Where our numbers come from
Every estimate on Ballpark Lab is built from primary-source data — not other blogs — and we show exactly where each number comes from. Solar and pool costs are data and engineering topics, not medical, legal, or financial advice, so we publish under organizational authorship rather than a single named expert.
Accountability lives in the method, not a bio: a transparent methodology, the cited sources below, visible “last updated” dates, and a real way to reach us with corrections. Ballpark Lab is maintained by the Ballpark Lab Research Team.
We combine data from multiple official U.S. government data services and primary industry sources — refreshed on a visible cadence — so every estimate is grounded in named, checkable data rather than guesses.
Live data feeds
- U.S. EIA API v2 — State residential electricity and natural-gas prices — 12-month averages, refreshed monthly
- OpenEI Utility Rate Database (URDB) — The actual utility and tariff serving a paid report's address — maintained for the U.S. Department of Energy
- Google Solar API — Per-roof geometry, production, and sun-exposure imagery in the paid roof analysis
- NREL PVWatts v8 — Per-state solar production curves and per-roof hourly modeling (NSRDB 2020 TMY weather), refreshed quarterly
- ENERGY STAR certified products — Certified heat-pump and pool-pump models and efficiency data (SEER2/HSPF2/WEF), refreshed from the EPA dataset
Reference sources
- NREL — Peak sun hours by state
- DSIRE + state programs — Curated state incentives and net-metering rules
- IRS / federal policy — 25D and 25C credit status (both $0 — expired 2025-12-31)
- Industry pricing surveys — Installed prices for solar, pool, fence, driveway, siding, and HVAC (Angi/HomeGuide-class surveys + trade benchmarks), refreshed quarterly
Primary sources & what each one feeds
U.S. DOE / EIA
Solar + Pools + HVAC- Residential electricity prices for all 50 states + DC + PR — EIA API v2, electricity/retail-sales (monthly), used as trailing-12-month averages
- Residential natural gas prices by state — EIA API v2, natural-gas/pri/sum (monthly, $/MCF → $/therm at 10.37)
- Refreshed monthly by script; every page shows the 12-month window it averages
NREL (National Renewable Energy Laboratory)
Solar- Average daily peak sun hours by state
DSIRE (Database of State Incentives for Renewables & Efficiency)
Solar- State-level solar incentives as a fraction of system cost
- Net-metering treatment — how each state credits exported energy
OpenEI Utility Rate Database (URDB)
Solar- The actual utility serving a purchased report's address — utility name, blended residential ¢/kWh, time-of-use peak/off-peak spread, fixed monthly charge
- Fetched once per paid roof report and saved with it (maintained for the U.S. DOE)
Google Solar API
Solar- Per-roof geometry, usable panel count, and production for the paid roof analysis (buildingInsights)
- The sun-exposure heatmap in the paid report — annual solar flux + roof mask rasters (Data Layers), rendered once per purchase
NREL PVWatts v8
Solar- Per-state monthly production curves in the free solar calculators (NSRDB 2020 TMY, 1 kW reference array)
- Hourly production modeling and the NREL cross-check in the paid roof report
IRS guidance & federal policy (OBBBA)
Solar- Residential federal credit (Section 25D) status — expired 2025-12-31, now $0
- Commercial credit (Section 48/48E) claimed by lease/PPA system owners
- Residential HVAC credit (Section 25C) status — also expired 2025-12-31 under the same law
Pool & Hot Tub Alliance and industry pricing surveys
Pools- Pool shell, sitework, and feature cost ranges by type (gunite, fiberglass, vinyl)
- Construction and safety standards that shape real-world bids
HVAC install pricing surveys (Angi, HomeGuide)
HVAC- Installed per-ton AC/heat pump rates, furnace and mini-split pricing bands (2026)
- Ductwork repair/replacement and electrical-upgrade allowances
IRS §25C guidance & ACCA Manual J
HVAC- 25C Energy Efficient Home Improvement Credit status — expired 2025-12-31 under OBBBA
- Load-calculation methodology our screening estimate approximates (and defers to)
ENERGY STAR certified products (EPA, data.energystar.gov)
HVAC + Pools- Real certified heat-pump models and efficiency percentiles in the HVAC calculator and the certified-heat-pumps report
- Variable-speed pool pump picker (WEF ratings) in the pool maintenance calculator
Fence install pricing surveys (Angi, HomeGuide)
Fence- Installed wood/vinyl/chain-link pricing — industry installed-price surveys
- Regional frost-line data driving post-depth assumptions
Driveway install pricing surveys (Angi, HomeGuide)
Driveway- Asphalt/concrete/paver installed pricing — industry surveys
- Demolition and curb-cut references
Siding install pricing surveys (Angi, HomeGuide)
Siding- Vinyl/fiber-cement/engineered-wood installed pricing — industry surveys
- Siding-square methodology
See the data in action
These sources feed live tools and an open dataset. Every result shows its assumptions, and the methodology spells out each formula in plain English.
Solar data updated June 30, 2026· Pool data updated June 30, 2026 · Fence data updated July 1, 2026 · Driveway data updated July 6, 2026 · Siding data updated July 6, 2026 · HVAC data updated July 10, 2026