Scenario: a $400/month electric bill. Assumes 3%/yr rate increases, 0.5%/yr panel degradation and no federal tax credit (the 30% §25D credit ended for systems installed after Dec 31, 2025). How we calculate
Data approachEIA rates · NREL sun hours · 2026 federal policy · methodology
A $400/month electric bill in the US typically needs 49 solar panels (19.6 kW) at national average electricity rates and sun hours — about $58,800 installed with 16.3-year payback. The 30% federal Residential Clean Energy Credit (IRC §25D) ended for systems installed after December 31, 2025, so a solar system you buy and install in 2026 gets no federal tax credit. State-by-state, system size ranges from 5.8 kW in Hawaii to 28.8 kW in North Dakota, and payback spans 6.0–26.3 years.
Payback depends on two things more than sunshine: the retail electricity rate and how your utility credits exported power. States with full retail net metering and high rates pay back fastest; states without statewide net metering take much longer unless you size to daytime use or add a battery.
Estimates use EIA state average residential rates, NREL sun hours, a 0.82 derate, $3.00/W installed, no federal credit, and a bill-offset share set by each state’s net-metering category. Methodology.
⚡ System Size
How Bill-Based Sizing Compares to Home Sq Ft Guides
$400/month maps to roughly 4,000 sq ft in national usage intensity — close to our 4,000 sq ft sizing tier.
Direct answers for US homeowners — sized for a $400/month electric bill.
Nationally, a $400/month bill (~2,199 kWh/month) needs about **49 panels** (19.6 kW) at average US rates and sun hours. State totals range from **15** in Hawaii to **72** in North Dakota.
**Hawaii** leads at **6.0-year** payback (5.8 kW, $17,300 installed). **Tennessee** is slowest at **26.3 years**, largely because of its net-metering rules and electricity rate.
The US average is about **$58,800** for a **19.6 kW** system. There is no federal tax credit for homeowner-owned systems installed in 2026 (the 30% 25D credit ended December 31, 2025). State costs range from **$17,300** (Hawaii) to **$86,500** (North Dakota).
Yes — same end goal, different starting point. $400/month maps to roughly **4,000 sq ft** nationally. Use this hub for **utility bills**; use the [4,000 sq ft hub](/guides/solar-panels-4000-sq-ft-house-by-state/) if you know home size.
See the [national $400/month guide](/guides/solar-panels-400-month-bill/) for roof orientation, panel wattage, and calculator walkthrough. Each state link below adds **local rate & sun hours**.
18.19¢/kWh — US average residential price. Source: EIA Electric Power Monthly, Table 5.6.B (year-to-date through July 2026), residential average retail price (July 2026) (EIA)
Solar production
4.5 peak sun hours/day × 0.82 system derate. Approximate state-average daily solar resource (peak sun hours) based on NREL solar resource data (NSRDB); not location-specific — use NREL PVWatts for an address-level estimate. (NREL PVWatts)
Installed price
$3.00 per watt before incentives. Blended 2026 US residential installed price used by this site; EnergySage marketplace reported about $2.60/W (mid-2026); full-market medians are higher.
Federal tax credit
$0 for homeowner-owned systems installed in 2026 — the 30% §25D credit ended Dec 31, 2025 (IRS)
Net metering
National blend — solar assumed to offset 75% of the bill (87% in full-retail net-metering states, 55–70% elsewhere).
Estimates only — not tax, legal or financial advice. Get at least three installer quotes and confirm incentives with your utility and a tax professional.