Scope: heated pads, mats, and beds that add or trap warmth for companion pets (dogs, cats, small pets) — electric plug-in, passive self-warming, and microwavable types. Excludes unheated pet beds (Pet Beds & Bedding), reptile/exotic under-tank heaters and heat lamps (Habitat Heating & Lighting), and farm/livestock heated mats (outside the pets vertical even though K&H sells both under one brand).

Seed
1. harvest_date equivalent: the thermostat setpoint and "can the pet get off it" design — never a structured listing field, only in brand FAQ/warning copy, and it is the biggest safety differentiator in the category.
2. Watchmaker persona: notices wattage scales almost linearly with pad area (20W/252sqin, 40W/456sqin, 60W/900sqin) to hit the same ~102°F setpoint — engineered to constant power density, not just "bigger heater for bigger bed."

Sources
[khpet_lectrosoft] https://www.khpet.com/products/lectro-soft-outdoor-heated-bed — outdoor wattage tiers by size, steel-wrapped cord, MET Labs/electrical safety, 102°F thermostat setpoint FAQ — fetched excerpt: "Small 20 watt measures 14x18, Medium 40 watt 19x24, Large 60 watt 25x36... 5½ foot steel wrapped cord... tested & certified by MET Labs... thermostatically controlled to heat to 102°F, regardless of the size."
[khpet_thermopillow] https://www.khpet.com/products/k-h-thermo-pet-pillow-indoor-heated-cat-lap-bed — pet-activated thermostat behavior, UL-beyond safety claim, 10ft cord — fetched excerpt: "A smart, pet-activated thermostat automatically warms the bed only when your pet is inside... safety listed... beyond UL requirements... 120V... generous 10-foot cord."
[khpet_thermokittypad] https://www.khpet.com/products/amazin-thermo-kitty-pad — 4-watt indoor pad wattage floor, size, vet-consult warning — fetched excerpt: "Heated cat bed includes a 4-watt small Pet Bed Warmer... measures 15 x 20... Consult your veterinarian before use with... any animal that cannot voluntarily remove themselves from the heated pad."
[khpet_microwavewarmer] https://www.khpet.com/products/microwavable-pet-bed-warmer — microwavable insert, indoor/outdoor use, same vet-consult warning (independent listing corroborating it) — fetched excerpt: "Indoors or outdoors, place in any pet bed... Do not place pad in confined area where the pet does not have the ability to remove themselves."
[khpet_selfwarmpad] https://www.khpet.com/products/self-warming-pet-pad — no-electricity mechanism, size, washability — fetched excerpt: "Heated cat bed safely and naturally keeps your pet warm using their own body temperature... without electricity... measures 21 x 17... Wash the entire bed on the gentle cycle."
[snugglesafe] https://www.snugglesafe.co.uk/shop/snugglesafe-pet-heatpads/ — microwavable gel disc mechanism, size, heat duration, reheat rule — fetched excerpt: "Heated in minutes...lasts for up to 10 hours... 210mm diameter x 28mm thickness... ONLY re-heat our heatpad once it has completely cooled."
[ul499] https://www.shopulstandards.com/ProductDetail.aspx?productId=UL499 — governing electrical safety standard explicitly includes heated pet mats — fetched excerpt (via tool summary of standard scope): "Heated floor mats/pads without a metallic or thermoplastics enclosure... are excluded... except for heated pet mats" (i.e. heated pet mats are in scope of UL 499).
[neighborhoodcats] https://www.neighborhoodcats.org/winter-shelter — mylar/reflective vs straw insulation distinction; self-warming "Purr Pad" and microwavable SnuggleSafe named as the passive-heat exception for outdoor shelters — fetched excerpt: "Mylar is a thin polyester material that traps and reflects body heat back at its source... An exception to this rule is a Purr Pad which is designed to absorb and retain body heat."
[wikipedia_heatingpad] https://en.wikipedia.org/wiki/Heating_pad — generic primer on electric vs microwavable heating pad mechanisms, pet-trade heat mats — fetched via tool summary, used only for general mechanism language, no disputed numbers drawn from it.

Branches
- heating_mechanism=electric_plug_in → ask wattage, thermostat_control, cord_type, voltage_region; self-warming/microwavable fill and reflective-core facets become irrelevant — supported by the electric-only presence of wattage/cord/voltage across khpet_lectrosoft, khpet_thermopillow, khpet_thermokittypad vs. their total absence from khpet_selfwarmpad and snugglesafe.
- heating_mechanism=self_warming_passive → ask reflective_core_material only; wattage/cord/thermostat/voltage/fill/reheat all irrelevant — supported by khpet_selfwarmpad's "without electricity" claim and neighborhoodcats' mylar explanation.
- heating_mechanism=microwavable_gel → ask fill_material, reheat_behavior; electric-only facets irrelevant — supported by snugglesafe's gel-disc, no-cord, reheat-after-cooling description.
- placement_setting=outdoor_or_unheated_space or both → ask weatherproof_rating — supported by khpet_lectrosoft being the only one of the three K&H products marketed "indoor OR outdoor," carrying a waterproof claim the indoor-only lap bed and pad do not.

Noise (spec-sheet rows seen but not made facets)
- Price, color/fabric pattern options, included free fleece cover, warranty length, "25+ years of experience" marketing copy — not expertise, generic to any product.
- Farm/livestock heated mats, chicken warmers (K&H sells these under the same brand/collections) — out of scope: not a companion-pet product, belongs outside the pets vertical.
- Straw and raw Mylar blankets used as DIY shelter insulation (neighborhoodcats) — these are insulation materials a caretaker buys separately, not a "pet heating pad" product, so left out as a facet though cited for the reflective-material mechanism.
- Exact cord length in feet varies by product (5.5ft vs 10ft) — folded into cord_type qualitatively rather than a separate low-value numeric facet experts don't actually compare.

Corrections (2026-10-26)
- Added facet `cover_fill_material_quality` (fleece/polyester vs. cotton/low-grade fill), the buyer's-guide fire/safety criterion with no prior facet coverage; evidence k9ofmine (criterion) + khpet_thermokittypad (polyester-cover corroboration); added k9ofmine reference.
- Reworded `power_density_w_per_sqin`'s `why` text and added explicit `evidence: [khpet_lectrosoft]` to flag the 0.067-0.088 band as single-listing-derived, not a verified cross-brand range.
- Left `reheat_behavior`'s single-source "several hours" note unchanged: checker marked this fix optional/minor and the facet is already annotation-only, not a hard filter.