Our method

Everything we show must be checkable: which source, which price, when we saw it.

1. The ranking: a consensus of tests

We take the current lists of five to eight reputable testers, such as Vacuum Wars, RTINGS, Wirecutter and TechRadar. From every source we note the position of each product and the use it is recommended for, for example "best for pet hair" or "best budget pick".

Our ranking is a consensus of those positions and mentions (a Borda-style point count), never an average of their grades: an 8 from one tester means something different from an 8 from another. A recommendation for a specific use ("best budget model", "best for pets") counts too, at seventy percent of a general recommendation. Only models sold by US stores count. Every source is named with a link and the date we checked the list. We copy no text.

2. Prices: fetched and checked daily

Every day we fetch the price, the seller and the delivery time at every store we follow, from the store's own product data, and for Amazon.com from Keepa's price tracking. Every price shows when we last saw it.

A price that deviates strongly from what we saw last week is marked suspect and not shown until confirmed. A silent read error is how comparison sites lose their credibility. We keep every observation, so the price history and the 90-day low come from our own data.

3. The real price: shipped, and compared like for like

• Shipping to the United States counts, at every store.
• Prices are shelf prices, before sales tax. Sales tax depends on your state and the store adds it at checkout, so no single figure would be right for every reader.
• Sales by the store itself and sales by a marketplace seller are kept apart.
• Refurbished and used offers are shown as a separate category, never mixed with new.
• Delivery time is part of the deal: tomorrow or in five days makes a difference.

4. Fake discounts

US federal rules set no fixed period for a "was" price. The FTC's guides only ask that it be a price the item was really offered at, openly and for a reasonably substantial time. We hold every store to the European rule instead: a discount is real only when the sale price is below the lowest price that store charged in the 30 days before the sale. Because we keep the list price next to every observed price, we can check and show this: claimed "was $1,299". The lowest price we saw in the last 30 days was $1,099. Amazon's crossed-out "List Price" is the maker's recommended price, and we label it as such rather than judge it.

5. Buy now or wait

On every product page: today's price against the range of the last 90 days, how often and how deep this product drops in price, and how long ago the last drop was. Sometimes the honest answer is "wait". That costs us a commission today and earns a reader who comes back.

6. How we make money

Best at Best is free. Some links to stores are affiliate links: buy through one and we may earn a commission from the store or its affiliate network. The price you pay does not change. The commission never influences the ranking, the alternatives or the advice. Those come from the same data for every store. We sell nothing ourselves and there are no paid placements. Every page with links to stores says so next to them.

7. What we do not do

• No paid tests (Consumer Reports) as a source: they are licensed and cannot be checked freely.
• No average of other sites' scores, and no aggregators of aggregators.
• No copied review text. Only positions and labels, with attribution.
• No reselling of products. We are a guide, not a store.