How our welder comparisons are researched
Where specifications come from
We display maximum output only with an explicit ampere unit, duty cycle only with an explicit percentage and, where stated, its amperage basis, steel thickness only with an explicit inch value, and dual-voltage, AC TIG or plasma wording only when the listing states it. A seller amperage is not a measured output; a duty cycle without its amperage basis is incomplete. These attributes determine buyer-intent eligibility and are shown as evidence; they never add invented performance bonuses. The numeric evidence component uses the documentation completeness formula below consistently across the catalog.
Each extracted attribute retains its source phrase. Unknown values remain unknown; a model number such as 200 in a product name is not an amperage. A duty cycle without its amperage basis is displayed as incomplete. We do not derive weldable thickness from amperage.
Documentation component
Documentation completeness = 100 × [0.5 × min(feature bullets / 8, 1) + 0.3 × min(listing images / 5, 1) + 0.2 × (brand stated ? 1 : 0)], rounded to a whole number. These exact-ASIN stored listing inputs describe how much documentation a seller provides, not measured arc performance, duty cycle or weld quality.
The same documentation component applies to all eligible machines. Plasma and AC TIG wording determine membership in their respective shortlists, not a performance bonus.
Review evidence and eligibility
Where Amazon publicly displays customer reviews for a listing (average star rating and review count captured from the public product page), the raw editorial score is 100 × [0.45 × (Amazon average / 5) × min(review count / 50, 1) + 0.35 × min(log10(1 + review count) / log10(1 + 5000), 1) + 0.20 × documentation score / 100]. The confidence factor min(review count / 50, 1) damps averages based on very few reviews, and the logarithmic volume term rewards large public review volumes, so widely and highly reviewed listings rank ahead of thinly reviewed ones. Listings with no captured public review data use the documentation score alone. This combined index reflects the public Amazon reputation and the listing documentation — it is not a physical test and not our own product testing.
Ranked comparators require complete machines with an exact-ASIN captured average and positive review count. Accessories, consumables, named bundles and dedicated single-process machines are excluded from the multiprocess ranking. The plasma combo list requires an explicit cutting mode; the AC/DC TIG list requires explicit AC output wording. Amazon may share reviews across variants: an exact-ASIN page count does not prove every review concerns only that configuration. Missing review evidence is not a zero-customer claim.
Displayed rating and order
The displayed editorial rating is the raw blended score divided by 10, shown to one decimal on a 0-10 scale. There is no catalog normalization, rank interpolation, forced winner, forced floor or artificial gap. Equal scores remain equal: the available data does not justify a distinction. Ranking uses the unmodified raw score descending, then listing slug for exact ties; slug is a stable identifier, not a quality signal. The same raw score always has the same display rating in every shortlist. This is not a physical test result or an Amazon customer rating.
Known variants share a model-family identifier and appear at most once per shortlist. The score is not a claim of best value, safety, measured arc performance or long-term reliability.
Duty cycle planner
Duty cycle is conventionally rated over a 10-minute period at a stated output current. Arc minutes per period equal duty cycle ÷ 100 × 10; rest minutes equal 10 minus arc minutes; arc minutes per hour equal duty cycle ÷ 100 × 60. A 60% rating gives 6 arc minutes per 10 minutes; a 20% rating gives 2. The planner only reports whether a planned amperage is at or below the stated rating basis; it does not estimate a duty cycle at another amperage, because that comes from the manufacturer's chart. It uses no temperature correction or performance assumption and establishes nothing about thermal protection or safe operation.
Freshness and illustrations
Offer and merchant-photo records are hidden when expired, with a maximum 24-hour lifetime from capture. We do not renew timestamps without a fresh authorized retrieval. Public review observations retain their original dates. Editorial illustrations are labeled and are not product photography or proof of testing.
Consult the exact manufacturer manual for input power, shielding gas, consumables and protective equipment. Never use a generated scene as a safety reference. Read the buying guide or use the duty cycle planner.