Methodology
Two things decide whether a recommendation is honest: the data underneath it and what the math does with that data. Both are public here.
1 · The appliance library
130 appliance rows, 130 of them verified against their cited source, drawn from 61 distinct sources:
| Source layer | Rows | What it means |
|---|---|---|
| Manufacturer specifications | 46 | Spec sheets, install manuals, technical data (Goodman, Zoeller, Franklin, Dometic, ResMed, Starlink…) |
| ENERGY STAR certified data | 36 | Aggregated from the official ENERGY STAR product APIs — every stat re-computable from the public dataset |
| U.S. DOE-derived table | 19 | The Virginia Tech Extension reproduction of the DOE appliance table |
| Cross-checked class values | 29 | Device-class values confirmed against ≥2 independent sources; labeled as class estimates, not single-model nameplates |
A row counts as verified only when its value reproduces from the cited source (API re-query, PDF text extraction, or page comparison), with the evidence and date recorded. Aggregates from ENERGY STAR are re-checked automatically every week against the live datasets, so certified values can't silently rot.
2 · The sizing engine
The engine is deterministic and runs the same at build time (static answers) and in your browser (interactive calculator):
- Running watts — sum of every selected device's continuous draw. This sets the minimum inverter rating (plus 10% headroom).
- Startup surge — the single highest inrush moment: motors don't start at running power. We publish per-device surge values — from official Locked-Rotor Amps (LRA) where manufacturers list them (e.g. a ½HP submersible well pump: 32.2A LRA × 230V ≈ 7,400W), from the physics of small compressor motors (conventional fridge compressors start at roughly 9–12× running power), or the generic 3× motor rule where nothing better is published. Inverter-driven compressors are the exception — they ramp and have no locked-rotor spike, and we say so.
- Daily energy (Wh) — each device's watts × its duty cycle (DOE / ENERGY STAR usage hours), summed.
- Recommended capacity — daily Wh × 1.25, covering inverter conversion losses and usable depth of discharge. Your selection of backup duration (4/12/24/72h) scales this.
3 · Product matching and what we disclose
- A station must satisfy three hard constraints: continuous output ≥ your load, surge rating ≥ your peak (unknown surge ratings fail motor loads rather than pass), and capacity ≥ the target (relaxed to 75% when the database has no full match — always labeled with the coverage %).
- Ranking prefers the tightest capacity fit (less paid-for-unused), tie-broken by price; missing prices never outrank real ones artificially.
- Duplicate and spec-clone units don't stack the list; expandable systems are matched against your actual need and labeled with their expansion ceiling.
- When nothing fits — very high-surge loads like whole-house AC — we show an honest empty state instead of a marginal recommendation.
4 · Corrections
Found a number you can source better? Send it in — corrections with a primary source get applied and credited to the source, and the changed row keeps the evidence trail in our review log.