Productive ToolboxAir Conditioner Power Calculator
Calculate AC power consumption in watts, monthly electricity cost, and required generator size from tonnage and EER/SEER rating.
Air Conditioner Power Calculator
Calculate AC electricity consumption and cost. Get instant estimates for daily, monthly, and yearly usage with real-time calculations.
Actions
AC Specifications
1 Ton = 12,000 BTU/h of cooling — not the power it draws
From the energy label (BTU/h per W). Typical EER: 8–10 older units, 11–13 modern, 14+ inverter. Use 10 if unknown.
Check your electricity bill for exact rate
Used for the current draw only; it does not change energy or cost.
Common AC Types
Next step
Related tools
What Is an Air Conditioner Power Calculator?
This air conditioner power calculator works out how many watts an AC draws from its capacity in tons and its EER or SEER rating (or from the power input on its label), then turns that into daily, monthly and yearly kWh and running cost at your own electricity tariff and currency.
The answer to "how many watts does a 1.5 ton AC use?" depends mostly on efficiency: at 18,000 BTU/h a unit rated EER 8 draws about 2,250 W, while one rated EER 14 draws about 1,290 W. Hours of use matter just as much for the bill, so both are inputs you can change and compare.
How AC Power Consumption Is Calculated
Core Formulas
Power (W) = Capacity (BTU/h) ÷ EER
Monthly kWh = (Power ÷ 1000) × Hours/Day × Days/Month
Monthly Cost = Monthly kWh × Rate ($/kWh)
Generator (rule of thumb) ≈ Running Watts × 2.5 for start-up surge
Example: 1.5 ton (18,000 BTU/h) ÷ EER 10 = 1,800W
1.8 kW × 8h × 30 days × $0.12 = $51.84/month
- 1 ton = 12,000 BTU/h cooling capacity (fixed conversion, all regions)
- EER — measured at peak conditions (95°F outdoor); lower EER = more watts per BTU
- SEER — seasonal average; convert to EER by multiplying SEER × 0.875 for peak-condition estimate
- Generator sizing — uses 2.5× running wattage to handle AC compressor startup surge
- Inverter ACs — variable speed compressor; actual consumption varies 30–100% of rated power depending on load
How to Use the Air Conditioner Power Calculator
Step-by-Step Guide
- 1Enter AC Capacity: Choose a capacity in tons (1 ton = 12,000 BTU/h) or switch to watts if you know the unit's power input from its label.
- 2Enter EER or SEER Rating: Type the EER or SEER from the product label. Typical range: 8–10 for older units, 12–14 for modern units, 16–22 for premium inverter ACs. Use 10 if unknown.
- 3Set Daily Hours and Days per Month: Enter how many hours per day the AC runs and how many days per month (typically 30). This drives monthly energy and cost calculations.
- 4Enter Your Electricity Rate: Type your electricity cost per kWh from your bill and choose your currency; rates vary widely between countries and suppliers.
- 5Read the Results: The calculator shows the running power, cooling capacity in BTU/h and kW, daily, monthly and yearly energy use in kWh, the monthly and yearly cost, and the current draw at the supply voltage you choose (120, 208, 230 or 240 V).
What This Calculator Provides
- ✓Running power from capacity in tons and an EER or SEER rating
- ✓Or start from the unit's power input in watts
- ✓Daily, monthly and yearly energy use (kWh)
- ✓Monthly and yearly cost at your own tariff and currency
- ✓Current draw at 120, 208, 230 or 240 V
- ✓Cooling capacity in BTU/h and kW
- ✓Energy-saving tip for your rating
- ✓Your inputs are not collected or stored
Worked Examples
Monthly Electricity Bill Estimation
A homeowner in Texas has a 1.5 ton mini-split (EER 11) running 10 hours/day during summer. They enter 1.5 tons, EER 11, 10 hours, 30 days, and $0.15/kWh. The calculator returns: 1,636W running load, 16.4 kWh/day, 491 kWh/month and about $73.60/month in electricity. Cutting the run time to 8 hours a day brings it to 393 kWh and about $58.90 — saving roughly $14.70 a month.
Comparing Inverter vs Non-Inverter AC
A buyer is deciding between a basic 1.5 ton unit (EER 9) and an inverter model (SEER 18) that costs $1,000 more. They run the calculator for each at 8 hours/day, 180 days/year, $0.16/kWh. Basic unit: 2,000W × 8h × 180 = 2,880 kWh/year, about $461/year. Inverter at SEER 18 (≈EER 15.75): 1,143W × 8h × 180 = 1,646 kWh, about $263/year. The annual saving of about $198 pays back the $1,000 premium in roughly 5 years.
