About Solar Ledger

Why this site exists and what we will and won't do.

We don't sell installs. We don't sell leads.

Most online solar calculators are built by, or affiliated with, installers. Their incentive is to make the system look as attractive as possible so you fill out the form. Ours isn't. We show payback the way the math actually works, including the parts that are inconvenient for sellers.

Concrete example: as of 2026-01-01, the federal Residential Clean Energy Credit (§25D) was repealed by the One Big Beautiful Bill Act (P.L. 119-21). Systems installed in 2026 do not get the 30% credit anymore. Many seller-affiliated calculators still show that 30%. Ours doesn't.

What we do

Pull live production estimates from NLR PVWatts V8 (the same model the Department of Energy uses for federal estimates).
Apply current federal policy as of the most recently verified date.
Use utility-specific export tariffs with explicit validity windows.
Stamp every regulated or tariff number with a verification date and source.

What we don't do

Sell, broker, or refer solar installations.
Collect emails behind a results gate.
Show numbers without a verification date.
Round optimistically. Payback in years is rounded to one decimal.

Methodology, briefly

Production: NLR PVWatts V8 with the user's latitude / longitude (mapped from ZIP), 14% default system losses, south-facing 20° tilt, fixed roof mount, standard module type.
Federal incentives: pulled from lib/config/federal.ts; current value is 0% (§25D repealed for post-2025 installs).
State incentives: pulled from lib/config/states/<code>.ts; Arizona's credit is 25% of system cost, capped at $1,000 (A.R.S. §43-1083).
Utility rates: state-level retail estimate from EIA + utility-specific export tariffs. Arizona uses net billing (not net metering), so self-consumption is valued at retail and exports at the utility's tranche rate.
Lifetime: 25-year horizon, 3%/yr rate escalation, 0.5%/yr panel degradation.

Disclaimers

This site provides estimates for informational use only. It is not a binding quote, not financial advice, and not tax advice. Tax credits depend on your specific tax situation; consult a qualified professional.