Solar Quote Verifier

Overview

Solar proposals are engineered optimism: production modeled at perfect orientation, payback quoted before inverter replacement, financing that hides a 7% dealer fee, "free panels" leases with escalators that outpace utility rates. scripts/solar_quote_check.py re-computes the quote's economics from first principles — regional insolation, orientation derates, panel degradation, inverter replacement at year 12–15, utility rate escalation, ITC 30% credit — and flags the sales-tactics layer (overstated production, $/W above market, roof older than the loan, lease escalators).

When to Use

• An installer sends a proposal (email PDF numbers → this skill).
• A door-to-door / cold-call solar pitch with "eliminate your bill".
• Comparing 2–3 competing quotes and needing a like-for-like scorecard.
• Reviewing a lease/PPA offer against buying.

Don't use for: off-grid system design (battery sizing is a different instrument), commercial/C&I scale (>100 kW), or countries with wildly different subsidy regimes — the tool's tables are US-centric; regional insolation can be overridden.

How It Works

1. $/W sanity: installed cost ÷ DC wattage vs 2026-ish residential band ($2.50–3.50/W pre-ITC; >$4/W = overpriced; >$5/W = walk away).
2. Production check: quoted kWh ÷ (kW × 365) vs regional sun-hours × 0.84 system derate. Overstatement >10% = RED FLAG (the #1 proposal lie).
3. Payback, honestly: annual value of production at your rate, escalated 2.5%/yr, minus 0.5%/yr degradation, minus one inverter replacement (year 12–15, ~$0.35/W), ÷ net cost after ITC. Compare to quoted payback.
4. Financing X-ray: dealer-fee loans (APR vs "low payment"), lease/PPA escalator (2.9%/yr typical) vs utility escalation (2.5%) — if the escalator runs hotter, year-15 lease payments exceed grid parity.
5. Conflict checks: roof age (asphalt shingle >10 yr old + 25-yr panels = reroof-first math), ITC eligibility (you must have tax appetite; lease/PPA gives the credit to the company), net-metering changes.
6. Verdict: FAIR / OVERPRICED / RED-FLAG with the three biggest levers.

Using the Script

# Demo: a typical overstated proposal
python3 scripts/solar_quote_check.py --demo

# Check a real quote (all costs pre-incentive, USD)
python3 scripts/solar_quote_check.py \
  --kw 8.4 --cost 32760 --quoted-kwh 13500 \
  --rate 0.17 --region southwest --orientation s --pitch 30

# Loan scenario
python3 scripts/solar_quote_check.py --kw 8.4 --cost 32760 \
  --quoted-kwh 13500 --rate 0.17 --region southwest \
  --loan-apr 6.9 --loan-years 20

# Lease/PPA sanity
python3 scripts/solar_quote_check.py --kw 8.4 --ppa-rate 0.13 \
  --ppa-escalator 2.9 --rate 0.17 --region southwest

Worked Example

8.4 kW at $32,760 ($3.90/W — overpriced band) quoting 13,500 kWh/yr in the southwest: realistic production ≈ 8.4 × 6.0 sun-h × 365 × 0.84 ≈ 15,460 kWh (quoting LOW here — rare), but at $3.90/W the honest payback is ~13 yr cash vs the quoted 9 yr once the year-13 inverter ($2,940) and 2.5%/yr rate escalation are modeled. Verdict: OVERPRICED — negotiate to $3.20/W or get competing bids; the system itself pencils out.

Common Pitfalls

1. Believing quoted production. It's modeled at ideal azimuth/tilt with clean panels and no shade. Recompute from regional sun-hours × 0.84.
2. Payback without the inverter. String inverters die at 12–15 yr inside a 25-yr finance term; microinverters have better warranties but cost more per W up front.
3. The dealer-fee loan. "2.99% financing!" usually adds 10–15% to the price. Compare CASH price vs LOAN price on the same system.
4. Lease/PPA escalator ≥ utility escalation. 2.9%/yr escalator on a 2.5%/yr utility glide path means the "savings" shrink every year and can go negative — the classic PPA trap.
5. ITC you can't use. The 30% federal credit needs tax liability; if you can't absorb it, your net cost is a third higher (or the credit belongs to the lease company — that's why their pitch "includes" it).
6. Old roof, new panels. Removing/reinstalling panels to reroof costs $2,000–6,000. Panels outliving a 12-yr-old shingle roof is a real conflict.

Verification Checklist

• $/W computed and banded (fair/overpriced/walk-away).
• Production estimate independently recomputed, not trusted.
• Payback includes degradation + inverter replacement + escalation.
• Loan and PPA modes disclose their respective traps.
• Roof-age and ITC-eligibility conflict checks surfaced.
• Verdict names the three biggest levers, not just a number.