“Running it 24/7” sounds expensive — like leaving the AC on all summer or the heater blasting. So when a purifier’s box says “run continuously for best results,” the question is natural: what’s that going to cost me?
The answer is pleasantly boring: less than a cup of coffee a month for most units. Here’s the real math.
The Electricity Math
The formula: watts × hours ÷ 1000 = kWh. Then × your rate (US average: ~16.6¢/kWh).
| Unit class | Typical wattage (normal speed) | Cost per month (24/7) |
|---|---|---|
| Compact (Core Mini, IKEA) | 5-15W | $0.60-1.80 |
| Budget (Core 300, Airmega 150) | 20-40W | $2.40-4.80 |
| Mid (Vital 200S, Winix 5500-2) | 30-50W | $3.60-6.00 |
| Large (Core 600S, Airmega 400) | 40-70W | $4.80-8.40 |
| Max speed on any big unit | 60-100W | $7.20-12.00 |
The headline: $2-6/month for 24/7 operation on normal speeds. That’s the same as a phone charging, or a modem. Electricity is a rounding error.
The Real Cost: Filters
Here’s what actually adds up — and it’s the number most buyers never check:
| Unit | Filter cost | Typical change | Yearly filter bill |
|---|---|---|---|
| Levoit Core 300 | ~$30 | 6-8 months | ~$50 |
| Levoit Vital 200S | ~$35 | 6-8 months | ~$55 |
| Winix 5500-2 | ~$40 | 6-12 months (washable carbon) | ~$50 |
| Coway Airmega 400 | ~$99 | 12 months | ~$99 |
| Dyson TP07 | ~$90-140 | 12 months | ~$90-140 |
| Rabbit Air MinusA2 | ~$80 | 12-24 months | ~$40-80 |
The honest total: a typical household running one mid-size purifier 24/7 spends $80-150/year — about $55-100 on filters and $30-50 on electricity. For the allergy relief and dust reduction you get, it’s among the cheapest health investments in the home.
The “Run It on Max” Trap
Max speed is the only setting that costs real money: 60-100W is $7-12/month — and it doesn’t clean meaningfully faster for normal use. The practical rule:
- Medium or auto: the default — 80-90% of the benefit, half the power
- Max: for events — smoke, cooking accidents, wildfire days
- Low: overnight in bedrooms — nearly free, still effective in a small room
Ways to Trim the Bill (If You Care)
- Use auto mode — most units with sensors idle on low when the air is clean
- Run medium instead of high — same air quality, half the power
- Choose cheap filters — a $30 filter unit beats a $100 filter unit over 5 years
- Don’t oversize — a too-big unit running on low in a small room wastes the price premium, not much power
- Vacuum the pre-filter monthly — clean pre-filters keep the main filter (and the fan) efficient
The Bottom Line
Running an air purifier 24/7 costs $2-6/month in electricity — genuinely trivial — and the real yearly bill is the filters, $50-150/year for most households. The honest takeaway: electricity shouldn’t factor into your 24/7 decision at all. If a purifier is worth having, it’s worth running continuously — the $30-100/year it costs is the price of consistently clean air, and it’s one of the cheapest health upgrades in the home. Use the cost calculator for your exact model and rates.
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Runs side-by-side purifier comparisons, long-term ownership reports, and filter cost analysis.
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