Methodology

What we do

We compile published manufacturer specifications, listing data, manuals and published standards. We normalize them into tables that compare like with like. We compute the things nobody publishes — running costs, chiller sizing, heat loads — from first principles, with the working shown so you can redo it with your own numbers. And we date every figure and every source.

That is the whole method. It is unglamorous and it is checkable, which is the point.

What we do not do

• We do not test hardware. No test bench, no lab, no owned units. Where a page says something about how a product performs, it is reading a specification, not a measurement we took.
• We do not accept free products. Not review samples, not loans, not anything.
• We do not accept payment for placement or ranking. No sponsored posts, no paid inclusion.
• We do not hold credentials. Sawyer V. is an enthusiast — not an engineer, not a clinician, not an electrician. Nothing on this site is medical or electrical advice.
• We do not fabricate figures. Where a spec is not published, the cell says “Not published” rather than carrying an estimate.

How picks are made

The criteria differ by category, and in every case we weight what a manufacturer actually publishes heavily. That is not a proxy for quality — it is a statement about what can be verified, and a manufacturer that publishes a checkable figure has given us something to rank on while one that says “powerful” has not.

Saunas

• Heater output against rated room volume, where a manufacturer publishes one
• Circuit requirement — voltage and amperage
• Spectrum, for infrared: far infrared or full spectrum, stated plainly
• EMF as published, and critically the distance it was measured at
• Wood species and grade, particularly outdoors
• Roof covering, on outdoor structures
• Interior dimensions rather than exterior, where available

Cold plunge

• Cooling capacity in HP and, where published, BTU
• Minimum temperature
• Pull-down time with a stated starting temperature — almost nobody publishes this
• Tub volume in gallons, and published external dimensions
• Insulation and whether a fitted lid is included
• Whether pump and filtration are integrated or external

Red light

• Wavelengths in nanometres
• Dual chip or single chip
• Board dimensions
• Flicker specification, as a driver-quality signal
• Irradiance at a stated distance — the spec that would actually determine dose, and which no panel in our survey publishes

The limits of spec-led ranking

This is the section no competitor writes, and it is the most important one here. Ranking on published specifications has real weaknesses and you should know them before you weight anything we say.

1. 1Published specs are marketing documents. A manufacturer chooses which figures to publish, and the omitted ones are usually the unflattering ones. Absence of a spec is informative, but it is not the same as a bad spec.
2. 2Figures are frequently not comparable. EMF without a measurement distance, irradiance without a distance, insulation described as “insulated” — these look like specifications and cannot be ranked against each other.
3. 3Advertised power is often not consumed power. LED ratings and element ratings are not measured wall draw, which makes cost arithmetic an upper bound rather than a figure.
4. 4We cannot assess build quality. Whether joinery holds up, whether a controller lasts six years, whether a compressor is quiet — none of that is in a spec sheet and we do not pretend otherwise.
5. 5We cannot assess experience. How a sauna feels, whether a bench is comfortable, whether a tub is unnerving to sit in. Those matter and we have no access to them.
6. 6Availability moves. A listing verified live one week can be unavailable the next. We date every check and say so where we found one unavailable.

What spec-led ranking is genuinely good at: telling you which products publish enough to be assessed, what the published numbers imply about sizing and cost, and where the whole category is quietly silent. Those are real and they are not available anywhere else in this niche.

How product links are sourced

Every product on this site was found in Amazon's own indexed listings, and every ASIN we use to build a direct product link was confirmed against a live product page during the build. Where that confirmation failed — Amazon serves bot-check pages to automated requests a good deal of the time — the product links to a tagged Amazon search instead of a direct page.

That is deliberate: a search always resolves to whatever stock is actually live, whereas an unverified direct link risks sending you to a dead page. We never write an ASIN from memory and we never invent one.

Prices

We do not run a live price feed, so we do not print prices anywhere on this site. A price typed once would be stale within days and shown to you as though it were current, which is worse than no price at all. Every buy button goes to the live listing, where the number is the retailer's and it is right.

Health claims

Every physiological claim on this site links to a specific, named source, and where evidence is observational rather than causal we say so in the sentence rather than in a footnote. Where evidence is thin or contested, we say that too. We do not use the words “detoxifies” or “cures”, we do not publish calorie-burn figures, and we do not claim any product treats any condition. There are 173 citations across the site.

We also publish findings that work against the products we link — the research on cold immersion blunting resistance-training adaptations is on our cold plunge evidence page, prominently, because a site that only cites research supporting what it links to is not reporting research.

Corrections

If we get something wrong, we fix it, date the change and describe it. If you have found an error — a spec we misread, a figure that has changed, a source that does not say what we say it says — tell us. Corrections get read first. The full policy is in our editorial policy.

Money

This site earns affiliate commission when you buy through a link. Commission never affects a ranking or a verdict, and a meaningful number of our pages carry no buy links at all — every health-evidence page, every protocol page, and every page where attaching a product would have been tenuous. Where a page earns nothing, it says so on the page. The full statement is in the affiliate disclosure.

Review cadence

Roundups are re-verified against live manufacturer specs quarterly, and product links are re-checked on the same schedule. Pages are only re-dated when their content actually changes — we do not restamp unchanged pages, because a sitemap claiming everything changed every day is a sitemap Google stops believing.