Solar System Sizing for AC Load
A homeowner wants solar panels to offset a 1 ton AC running 6 hours/day. The AC at EER 11 draws 1,091W. Daily energy: 1.091 kW × 6h = 6.55 kWh/day. Accounting for inverter losses (90% efficiency) and panel output at their location (5 peak sun hours): panels needed = 6.55 ÷ 0.9 ÷ 5 = 1.46 kW of panel capacity. The homeowner installs a 1.6 kW (4 × 400W) solar array and a 10 kWh battery for evening use.
AC Power Consumption Reference Tables
Watts by Tonnage & EER
| Capacity | EER 8 | EER 10 | EER 12 | EER 14 |
|---|---|---|---|---|
| 0.75 ton / 9,000 BTU | 1,125W | 900W | 750W | 643W |
| 1 ton / 12,000 BTU | 1,500W | 1,200W | 1,000W | 857W |
| 1.5 ton / 18,000 BTU | 2,250W | 1,800W | 1,500W | 1,286W |
| 2 ton / 24,000 BTU | 3,000W | 2,400W | 2,000W | 1,714W |
| 2.5 ton / 30,000 BTU | 3,750W | 3,000W | 2,500W | 2,143W |
| 3 ton / 36,000 BTU | 4,500W | 3,600W | 3,000W | 2,571W |
Monthly Cost (8h/day, $0.12/kWh)
| Capacity | EER 10 | EER 12 | EER 14 |
|---|---|---|---|
| 1 ton | $34.56 | $28.80 | $24.69 |
| 1.5 ton | $51.84 | $43.20 | $37.03 |
| 2 ton | $69.12 | $57.60 | $49.37 |
| 2.5 ton | $86.40 | $72.00 | $61.71 |
| 3 ton | $103.68 | $86.40 | $74.06 |
* Assumes full-load operation. Inverter ACs typically consume 40–70% of rated watts at average loads.
Frequently Asked Questions
How many watts does a 1 ton AC use?
A 1 ton AC (12,000 BTU/h) consumes 12,000 ÷ EER watts. At EER 10: 1,200W. At EER 12: 1,000W. At EER 8 (older unit): 1,500W.
How many watts does a 1.5 ton AC use?
A 1.5 ton AC (18,000 BTU/h) consumes 18,000 ÷ EER watts. At EER 10: 1,800W. At EER 12: 1,500W. At EER 14: 1,286W.
What size generator is required for a 1.5 ton AC?
A 1.5 ton AC at 1,800W running load requires a generator rated at least 3 kVA to handle startup surge (2.5× running = 4,500W peak). A 5 kVA unit is recommended if running other loads simultaneously.
How do I calculate monthly electricity cost for an AC?
Monthly cost = (Watts ÷ 1000) × hours/day × days/month × rate/kWh. Example: 1,800W × 8h × 30 days × $0.12 = $51.84/month.
What is the difference between EER and SEER?
EER is measured at one standard peak-condition test point. SEER is the seasonal average across varying temperatures — always higher than EER for the same unit. For generator and circuit sizing, use EER. For annual cost estimation, use SEER. Convert: EER ≈ SEER × 0.875.
How many tons of AC do I need?
Approximately 20 BTU/h per square foot under standard conditions. A 400 sq ft room needs ~8,000 BTU/h (0.67 ton, round up to 1 ton). High ceilings or west-facing windows add 20–30% to the estimate.
What is the power consumption of a 2 ton AC?
A 2 ton AC (24,000 BTU/h) at EER 10 consumes 2,400W. At EER 12: 2,000W. Monthly cost at 8h/day, $0.12/kWh: EER 10 = $69.12; EER 12 = $57.60.
What is BTU and how does it relate to tons?
1 ton = 12,000 BTU/h. Common conversions: 0.75 ton = 9,000 BTU/h; 1.5 ton = 18,000 BTU/h; 2 ton = 24,000 BTU/h; 2.5 ton = 30,000 BTU/h; 3 ton = 36,000 BTU/h.
How do I size a circuit breaker for an AC?
Divide running watts by supply voltage to get running amps, then multiply by 1.25 (NEC continuous load factor). A 1.5 ton AC at 1,800W on 240V: 1,800 ÷ 240 = 7.5A × 1.25 = 9.4A — a 15A breaker is correct.
Is my data private when using this calculator?
Yes. We do not collect or store what you enter.
Related Tools
Energy Consumption Calculator
Calculate energy usage in kWh.
Electric Bill Calculator
Estimate electricity bill based on usage.
Fan Power Consumption Calculator
Estimate power used by fans.
Room Lighting Calculator
Calculate number of lights needed.
Electric Motor Power Calculator
Calculate motor power requirements.
RF Power Calculator
Calculate RF signal power.
Power Loss Calculator
Calculate losses in electrical systems.
Power Density Calculator
Calculate power per unit area.
Power Supply Calculator
Determine PSU requirements.
Power Calculator (Electrical)
Compute electrical power (P = VI).
Power Factor Calculator
Compute power factor in AC systems.
Real Power Calculator
Calculate real power in AC circuits.