Model & assumption history
Major changes are recorded here so a calculator result can be understood in the context of the model version that produced it.
v6.1.5 · October 1, 2026
Stabilized shared calculator UI behavior; standardized real guide/calculator photo pairs; improved essential-input prioritization, inline validation, source/default explanations, worked examples, decision clusters, discovery filters, responsive images, and release checks.
v6.1 · October 1, 2026
Standardized calculator UX, source/default labeling, scenario presentation, trust content, imagery, analytics event hooks, and UI contract checks. No hidden third-party tracking was added.
v6.0 · October 1, 2026
Added the shared calculator core, Water Heater Repair vs. Replace, consistent limitations, editable default labels, and expanded regression coverage.
v5.5 · October 1, 2026
Separated core decision math from browser UI, added “See the math,” scenario checks, explicit horizons, and neutral lower-modeled-cost wording.
Website v6.2.2 — October 3, 2026
Required-field validation, invalid-result clearing, accessible error descriptions, print/save comparisons, privacy information and model scope documentation improved. Calculator equations and example defaults remain Model v6.1.5. This website release is not a new source review or a change to economic assumptions.