Methodology
Every number on this site is either sourced (a certified spec we pulled from a public registry, cited to it) or computed (a figure we derived with a formula we publish below). We never blur the two, and we never invent a spec — a missing value is shown as "not published," not estimated.
How we source performance specs
Efficiency ratings (SEER2, EER2, HSPF2, AFUE) and capacity figures (cooling at 95°F; heating at 47/17/5°F) come from two public sources, joined on the AHRI reference number:
- AHRI Directory — the industry certification database. AHRI's data carries redistribution terms, so we publish our computed layer and cite the AHRI reference number for each unit rather than republishing their table verbatim.
- ENERGY STAR certification data — supplies the ENERGY STAR, Most Efficient, and Cold Climate designations, and carries the AHRI reference number that lets us join the two.
Where a registry doesn't disclose a field, that field renders as "not published." We don't interpolate.
The cold-climate truth: COP and capacity at 5°F
A heat pump's marketing will say it "works down to −15°F." What actually matters is two certified numbers at 5°F: the COP (how much heat it moves per unit of electricity) and the heating capacity (how many BTU/h it can still deliver when it's frigid). We surface both on every heat-pump page and rank our cold-climate guide on them.
How we compute operating cost ($/MMBtu)
Our headline metric is the cost to deliver one million BTU (one MMBtu) of heat. It's the "cost per calorie" of home heating, and it's what makes an efficient heat pump the cheapest box in the house to run.
Gas furnace: $/MMBtu = 10 × gas $/therm ÷ AFUE
Electric resistance: $/MMBtu = (1,000,000 ÷ 3,412) × electricity $/kWh
Constants: 1 kWh = 3,412 BTU; 1 therm = 100,000 BTU. Default prices are EIA U.S. averages (EIA US avg 2026: $0.1883/kWh, $1.68/therm) — the operating-cost calculator lets you enter your own. At U.S. averages, an efficient heat pump delivers heat for about $10.76/MMBtu versus $55.19/MMBtu for electric resistance.
Savings vs. electric resistance is simply (1 − heat-pump $/MMBtu ÷ resistance $/MMBtu) × 100. These are steady-state estimates; real bills vary with weather, defrost cycles, and backup-heat use.
How we source rebates
Incentive data is derived from DSIRE (Database of State Incentives for Renewables & Efficiency). Note the federal 25C tax credit expired 12/31/2025 — the live layer is state, utility, and HEEHRA programs. Rebate rules change constantly, so every rebate page carries a review date.
What we don't do
- No star ratings. We don't run a proprietary score that collapses efficiency, capacity, and price into one undisclosed number. We show the sourced numbers and let you sort by what matters to you.
- No pay-for-placement. Rankings are strictly by a stated, verifiable metric, computed identically for every unit.
- No invented specs. If a registry doesn't publish a value, we mark it "not published" rather than estimate it.
Freshness
Stale data is the incumbent failure mode. Our corpus is re-pulled from AHRI, ENERGY STAR, and DOE CCMS on a biweekly cadence, and every page shows when it was last updated.
Affiliate disclosure
See the full affiliate disclosure. In short: no affiliate or lead-gen links are live yet, and when they go live they will never influence which equipment appears or how it's ranked.
Corrections
Found a wrong spec, a stale figure, or a mismatched AHRI reference? Email erinrose451@gmail.com with the model number and what's wrong. We fix verified errors and update the "last updated" date on the affected page.