aircon calculator

What this aircon calculator helps you do

Buying an air conditioner can feel confusing because brands use different labels: BTU, tonnage, horsepower (HP), inverter, and efficiency ratings. This calculator gives you a practical estimate of two things:

• Recommended cooling capacity based on room size, height, sunlight, and occupancy.
• Estimated monthly operating cost based on your local electricity rate and daily usage.

It is designed for quick planning, especially if you are deciding between two nearby models (for example, 9,000 BTU vs 12,000 BTU).

How the calculation works

1) Cooling capacity estimate (BTU/hr)

The calculator starts with room floor area and scales for ceiling height. Then it adds occupant heat load and applies environment multipliers for sun exposure and climate.

Where occupant load adds approximately 600 BTU/hr for each person above 2.

2) Energy and monthly bill estimate

After BTU is estimated, power draw is approximated from EER (Energy Efficiency Ratio):

Quick guidance on interpreting results

• If your recommended BTU is near a standard boundary, choose the next size up rather than down.
• Oversizing a little is usually safer than undersizing in hot climates.
• If humidity is high, inverter models often maintain better comfort with lower cycling stress.
• Use the monthly cost number for budgeting, not exact billing prediction.

Common room scenarios

Bedroom (small to medium)

Bedrooms usually have lower occupancy and moderate internal heat. If the room receives little afternoon sun, you can often stay near the lower end of the recommended range.

Living room

Living rooms often need larger units due to frequent occupancy changes, TVs/electronics, and door openings. If you entertain guests often, consider a buffer in BTU.

Home office

Computers and monitors add heat continuously. In sunny rooms, this combination can raise cooling demand more than expected. A higher-efficiency inverter unit can reduce long-term power cost.

How to reduce aircon electricity cost

• Set thermostat to a realistic comfort point (e.g., 24–26°C).
• Keep filters clean; clogged filters increase energy use.
• Seal gaps around doors/windows and use blinds on west-facing windows.
• Use ceiling fans to improve comfort and allow a higher setpoint.
• Schedule operation with timers or smart controls.

Important limitations

This tool gives a planning estimate. Professional HVAC sizing can include insulation quality, glass area, appliance load, air leakage, and building orientation. If you are cooling a large space, a top-floor room with intense sun, or a business area with many occupants, consult a qualified technician before purchase.