Loading page
About this tool
Work out when each air purifier or AC filter is actually due, date the next change, and add up the yearly filter and electricity cost.
The Home Air Filter Reminder converts a filter's dual rating — so many running hours or so many months, whichever comes first — into a real replacement date for your usage, and totals what the appliance costs to run for a year. Filter life is shortened by a loading factor built from the CPCB National AQI band outside plus indoor sources like pets, indoor smoking and nearby construction. For purifiers it also checks size against AHAM's two-thirds rule, where CADR in CFM should be at least two-thirds of the room's floor area for an 8 ft ceiling.
Open Home Air Filter Reminder on AltFTool — it loads instantly in your browser.
Pick the 'Appliance' — Room air purifier or Split or window air conditioner — and set 'Hours run per day', 'Typical outdoor air quality' (the CPCB bands from Good to Severe) and 'Power draw (watts)'.
Tick anything under 'Indoor sources that clog filters faster' — pets, smoking or incense, construction, open-kitchen frying — and give each filter a date under 'When was each filter last changed or washed?'.
Read the yearly cost with the 'Filter schedule' table giving the interval in days, the next-due date and cost per filter, plus the AHAM two-thirds CADR check on a purifier; 'Copy plan' saves the summary.
The tool shows whether running hours or calendar age is what actually ends the filter's life.
Enter the last change and get the exact next-due date for every filter in the unit.
Filters and electricity are added together, so the cheap purifier with expensive cartridges stops looking cheap.
Manufacturers typically rate a true HEPA filter at about 8,760 running hours or twelve months, whichever comes first. In cities where the AQI sits in the poor or very poor band, expect that to fall to roughly eight and six months respectively, because loading depends on particle concentration, not just hours.
Wash a split or window AC's mesh filter about every 30 days of use, or roughly every 150 running hours, and more often with pets or a dusty roadside. A clogged mesh restricts airflow, which drops cooling output and raises the compressor's running cost.
Use AHAM's two-thirds rule: for an 8 ft ceiling, the CADR in CFM should be at least two-thirds of the room's floor area in square feet, which gives about five air changes an hour. A 150 sq ft room needs roughly 100 CFM at 8 ft, or about 125 CFM if the ceiling is 10 ft.
No — washing a true HEPA filter ruptures the fibre matrix and destroys its efficiency, even though it looks clean afterwards. Only pre-filters and AC mesh filters are designed to be rinsed; activated carbon filters are also single-use because their pore structure saturates rather than clogs.