"Cheap" should mean low cost to own, not just low sticker price. Plenty of £50 purifiers are false economy: tiny CADR, and proprietary filters that cost more than the machine within two years. The genuinely cheap route is high airflow through standard MERV-13 media.
Ready to clean up your London air?
Luggable MERV-13 kits deliver up to 681 m³/h CADR — built on the Corsi-Rosenthal principle, from £229. Ships from Oxford in 2–3 days.
Shop the UK store → See all kitsThe two truly cheap options
- Build a Corsi-Rosenthal box — £60–£120, unbeatable airflow per pound, a bit bulky and loud. Build guide →
- Buy a MERV-13 kit — from £229, quieter and tidier, filters from ~£58 a pair, no lock-in.
Running cost
The fans draw about 15W, so electricity is roughly £2 a year even running most of the day. Filters are the main ongoing cost, and standard MERV-13 media keeps that low. That's what ‘cheap’ should actually mean.
Frequently asked questions
What's the cheapest air purifier that actually works?
A DIY Corsi-Rosenthal box (£60–£120) offers the most clean air per pound. A MERV-13 kit from £229 is the cheapest quiet, tidy option once you count filter costs.
Why avoid £30–£50 mini purifiers?
Most have tiny CADR and rely on proprietary filters that quickly cost more than the unit. They can't clear a real room of PM2.5.