Air Conditioner Power Calculator

Step-by-Step Guide

1. 1Enter AC capacity: Input your air conditioner's capacity in tons (e.g., 1, 1.5, 2) or BTU/h (e.g., 12000, 18000). Both input methods are supported — select whichever matches your unit's spec sheet or nameplate.
2. 2Enter the EER or SEER rating: Type the unit's EER (Energy Efficiency Ratio) or SEER from the product label or datasheet. Typical range: 8–10 for older non-inverter units, 12–14 for modern standard units, 16–22 for premium inverter ACs. If unknown, use 10 as a conservative estimate.
3. 3Set daily operating hours and days per month: Enter how many hours per day the AC runs and how many days per month — typically 30. This drives the monthly energy consumption and cost calculation.
4. 4Enter your electricity rate: Type your local electricity cost per kWh. This appears on your electricity bill. Common ranges: $0.10–0.15/kWh in the US, ₹5–8/kWh in India, ৳7–10/kWh in Bangladesh.
5. 5Read power, energy, and cost results: The calculator returns running wattage, monthly kWh consumption, monthly electricity cost, required circuit breaker size, and recommended generator/inverter kVA — all updated instantly as you change inputs.
6. 6Use room sizing mode to find required tonnage: Switch to room sizing mode, enter room dimensions and sun exposure level, and the calculator returns the required AC capacity in tons and BTU/h for your space.

What This Calculator Provides

• ✓Running wattage from tons and EER/SEER
• ✓Monthly kWh energy consumption
• ✓Monthly electricity cost in your currency
• ✓Annual energy cost
• ✓Required circuit breaker size
• ✓Recommended generator/inverter kVA
• ✓Tons ↔ BTU/h ↔ kW conversion
• ✓Room sizing mode (sq ft → required tons)
• ✓EER vs SEER comparison
• ✓Side-by-side comparison of two AC units
• ✓100% browser-based — no data sent to any server
• ✓No signup required

Pro Tips

• 💡Use the actual nameplate wattage (input power, not output cooling capacity) if it is printed on the AC unit or in the manual — it is more accurate than calculating from BTU/EER. The BTU/EER method gives a theoretical value; nameplate input watts give the real-world consumption figure.
• 💡For inverter ACs, the rated wattage is the maximum (compressor at full speed). Actual average consumption is typically 40–70% of rated input, depending on ambient temperature and thermostat setpoint. Use 60% of rated watts as a conservative average for monthly cost estimation.
• 💡When sizing a generator, always use 2.5–3× the running wattage for the surge calculation. AC compressors draw 3–6× rated current at startup for 0.5–2 seconds. A generator that cannot handle this surge will stall even if its continuous rating exceeds the running load.
• 💡Higher EER saves more money in hot climates with long cooling seasons. In a climate where the AC runs 6 months/year, going from EER 10 to EER 14 on a 1.5 ton unit saves approximately 400 kWh/year — worth $40–60 at typical residential electricity rates.
• 💡For circuit breaker sizing, divide the running wattage by the supply voltage to get running amps, then multiply by 1.25 for the 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.

Common Mistakes to Avoid

• ✕Don't confuse cooling capacity (BTU/h or tons) with power consumption (watts or kW). They are related through EER but are not the same thing. A 1.5 ton AC does not consume 1.5 kW — it consumes 1,500–2,250W depending on efficiency, while delivering 18,000 BTU/h of cooling.
• ✕Don't use SEER directly in the BTU/EER formula without converting. SEER is a seasonal average always higher than EER. Using SEER instead of EER in the Power = BTU/EER formula will underestimate peak wattage. For generator and circuit sizing, always use EER or convert: EER ≈ SEER × 0.875.
• ✕Don't undersize a generator by using only running watts. The startup surge of an AC compressor can trip a generator sized only to its running load. Always apply a 2.5–3× surge multiplier when selecting backup power equipment.
• ✕Don't assume a bigger AC cools faster. An oversized AC cycles on and off too quickly, failing to dehumidify the room properly and wearing out the compressor faster. Use the room sizing mode to select the correct capacity, not the largest available.
• ✕Don't calculate monthly cost from the nameplate BTU rating alone. That rating is the cooling output, not the electrical input. You need the EER to convert BTU/h to watts, then multiply by operating hours and electricity rate. Skipping EER always overstates or understates the actual cost.