Inverter AC versus fixed-speed AC running cost

Start with comparable models

Use the exact model input or annual consumption for ACs of the required cooling capacity. Do not compare only the words inverter and fixed speed.

Keep the room scenario the same

Use the same hours, days, electricity rate, room heat and thermostat scenario when comparing two models.

Treat cycling as a scenario

An inverter model can change compressor output while a fixed-speed model cycles differently, but the real difference depends on the selected models and room conditions.

Use model evidence, not a category promise

‘Inverter’ describes the way compressor speed can be controlled; ‘fixed speed’ describes different cycling behaviour. Neither term supplies the model’s electrical input, annual energy or the room’s cooling load. Start with exact model labels or official product sheets and avoid a universal saving percentage.

Worked like-for-like scenarios

For illustration, Model A is entered at 1,300 W with a 0.55 operating factor and Model B at 1,200 W with a 0.70 factor. At eight hours for 30 days, A gives 1.3 × 0.55 × 8 × 30 = 171.6 kWh; B gives 201.6 kWh. The factors are hypothetical scenarios, not claims about inverter or fixed-speed products.

Why a lower nameplate watt can still mislead

A model may operate for a different fraction of the time or fail to meet the same cooling task in a different room. Oversizing, undersizing, high heat gain, set point and maintenance influence cycling and average draw. Compare equipment selected for the same required cooling load and conditions.

Measure after installation

Where safe and technically appropriate, use circuit-level energy data or meter readings across comparable weather and operating periods. Record room use and set point. Do not infer a category-wide saving from one home, and do not use a plug meter that is not rated for the appliance circuit.

Cost is the final, local step

After estimating kWh, apply the rate or slab treatment from the relevant bill. Fixed charges and account-specific lines may not change with the AC model, so keep energy-cost comparison separate from the total payable amount.

Fair comparison checklist

Select models capable of the same required cooling task, then copy each exact model’s energy evidence. Keep room conditions, hours, days, rate and calculation approach unchanged. If you use an operating factor, label it as an entered scenario and run more than one plausible value. The resulting table compares arithmetic under those assumptions; it does not certify one compressor type as cheaper in every home.

• Avoid retailer category averages with no model source.
• Separate energy charge from fixed bill lines.
• Use observed energy only from safe, comparable measurements.