Every product on this site runs through the same four steps. This page explains them so you can judge how much weight to give a score.
1. Verify
We check every figure against a named source: manufacturer documentation, a third-party certification listing, or a retailer specification. The source appears in the table next to the number. Where a manufacturer will not publish a figure, we print “not published” rather than estimate, and we treat the omission as information.
2. Model the cost of ownership
Five years of ownership, itemised:
- Purchase at the street price on the date of publication.
- Installation at typical professional rates, where the product needs it.
- Electricity from the manufacturer’s stated power draw and a stated assumption about hours of use, priced at the US residential average per kWh.
- Consumables from the published replacement schedule at current prices.
The arithmetic is shown on the page so you can substitute your own electricity rate or usage pattern.
3. Compare
Each product is scored against the others in its category on five criteria: verified performance, cost to own, materials and build, warranty and support, and manufacturer transparency. The overall figure is an analysis score, not a test result.
4. Disclose the limits
We have not felt the build quality of a sauna or heard how loud a purifier runs on high. Where a claim rests on thin evidence, or where a certification covers less than the marketing implies, we say so in an evidence note next to the claim.
When we update
Pages are re-verified when a product gets a hardware revision, when its price moves more than 15 percent, when the electricity rate assumption changes, or every 12 months, whichever comes first. The date at the top of each page is the last verification.
This is not medical advice
We analyse equipment, not health outcomes. Nothing on this site diagnoses, treats or prevents any condition. Where we cite research, we link the primary source and describe what it does and does not support.