The short answer

An air purifier’s electricity cost depends on average input at each speed and its operating hours, or representative measured kWh. Filter-set cost and replacement interval add a separate budget. Compare CADR, speed, noise and room suitability alongside cost; fewer watts alone do not establish better air cleaning.

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Match power to the operating speed

A purifier may spend part of a day at a higher speed and the rest at a quieter setting. Price each non-overlapping period using average input watts. Automatic operation can change draw; a measured complete-day sample may represent that particular environment more closely than a fixed rating.

ENERGY STAR’s criteria distinguish power, clean-air delivery and filter information. Retain those distinctions in a cost comparison. A maximum-speed clean-air delivery rate does not describe every quieter setting.

A two-mode electricity example

The following is an illustrative power scenario, not measurements of a model:

Daily mode Average input Time Daily energy
Higher speed 40 W 8 hours 0.32 kWh
Lower speed 10 W 16 hours 0.16 kWh

The total is 0.48 kWh/day. For one appliance over 365 use days at an assumed $0.20/kWh, electricity is 175.2 kWh and $35.04. The modes cover 24 hours; an additional standby period would overlap this scenario and must not be added.

Keep the filter budget separate

Assume a full replacement-filter set costs $40 and the entered replacement interval is 12 calendar months. The annual accrual is $40 × 12 ÷ 12 = $40, making the combined electricity and filter budget $75.04 for this 365-day scenario.

A six-month interval instead budgets $80/year for filter sets. That interval is an assumption requiring the product’s instructions and actual conditions, not a universal recommendation. Dust, filter type and runtime can change replacement needs.

Electricity use days and calendar budget days are separate. For 90 electricity use days and a 365-day filter budget, the electricity scenario is $8.64 while filter accrual remains $40 under the entered interval. A prorated budget is not a claim that a new set must be bought during that exact period. Initial filters included in a purchase, spares already held and discrete replacement dates can change cash spending.

Compare equivalent cleaning context

Retain the CADR value, its unit, pollutant and tested speed, together with relevant noise and room information. A lower-cost operating mode may provide less airflow. The calculator records optional performance context alongside costs; it does not infer CADR from watts, size a room or provide health advice.

Use similar conditions if you compare measured routines before and after a setting change. A short test in a clean room is not automatically representative of a dusty period with automatic high-speed operation.

Preserve the energy boundary

A complete-day measurement already includes any captured standby, automatic speed changes and display power. Do not add mode estimates to it. Quantity assumes identical devices on the same schedule and a filter price per device.

Keep the model, replacement-filter code and source prices in the saved report. A blank filter budget stays explicitly excluded. The journal can retain repeated observations with their settings and conditions before you choose a representative daily average.

Distinguish a filter budget from cash purchases

With an illustrative $40 annual replacement-set accrual, a 30-calendar-day budget allocates $40 × 30 ÷ 365 = about $3.29. That does not mean a filter can be bought for $3.29 or that a replacement is due in those 30 days.

An initial filter included with a new appliance, spares already held and an actual replacement date can make cash spending differ from accrual. Keep those facts separately rather than treating a prorated amount as a purchase schedule.

Keep performance labels with each mode

Record which speed and pollutant a declared CADR describes. ENERGY STAR’s criteria distinguish clean-air delivery, operating power and filter information. A high-speed performance figure must not be silently paired with a low-speed electricity input.

For automatic operation, a measured daily sample captures one environment and routine. Retain the room context and conditions before comparing another period. A low cost estimate does not certify air-cleaning effectiveness or provide a health outcome.