Best Air Purifier Under £100 UK (2026): Honest Maths on the True Year-1 Cost

The headline truth before you read further:

The £100 price point is a unit-price illusion — no air purifier in this dataset runs for under £100 in year 1 once filters and electricity are included. Every qualifying model crosses £100 in year 1. The table below shows the numbers from running-cost.json so you can see exactly where the cost goes.

• Coverage above 13 m² at 3 ACH. None of the four models reach it. The Philips 600 is the widest at 13 m². For a UK living room (typically 16–25 m²), none of these are correctly sized.
• An independently certified filter. None of the four models hold Allergy UK certification, ECARF Quality Seal, or EN 1822 classification. The Levoit models carry manufacturer-claimed H13 grades (AHAM-tested at 0.3 µm, not EN 1822); Blueair uses HEPASilent (proprietary); Philips 600 states HEPA without a grade. None of these are equivalent to independent third-party certification.
• A washable pre-filter. None of the four models in this group include a washable pre-filter stage. A washable pre-filter catches larger particles before the HEPA and extends filter life — its absence means the HEPA is doing all the work, which shortens replacement intervals.
• Meaningful published carbon depth. Carbon weight is not published for any model in this group. "Activated carbon" on a product description can mean a thin activated carbon-impregnated mesh or a multi-gram carbon bed — the difference matters for VOC and odour control. None of these manufacturers publish carbon weight for their under-£100 products.

The lowest year-1 cost in this group at £106.41 and the lowest 3-year TCO at £179.25. Room coverage is limited to 8 m² at 3 ACH — suitable for a small single bedroom or box room. The 200S has no air quality sensor, which is a meaningful trade-off versus the 300S. If your room is under 8 m² and you do not need a sensor, this is the most cost-effective pick in the dataset for under-£100 buyers.

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The best under-£100 buy for a 10–12 m² room that needs an air quality sensor. The sensor and auto mode let the machine respond to activity spikes without manual fan adjustment. Year-1 true cost is £133.56; 3-year TCO is £230.70 — the difference in ongoing cost versus the 200S (£51 over 3 years) buys 50% more room coverage and the sensor feature.

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The widest room coverage at 3 ACH in this price group — 13 m² versus the Core 300S at 12 m². HEPA is manufacturer-claimed only (no EN 1822 grade — for that, see the Philips 3200 review). At £145.71 in year 1, it is the second-most expensive in the group despite being priced third. The filter interval is not published; annual filter cost is based on the available replacement filter price.

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The most expensive year-1 cost in the group — for the smallest room coverage

The Blueair Mini Max at £79.00 has the highest year-1 true cost in this group at £144.35 — more than the Core 300S (£133.56) despite covering less room (9 m² vs 12 m²). The reason is the filter: Blueair's replacement filter is priced at £29.99 with a 6-month replacement interval, giving £59.98/year in filter cost. That figure is the highest filter running cost in this group and more than twice the electricity cost of the machine.

The Mini Max also covers the smallest room at 3 ACH: 9 m². The unit price (£79.00) sits between the Core 200S (£69.99) and Core 300S (£84.99), but neither the year-1 cost nor the 3-year TCO (£275.05) is competitive against either Levoit model for the coverage delivered. The Mini Max is listed here for transparency; it is not a recommended pick in this price band.