are dramatic.
Cooling Comparison (Same 400 sq ft Room)
| System Type | Watts (Avg) | kWh/Day (8 hrs) | kWh/Month | Monthly Cost ($0.17) |
|---|---|---|---|---|
| Mini split 12K (SEER2 20) | 350–500 | 2.8–4.0 | 84–120 | $14–$20 |
| Window AC 12K (EER 12) | 1,000 | 8.0 | 240 | $41 |
| Portable AC 12K (EER 8) | 1,500 | 12.0 | 360 | $61 |
| Central AC 12K (SEER2 15) | 550–800 | 4.4–6.4 | 132–192 | $22–$33 |
Heating Comparison (Same 400 sq ft Room, 40°F Outdoor)
| System Type | Watts (Avg) | kWh/Day (12 hrs) | kWh/Month | Monthly Cost ($0.17) |
|---|---|---|---|---|
| Mini split 12K heat pump (HSPF2 10) | 400–700 | 4.8–8.4 | 144–252 | $24–$43 |
| Electric baseboard (1,500W) | 1,500 | 18.0 | 540 | $92 |
| Electric space heater (1,500W) | 1,500 | 18.0 | 540 | $92 |
| Electric furnace (5 kW, cycling) | 2,500 avg | 30.0 | 900 | $153 |
The heating comparison is where mini splits truly shine. A mini split heat pump delivers 2.5–4x more heat per watt than any electric resistance heater (baseboard, space heater, electric furnace). This is because a heat pump moves heat rather than creating it — for every 1 watt of electricity consumed, it delivers 2.5–4 watts of heat energy from outdoor air.
Factors That Increase Mini Split Electricity Usage
Understanding what drives consumption up helps you optimize performance and keep bills low.
| Factor | Impact on kWh | Why |
|---|---|---|
| Higher temperature differential | +30–100% | Unit works harder to bridge bigger gap |
| Poor insulation | +20–40% | Room gains/loses heat faster |
| Dirty filters | +5–15% | Restricted airflow forces higher compressor load |
| Dirty coils | +10–20% | Reduced heat transfer efficiency |
| Oversized unit | +10–25% | Short cycling wastes energy on startup/shutdown |
| Undersized unit | +15–30% | Unit runs at max capacity continuously |
| Sunny room (unshaded) | +10–20% | Solar heat gain adds to cooling load |
| Multiple occupants | +5–15% | Each person generates ~350 BTU/hr of body heat |
| Heat-generating equipment | +10–30% | Computers, ovens, dryers add to cooling load |
| Low SEER2 rating | +20–50% | Less efficient conversion of electricity to cooling |
How to Reduce Mini Split Electricity Usage
These practical steps can cut your mini split's electricity consumption by 20–40%:
Set temperature wisely. Every degree cooler (or warmer in heating mode) increases energy use by approximately 3–5%. Setting your AC to 76°F instead of 72°F saves roughly 12–20% on cooling costs with minimal comfort impact.
Clean filters every 2–4 weeks. A clogged filter is the single biggest efficiency killer. A dirty filter can increase electricity consumption by 5–15% and reduces the unit's cooling capacity, making it run longer to maintain temperature.
Use the timer and scheduling features. There's no reason to cool an empty room. Program the unit to power down when you leave and start cooling 15–30 minutes before you return. Most smart mini splits support scheduling through their app.
Run dry mode in humid conditions. In humid climates, switching to dry mode uses less electricity than cool mode while still removing moisture. Dry mode runs the compressor at minimum speed and the fan at the lowest setting, using 40–60% less power than cooling mode.
Shade the outdoor unit. An outdoor condenser operating in direct sunlight is 5–10% less efficient than one in shade. Plant bushes (keep 2+ feet of clearance) or install an awning. Never enclose the unit — it needs unrestricted airflow.
Improve room insulation. Adding weatherstripping, insulating window film, or thermal curtains reduces your room's heat gain/loss, meaning the mini split works less. A $50 investment in window film can save $30–$60 per year in electricity.
Annual Electricity Cost by State (12,000 BTU Mini Split, SEER2 20)
Electricity rates vary enormously by state. Here's what a 12K mini split costs to run annually in cooling mode across the most expensive and cheapest states:
| State | Avg Rate ($/kWh) | Annual Cooling kWh | Annual Cooling Cost | Annual Heating kWh | Annual Heating Cost |
|---|---|---|---|---|---|
| Hawaii | $0.37 | 650 | $241 | 200 | $74 |
| Connecticut | $0.30 | 550 | $165 | 700 | $210 |
| Massachusetts | $0.28 | 500 | $140 | 800 | $224 |
| California | $0.27 | 600 | $162 | 350 | $95 |
| New York | $0.24 | 550 | $132 | 750 | $180 |
| National Average | $0.17 | 600 | $102 | 600 | $102 |
| Florida | $0.15 | 900 | $135 | 200 | $30 |
| Texas | $0.14 | 850 | $119 | 400 | $56 |
| Georgia | $0.14 | 800 | $112 | 450 | $63 |
| Louisiana | $0.10 | 900 | $90 | 300 | $30 |
| Idaho | $0.10 | 400 | $40 | 700 | $70 |
Note: These figures assume moderate usage patterns typical for each climate. Florida and Texas have high cooling kWh because cooling seasons are long (7–9 months). Connecticut and Massachusetts have high heating kWh because heating seasons are long (6–7 months). States like California have moderate usage for both because coastal areas enjoy mild weather year-round.
Measuring Your Mini Split's Actual Electricity Usage
Want exact data rather than estimates? Here are three ways to measure real consumption:
Method 1: Kill-A-Watt meter ($25–$35). Works for 120V mini splits only. Plug the unit into the Kill-A-Watt, and it records cumulative kWh. After 24 hours or a week, you'll have precise consumption data. Limitation: most mini splits are 240V hardwired, so this only works for the few 120V models (typically 6K and 9K units).
Method 2: CT clamp energy monitor ($40–$80). Devices like the Emporia Vue or Sense clamp onto the dedicated circuit's wiring in your breaker panel and measure consumption continuously. Works with any voltage, provides real-time data via an app, and tracks usage over weeks and months. This is the best method for most homeowners.
Method 3: Smart circuit breaker ($80–$150). Replace your mini split's circuit breaker with a smart breaker (like Eaton or Leviton) that monitors energy consumption and reports to an app. Provides the most accurate data with automatic tracking and historical charts.
Method 4: Read your utility bill. If the mini split is the only significant load change in your home, compare utility bills before and after installation. The difference approximates the mini split's consumption. This method is rough but requires no equipment.
Key Takeaways
- A 12,000 BTU mini split uses 350–700 watts on average (rated maximum 800–1,200 watts) thanks to inverter modulation
- Daily consumption: 2.8–5.6 kWh for cooling (8 hours), 4.8–8.4 kWh for heating (12 hours)
- Monthly cost: $14–$43 for a single zone depending on climate, usage, and electricity rate
- Mini splits use 50–70% less electricity than window ACs or portable ACs for the same cooling capacity
- Heating efficiency is the biggest advantage — mini split heat pumps deliver 2.5–4x more heat per watt than electric resistance heaters
- Clean filters save 5–15% on electricity — this is the easiest efficiency win
- Your electricity rate matters enormously — the same unit costs $40/year in Idaho but $241/year in Hawaii