The short answer
Yes, for most homes: run it continuously on auto or a low setting. Electricity for a typical 20 to 60 W unit on low is a few dollars a month; the bigger running cost is replacement filters.
Why continuous
Pollen, dust, pet dander and cooking particles enter a room constantly. When a purifier is switched off, levels climb back within hours. Running it all the time on a quiet setting keeps the room clean rather than catching up.
Electricity
| Power draw | Per day | Per month |
|---|---|---|
| 10 W | 0.24 kWh | about $1.20 |
| 30 W | 0.72 kWh | about $3.50 |
| 60 W | 1.44 kWh | about $7 |
Most purifiers draw well under their maximum on low or auto. The maker's wattage figure is usually the highest speed.
Filter life
Running 24/7 uses up filters faster than occasional use, and makers' intervals usually assume all-day operation. Use the unit's filter indicator; replace sooner in smoky or pet-heavy homes.
Products mentioned
Questions readers ask
Is it safe to run an air purifier all night?
Yes; mechanical HEPA purifiers are designed for continuous use. Avoid ozone-generating devices.
Does auto mode save energy?
Yes; it runs low when the air is clean and speeds up only when the sensor detects particles.