Frequently Asked Questions

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Our estimates are based on regional peak sun hours, typical system performance ratios (0.75–0.80), and current average utility rates from EIA data. Estimates are generally accurate within ±10–20% for most U.S. locations. Actual savings depend on your specific roof orientation, shading, local utility rate structure, and the exact system installed. A licensed installer will provide a site-specific assessment using professional software like Aurora or PVWatts.

A peak sun hour is one hour of sunlight at an intensity of 1,000 watts per square meter — the standard test condition for solar panels. It's the key factor determining how much electricity your panels will produce. Phoenix, AZ averages about 6.5 peak sun hours per day; Seattle, WA averages about 3.5. More peak sun hours = more electricity = bigger savings.

Many factors cause variation: your installer uses LiDAR roof modeling, shade analysis, and your exact utility rate schedule (including time-of-use rates, demand charges, and net metering policy). Our calculators use regional averages as approximations. If your installer's production estimate is significantly higher than ours, ask them to walk you through their assumptions — especially shading and performance ratio.

The federal 30% residential solar tax credit (Section 25D) expired December 31, 2025 under the One Big Beautiful Bill Act. Homeowner-owned systems installed in 2026 or later do not qualify for this federal credit — there is no phase-down to 26% or 22%; that Inflation Reduction Act schedule no longer applies. While it was active, the ITC (26 U.S.C. § 25D) let you deduct 30% of the cost of a residential solar installation from your federal income taxes — for a $25,000 system, that was $7,500 off your tax bill. If your system was fully installed on or before December 31, 2025, you may still be able to claim the 30% credit on your 2025 taxes — consult a tax professional. There is no retroactive clawback for anyone who already claimed it. State and utility incentives (see our Tax Credit calculator) are unaffected by this change.

This applies only to systems fully installed on or before December 31, 2025 (see above — the credit has since expired for new installs). The ITC is a non-refundable tax credit — meaning it reduces your tax liability dollar-for-dollar, but you won't receive the balance as a refund if the credit exceeds your tax bill. However, any unused portion rolls forward to future tax years. Consult a tax professional to understand how the credit applies to your specific tax situation.

For systems installed through December 31, 2025 — yes. Under the Inflation Reduction Act, standalone battery storage systems installed after January 1, 2023 were also eligible for the 30% ITC, even if not paired with solar panels (batteries installed before 2023 had to be charged by solar to qualify). This entire ITC pathway ended for systems installed in 2026 or later, since the underlying credit expired December 31, 2025.

These are solar cell technologies with different efficiency and temperature characteristics:

Mono PERC — The current mainstream standard. Passivated Emitter and Rear Cell design captures light from both sides. Efficiency: 19–21%. Best price-per-watt value.

HJT (Heterojunction) — Combines crystalline and thin-film layers for superior low-light performance and very low temperature coefficients. Efficiency: 21–23%. Premium price, excellent for hotter climates.

TOPCon (Tunnel Oxide Passivated Contact) — The newest mainstream technology. Higher efficiency than PERC with competitive pricing as manufacturing scales. Efficiency: 21–23%. Increasingly the new standard.

Solar panels lose efficiency as they heat up. The temperature coefficient (Pmax) tells you how much power a panel loses for every 1°C above 25°C (test conditions). A panel with -0.26%/°C (like SunPower HJT) loses significantly less power on a hot 90°F day than one with -0.35%/°C. In hot climates like Arizona, Texas, or Florida, a lower temperature coefficient can meaningfully increase annual production.

Standard residential panels range from about 18% to 24% efficiency. Anything above 20% is considered high-efficiency. The efficiency rating affects how many panels you need for a given system size — a 22% panel produces more power per square foot than a 19% panel, which matters if roof space is limited. For most homeowners, high efficiency is worth the premium only when roof space is constrained.

We strongly recommend getting at least 3 quotes. Solar installation pricing varies significantly — sometimes by $5,000–$10,000 for the same system. Use our calculators to establish an independent baseline before talking to installers, so you can evaluate each quote against objective benchmarks rather than just comparing installers to each other.

Key factors: NABCEP certification (North American Board of Certified Energy Practitioners), at least 5 years in business, local reviews on Google and BBB, verified manufacturer authorization for the panels they're installing, and a detailed written proposal that specifies panel model, inverter model, system size, projected annual production (kWh), and warranty terms for all components.

Please contact us with the panel name, the spec you believe is incorrect, and the source (manufacturer datasheet URL if available). We take accuracy seriously and will verify and update promptly.