How we get our numbers
Prices
We read the price published on the manufacturer's own product page, automatically, once a day. We store every reading. The "90-day low" and "typical price" figures on our pages are computed from that stored history — not estimated, not supplied by anyone. Where a price is a limited-time promotion, our history shows it as one.
Specifications
Taken from the manufacturer's published data for that model. For air purifiers that means the AHAM-verified clean-air delivery rates (smoke, dust, pollen) where the maker publishes them, and the maker's own figure, labelled as such, where it does not. For air conditioners it is the DOE seasonally adjusted cooling capacity, not the older ASHRAE number, unless we say otherwise. For dehumidifiers it is the DOE pints-per-day rating. Where two sources on a manufacturer's own site disagree, we say so on the page rather than silently picking one.
Coverage and running-cost figures
Any room-coverage or cost-to-run number is one of two things, and we always label which:
- the manufacturer's stated figure, or
- a calculation from a rated capacity and a stated assumption (ceiling height, air changes per hour, electricity price), with the assumption shown.
These are estimates. Real rooms leak, filters load up, and compressors cycle; expect less than the label.
What we never do
- We do not accept payment for a recommendation, a ranking or a placement.
- We do not publish manufacturer-supplied copy as our own.
- We do not invent test results.
- We do not make health claims. Where an authority's advice is quoted, it is quoted and attributed.
Corrections
If a number here is wrong, tell us and we'll fix it and note the change on the page. Every page carries a "last updated" date and a change log.