Is it expensive to leave an air purifier on 24/7?

No. A mid-size HEPA unit on a medium setting uses roughly 0.7 kWh a day, which is about 12 cents at the US average rate of 17.5 cents per kWh, or $3.70 a month. Running it continuously is also how the device is designed to be used — air quality benefit depends on sustained air changes per hour, and a purifier switched on for an hour when a room already smells has largely missed the point.

Do filters cost more than the electricity?

Almost always, and usually by a wide margin. A genuine HEPA plus carbon filter set costs $40 to $120 and lasts 6 to 12 months, so filter cost commonly runs $60 to $150 a year against $25 to $60 in electricity for continuous running. When comparing models, the filter replacement price and interval matter more to lifetime cost than the wattage on the box or even the purchase price.

Does the highest fan speed cost much more?

Proportionally yes, though the absolute numbers stay small. A unit drawing 15 watts on low may draw 60 to 80 watts on turbo, so four to five times the energy — but that is still only about 30 cents a day at the US average rate. The practical approach is to run turbo for 20 to 30 minutes to clear an event like cooking smoke or a wildfire smoke intrusion, then drop back to a quiet medium setting for continuous operation.

Are ionizers or UV models cheaper to run?

Slightly on the meter and not worth choosing on that basis. An ionizer adds a few watts and a UV lamp 5 to 20 watts. The larger issue is effectiveness and byproducts: the California Air Resources Board maintains a list of air cleaners certified not to exceed its ozone emission limit, and devices that generate ozone deliberately are not recommended for occupied spaces. Mechanical HEPA filtration remains the approach with the strongest evidence behind it.

How do I find my own unit's consumption?

The nameplate on the back or base lists watts, but usually only the maximum on the highest setting, which most people never use. A plug-in energy monitor costing $20 to $35 gives the real draw at each speed, and many purifiers with app connectivity report it directly. Whatever it says, expect the number to be small — air purifiers are among the lowest-draw appliances that run continuously in a home.

How Much Electricity Does an Air Purifier Use Per Day?

Written & researched by Derek Holt Home & Appliances Editor

Updated October 2026

Over-the-shoulder view of a person adjusting a floor-standing air purifier in a quiet living room, in soft early-morning light

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The short answer: a mid-size HEPA air purifier uses about 0.5 to 1.0 kWh per day running 24 hours on a medium setting — call it 0.7 kWh, or roughly 12 cents a day at a US average residential rate of 17.5 cents per kWh — the EIA publishes the current price for your state. That is $3.70 a month and about $44 a year of continuous operation. Small bedroom units use 0.2 to 0.5 kWh a day; large whole-room units on high can reach 2 kWh. Filters cost more than the electricity in almost every case.

For context, running an air purifier around the clock uses roughly the same electricity as a 30-watt light bulb left on. We do not physically handle the purifiers we rank; our picks come from aggregated owner reviews and expert consensus, described in how we rank, with the ranked field in best air purifiers.

Daily consumption by size and speed

Unit	Low	Medium	High	kWh/day at medium, 24 hr
Desktop / small bedroom (up to 200 sq ft)	4 – 8 W	10 – 18 W	25 – 35 W	0.24 – 0.43
Mid-size room (200 – 400 sq ft)	8 – 15 W	25 – 40 W	50 – 80 W	0.60 – 0.96
Large room (400 – 800 sq ft)	15 – 25 W	40 – 60 W	80 – 120 W	0.96 – 1.44
Whole-floor / open plan	20 – 40 W	60 – 100 W	120 – 200 W	1.44 – 2.40
DIY box fan and filter build	—	50 – 90 W	—	1.20 – 2.16

A note on the last row: a box-fan-and-filter build is a genuinely effective option that research during wildfire seasons has supported, but it is not the low-energy choice — a box fan motor is far less efficient than the purpose-built brushless motors in modern purifiers. See how to build a DIY box fan air purifier for when it makes sense.

Low-angle view of a person adjusting a floor-standing air purifier in a quiet living room, in warm late-afternoon light

Cost by state rate

Figures for a mid-size unit at medium speed, 0.72 kWh per day.

Rate per kWh	Per day	Per month	Per year
11¢ — WA, ID, ND	$0.08	$2.38	$28.90
14¢ — TX, TN, MO	$0.10	$3.02	$36.79
17.5¢ — US average	$0.13	$3.78	$45.99
25¢ — NY, NH, VT	$0.18	$5.40	$65.70
32¢ — CA, MA, CT	$0.23	$6.91	$84.10
44¢ — HI	$0.32	$9.50	$115.63

The formula is watts ÷ 1,000 × hours × rate per kWh. Use the all-in rate from your bill rather than the advertised supply rate. Certification narrows the range: ENERGY STAR room air cleaners are more than 50 percent more energy-efficient than standard models, saving about 211 kWh and $18 to $40 a year.

Three-quarter view of a person adjusting a floor-standing air purifier in a quiet living room, in warm late-afternoon light

Filters are the real running cost

Item	Interval	2026 cost	Annual
True HEPA filter	6 – 12 months	$30 – $90	$30 – $180
Activated carbon filter or sleeve	3 – 6 months	$15 – $45	$30 – $180
Washable pre-filter	Rinse monthly	$0	$0
Combined HEPA plus carbon cartridge	6 – 12 months	$40 – $120	$40 – $240
UV lamp, if fitted	1 – 2 years	$20 – $50	$10 – $50
Electricity, continuous mid-size	—	—	$29 – $84

Filter cost commonly runs two to three times the electricity cost, and it varies far more between models than wattage does. Two purifiers with almost identical performance can differ by $100 a year in filters, which over a five-year life is more than either unit cost to buy. Check the replacement price and stated interval before purchase, and rinse the washable pre-filter monthly — it is the cheapest way to extend HEPA life, because the pre-filter catches the hair and lint that would otherwise clog the expensive element.

Over-the-shoulder view of a person adjusting a floor-standing air purifier in a quiet living room, in warm late-afternoon light

Running it sensibly

Run it continuously on a low or medium setting rather than intermittently on high. Benefit depends on sustained air changes per hour, and continuous quiet operation is both more effective and, on many units, more efficient than repeated turbo bursts.
Match the unit to the room. A purifier rated for 200 sq ft running flat out in a 500 sq ft room uses more energy and delivers less than a correctly sized unit on medium.
Use auto mode if it has a real particle sensor. It drops to low in clean conditions, which is where most of the day is spent.
Place it with clearance — a purifier pushed against a wall or under furniture recirculates its own clean air. See where to put an air purifier.
Turbo has its place: 20 to 30 minutes after cooking, during a wildfire smoke event — the EPA recommends a portable air cleaner to remove fine particles and creating a clean room — or when someone with allergies is about to use the room.

For the filter question in detail see how to replace an air purifier filter and true HEPA vs HEPA-type. On whether the device does what people hope, do air purifiers help with allergies and do air purifiers help with dust are the honest answers, and the ranked field is in best air purifiers. Everything else is at the air quality hub.