Air purifiers are not heavy electricity users. They're fans with filters — motors that move air, not heat it. A typical model uses 10-60W depending on fan speed, which puts them in the same bracket as a desk lamp or a Wi-Fi router, well below a vacuum cleaner, kettle or tumble dryer.
That said, an air purifier running continuously adds up. Here are the real numbers.
Wattage by Model and Speed
Most manufacturers publish wattage in their specs, usually at maximum speed. The sleep-mode figure is often significantly lower.
| Model | Sleep mode | Medium | Max |
|---|---|---|---|
| Levoit Core 300 | 7W | 12W | 22W |
| Levoit Core 400S | 8W | 25W | 45W |
| Blueair Blue Max 3250i | ~7W | ~15W | ~30W |
| Winix Zero S | ~8W | ~20W | ~52W |
| Philips 3000i AC3033 | ~7W | ~30W | ~55W |
| Coway Airmega 100 | ~5W | ~15W | ~33W |
These are approximate figures; actual consumption varies with ambient conditions and sensor-driven auto adjustments.
The Calculation
The formula is straightforward:
Cost = Watts ÷ 1,000 × Hours × Unit rate
The current UK unit rate (as of early 2026) is approximately 24.5p per kWh under the standard price cap. This changes quarterly; check your energy bill for your actual rate.
Usage Scenarios
Running on sleep mode overnight (8 hours)
Using the Levoit Core 300 at 7W sleep mode:
7W ÷ 1,000 × 8 hours × 24.5p = 0.014p per night
That's essentially free. Even at 24/7 on sleep mode:
7W ÷ 1,000 × 24 hours × 365 days × 24.5p = £15.02 per year
Running on medium speed for 8 hours a day
Using the Levoit Core 400S at 25W medium:
25W ÷ 1,000 × 8 × 24.5p = 4.9p per day = £17.88 per year
Running on medium speed 24 hours a day
25W ÷ 1,000 × 24 × 365 × 24.5p = £53.66 per year
Running on maximum speed 8 hours a day
45W ÷ 1,000 × 8 × 24.5p = 8.8p per day = £32.12 per year
Filter Replacement Costs
Electricity is only part of the annual running cost. Filter replacement is often the larger expense.
| Model | Replacement filter cost | Replacement interval | Annual cost |
|---|---|---|---|
| Levoit Core 300 | ~£25 | 6-8 months | ~£37 |
| Levoit Core 400S | ~£35 | 6-8 months | ~£52 |
| Blueair Blue Max 3250i | ~£30 | 12 months | ~£30 |
| Winix Zero S | ~£30 | 12 months | ~£30 |
| Philips 3000i AC3033 | ~£50 | 36 months | ~£17 |
| Coway Airmega 100 | ~£25 | 12 months | ~£25 |
The Philips 3000i is the outlier — high upfront cost, but the 36-month filter lifespan gives it the lowest annualised filter cost of any model here.
Total Annual Cost Comparison
Combining electricity (medium speed, 8 hours/day) and filter replacement:
| Model | Electricity/year | Filter/year | Total/year |
|---|---|---|---|
| Levoit Core 300 | ~£11 | ~£37 | ~£48 |
| Coway Airmega 100 | ~£11 | ~£25 | ~£36 |
| Blueair Blue Max 3250i | ~£15 | ~£30 | ~£45 |
| Winix Zero S | ~£18 | ~£30 | ~£48 |
| Levoit Core 400S | ~£18 | ~£52 | ~£70 |
| Philips 3000i AC3033 | ~£29 | ~£17 | ~£46 |
These figures assume medium speed for 8 hours a day. Running 24/7 on auto mode (which cycles between sleep and medium based on sensor readings) lands most people somewhere between the 8-hour and 24-hour calculations.
Tips for Reducing Running Costs
Use auto mode. A purifier with a PM2.5 sensor and auto mode runs on low power when the air is already clean and ramps up only when needed. This reduces average wattage significantly compared to running at a fixed medium setting.
Sleep mode overnight. The difference between sleep mode (7-8W) and medium (20-30W) over eight hours every night adds up to £20-30 per year. If you're running it in a bedroom, use sleep mode.
Don't leave it at maximum. Maximum speed is rarely necessary in a domestic setting except during specific pollution events (heavy cooking, window open during high pollen). Running at max permanently increases electricity consumption and shortens filter life.
Don't leave doors open unnecessarily. The purifier is sized for one room. Running it with the door open to a much larger space means it's always working against a much larger volume of air. Close the door to the room being treated.
See our full air purifier roundup for product recommendations, or our guide on how often to change an air purifier filter for the other side of the running cost equation.