Solar Panel Calculator for Wilmington, DE
Estimate the cost, savings and payback of solar panels in Wilmington, DE, using local NREL sunshine data, Delaware prices and electricity rates.
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Wilmington gets about 4.80 peak sun hours a day on a south-facing roof, so each kW of panels makes about 1,364 kWh a year. That ranks #69 of the 111 cities on this site. Output peaks in Jul and is lowest in Dec.
Sunshine in Wilmington by month
What an 8 kW system makes in Wilmington
| Month | Sun hours a day | Output | Bill savings |
|---|---|---|---|
| Jan | 2.95 | 616 kWh | $111 |
| Feb | 3.89 | 728 kWh | $131 |
| Mar | 4.96 | 1,008 kWh | $181 |
| Apr | 5.71 | 1,072 kWh | $193 |
| May | 5.90 | 1,104 kWh | $198 |
| Jun | 6.10 | 1,088 kWh | $196 |
| Jul | 6.37 | 1,160 kWh | $209 |
| Aug | 5.98 | 1,088 kWh | $196 |
| Sep | 5.31 | 960 kWh | $173 |
| Oct | 4.07 | 800 kWh | $144 |
| Nov | 3.65 | 720 kWh | $129 |
| Dec | 2.69 | 560 kWh | $101 |
| Year | 4.80 | 10,912 kWh | $1,962 |
Savings at 17.98¢ per kWh (Delaware average), with every kWh credited at that price.
Cost and payback by system size
At $2.63 per watt, the Delaware average, before incentives.
| System | Cost | Year 1 savings | Payback | 25-yr gain |
|---|---|---|---|---|
| 4 kW | $10,520 | $981 | 11.0 yrs | $12,588 |
| 6 kW | $15,780 | $1,471 | 11.0 yrs | $18,882 |
| 8 kW | $21,040 | $1,962 | 11.0 yrs | $25,176 |
| 10 kW | $26,300 | $2,452 | 11.0 yrs | $31,470 |
| 12 kW | $31,560 | $2,943 | 11.0 yrs | $37,764 |
How many panels you need in Wilmington
| Monthly use | System | 400 W panels |
|---|---|---|
| 500 kWh | 4.40 kW | 11 |
| 750 kWh | 6.60 kW | 17 |
| 1,000 kWh | 8.80 kW | 22 |
| 1,500 kWh | 13.20 kW | 33 |
| 2,000 kWh | 17.60 kW | 44 |
Covering 100% of a year's use at 1,364 kWh per kW.
Common questions
Is solar worth it in Wilmington?
At local averages an 8 kW system costs about $21,040 before incentives, saves about $1,962 in its first year and pays back in about 11.0 years.
How many peak sun hours does Wilmington get?
About 4.80 a day over the year on a south-facing roof at 20°, from 2.7 in Dec to 6.4 in Jul, according to NREL's PVWatts model.
How much does a 1 kW solar system produce in Wilmington?
About 1,364 kWh a year, or 114 kWh a month on average.
Is there a federal solar tax credit?
Not for homeowners who buy their system. The 30% Residential Clean Energy Credit ended for systems installed after December 31, 2025.
Sources
- NREL PVWatts V8 API (south-facing, 20° tilt, 14% losses, typical-year weather): https://developer.nlr.gov/docs/solar/pvwatts/v8/
- EnergySage, Solar panel cost by state (updated November 6, 2026): https://www.energysage.com/local-data/solar-panel-cost/
- U.S. EIA, Electric Power Monthly, Table 5.6.B (residential price, Jan–Aug 2026): https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_b