What It CostsWhat does an air purifier cost to run?
Air purifier running cost
$3.73 a month ≈ $44.68 a year
That is 0.72 kWh a day · $0.12 a day · $0.0051 an hour while it runs
- Electricity used a year
- 263 kWh
- Cost a week
- $0.86
- Cost a year
- $44.68
Wattage roughly triples between the lowest and highest fan speed. If the machine is on auto and the air is clean, it is drawing far less than the label says.
One thing off the bill each month
MonthlyOne appliance a month worth measuring or changing, and what it does to the yearly total. No tariff pitches, no prices — the numbers that stay true.
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How much does it cost to run an air purifier 24/7?
About $3.73 a month for a typical 30 W purifier left on permanently — £5.48 at £0.25 per kWh, €7.67 at €0.35. Over a year that is roughly $45, and it is the smaller half of what the machine costs you.
The filters cost more than the electricity. A true-HEPA set is $40 to $90 and wants changing every 6 to 12 months, plus a carbon pre-filter two or three times a year. Budget $60 to $150 a year for filters against $45 for power — so anyone comparing purifiers on wattage alone is optimising the cheaper line.
Fan speed is the lever on both. A purifier on high might draw 55 W and on its lowest setting 8 W, and running it hard also loads the filter faster. The efficient answer is to size the machine for the room — a purifier whose clean-air delivery rate suits the space will hold it on a low speed — rather than to buy a small one and run it flat out.
The electricity, and then the number people forget until the filter light comes on.
| Setting | Watts | A month, on 24/7 | A year |
|---|---|---|---|
| Night / sleep | 10 W | $1.24 | $14.89 |
| Low | 18 W | $2.24 | $26.81 |
| Auto, average | 30 W | $3.73 | $44.68 |
| Medium | 40 W | $4.97 | $59.57 |
| High | 55 W | $6.83 | $81.91 |
| Large unit, maximum | 100 W | $12.42 | $148.92 |
Against any row in that table, a $70 HEPA filter changed once a year is the larger expense — and unlike the electricity, skipping it does not save money, it just stops the machine working.
Frequently asked questions
How much electricity does an air purifier use?
Between 8 and 100 watts depending on size and fan speed. A small bedroom unit on low is 8 to 15 W, a mid-size room unit on auto averages 25 to 35 W, and a large model on its highest setting can reach 100 W. Running 24 hours a day at 30 W uses about 263 kWh a year.
Is it expensive to run an air purifier all the time?
No — around $45 a year at $0.17 per kWh for a typical unit, which is less than a light left on. The expense is the filters, which run $60 to $150 a year. Continuous running is also what the machine is designed for: purifiers clean air continuously and starting from scratch each evening means breathing dirty air all day.
How often do air purifier filters need changing?
HEPA filters every 6 to 12 months, carbon pre-filters every 3 to 6 months, and washable pre-filters every few weeks with a vacuum. Heavy use, pets, smoke or wildfire season shortens all of those. A filter left in past its life does not just stop working — it restricts airflow, so the fan works harder for less clean air.
Does running it on a lower speed save money?
Yes, on both counts: fan power scales steeply with speed, and less air through the filter means the filter lasts longer. The trade-off is clean-air delivery. If a room needs five air changes an hour, running a small machine on low will not deliver them — that is a sizing problem, not a settings one.
Should I leave an air purifier on at night?
Yes, if the machine is quiet enough. A bedroom is where you spend eight uninterrupted hours breathing, so it is the room where a purifier does the most good. Most units have a night mode that drops the fan and turns off the display; on that setting a typical purifier is 8 to 15 W, about $0.03 for the night.
Do ionisers and UV models use less power?
The ioniser or UV stage itself uses very little, but it is not a substitute for the fan and filter, which is where both the power and the cleaning happen. Ionisers can also produce ozone, which is a lung irritant; California maintains a list of air cleaners that meet its ozone limit, and it is worth checking before buying one.
How we calculate this
Worked example
With Power it draws (watts) 30, Hours a day 24, Days a week 7, Country United States (USD), Your price per kWh 0.17, this page works out $3.73 a month ≈ $44.68 a year. That is 0.72 kWh a day · $0.12 a day · $0.0051 an hour while it runs
- Electricity used a year263 kWh
- Cost a week$0.86
- Cost a year$44.68
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