Solar in Delaware: payback, sun by city and utility-scale capacity
Across 4 Delaware cities, yearly output runs from 1,364 kWh per kW in Wilmington to 1,414 in Seaford. Jul is the best month at 148 kWh per kW and Dec the worst at 72. Delaware pays back in 12.7 years at $3.00 a watt (rank 21 of 51), 0.8 years shorter than the middle state. 1,383 kWh per kW (rank 23) at 17.13 ¢ (rank 18 from the top): sun and price equally drives it. Utility-scale solar in Delaware: 115 MW in 20 plants, 3.1% of 2025 generation; 208 MW more under construction or planned.
Sun inside Delaware: 4 cities, 4% apart
| Delaware city | kWh per kW a year | Against state point | Sun, kWh/m2 a day | Payback at $3.00 | Residents |
|---|---|---|---|---|---|
| Wilmington | 1,364 | -1.4% | 4.80 | 12.8 | 71,124 |
| Dover | 1,398 | +1.1% | 4.92 | 12.5 | 39,491 |
| Seaford | 1,414 | +2.2% | 4.97 | 12.4 | 8,255 |
| South Bethany | 1,400 | +1.2% | 4.86 | 12.5 | 503 |
Delaware state point 39.40, -75.57; city points Wilmington 39.74, -75.53; Dover 39.16, -75.52; Seaford 38.66, -75.61; South Bethany 38.52, -75.06. Panel and method: solar method.
Output by month in Delaware cities: 12 rows
| Delaware month | Wilmington | Dover | Seaford | South Bethany |
|---|---|---|---|---|
| Jan | 77.4 | 85.5 | 87.5 | 76.1 |
| Feb | 90.9 | 95.4 | 91.8 | 94.0 |
| Mar | 125.5 | 112.2 | 130.1 | 123.1 |
| Apr | 134.0 | 139.0 | 141.4 | 141.4 |
| May | 138.1 | 148.6 | 148.6 | 151.3 |
| Jun | 136.0 | 138.3 | 140.2 | 146.0 |
| Jul | 145.3 | 147.7 | 149.2 | 149.4 |
| Aug | 136.3 | 142.2 | 133.1 | 139.1 |
| Sep | 119.8 | 121.5 | 118.6 | 118.6 |
| Oct | 99.8 | 107.3 | 107.3 | 107.0 |
| Nov | 90.1 | 85.1 | 94.9 | 81.9 |
| Dec | 70.3 | 75.5 | 70.8 | 71.4 |
Delaware: 4 cities, best month 151 and worst 70 kWh per kW across them.
CSVBest and worst month in Delaware: Jul 148, Dec 72 kWh per kW
| Delaware month | kWh per kW | Price ¢ | Value per kW | kWh per kW per sun unit |
|---|---|---|---|---|
| Jan | 84.4 | 15.53 | $13.11 | 0.85 |
| Feb | 94.4 | 15.65 | $14.77 | 0.83 |
| Mar | 125.9 | 16.71 | $21.04 | 0.82 |
| Apr | 137.1 | 17.97 | $24.64 | 0.79 |
| May | 145.1 | 18.13 | $26.31 | 0.76 |
| Jun | 139.8 | 18.16 | $25.39 | 0.75 |
| Jul | 147.6 | 16.58 | $24.47 | 0.74 |
| Aug | 131.9 | 16.82 | $22.19 | 0.74 |
| Sep | 117.4 | 18.12 | $21.27 | 0.76 |
| Oct | 105.3 | 18.31 | $19.28 | 0.79 |
| Nov | 82.2 | 18.81 | $15.46 | 0.82 |
| Dec | 72.3 | 17.12 | $12.38 | 0.84 |
Delaware: December to February give 18% of a year (rank 26 of 51, 1 = most winter); the best month is 2.0 times the worst. Output per unit of sun is highest in Jan (0.85) and lowest in Jul (0.74); PVWatts lowers cell output when the panel is hot, and the sun angle changes with the season. Our runs use one fixed 14% loss figure for every place, so snow or soiling in Delaware is not modelled separately.
Delaware: payback 12.7 years, rank 21 of 51
| Measure | Value | Rank of 51 | Median state |
|---|---|---|---|
| Output of 1 kW a year, kWh | 1,383 | 23 | 1,372 |
| Home price, ¢ per kWh | 17.13 | 18 | 15.37 |
| Value of 1 kW a year | $237 | 21 | $222 |
| Payback at $3.00 a watt | 12.7 years | 21 | 13.5 years |
EIA-861 (2024): 14,174 home net-metered systems in Delaware, 29.9 per 1,000 accounts (rank 15), average 8.0 kW.
Utility-scale solar in Delaware: 115 MW
Delaware: 115 MW of operable utility-scale solar in 20 plants across 3 counties (EIA-860, 2025), rank 47 of 51; 114 W per resident, rank 43. Solar made 3.1% of Delaware's net generation in 2025 (EIA-923), rank 30, -3.7 points against the national share. Biggest plants: ENGIE Solidago Solar Project - Hybrid in New Castle County, 50 MW (2022); Milford Solar Farm in Kent County, 12 MW (2012); Dover Sun Park in Kent County, 10 MW (2011). By county: New Castle 58 MW, Kent 37 MW, Sussex 20 MW. Proposed: 29 MW under construction (9 plants) and 178 MW planned (6 plants); batteries 0 MW running and 0 MW proposed.
| Delaware year | MW added | Cumulative share of today's MW |
|---|---|---|
| 2019 | 3 | 3% |
| 2020 | 0 | 3% |
| 2021 | 1 | 4% |
| 2022 | 52 | 49% |
| 2023 | 0 | 49% |
| 2024 | 8 | 55% |
| 2025 | 17 | 71% |
Sizes and prices per watt in Delaware
| Delaware kW | kWh a year | Value a year | Cost at $2.50 | At $3.00 | At $3.50 | t CO2 |
|---|---|---|---|---|---|---|
| 4 | 5,533 | $948 | $10,000 | $12,000 | $14,000 | 1.8 |
| 6 | 8,299 | $1,422 | $15,000 | $18,000 | $21,000 | 2.6 |
| 8 | 11,066 | $1,896 | $20,000 | $24,000 | $28,000 | 3.5 |
| 10 | 13,832 | $2,369 | $25,000 | $30,000 | $35,000 | 4.4 |
| 12 | 16,598 | $2,843 | $30,000 | $36,000 | $42,000 | 5.3 |
| Delaware $ per watt | 100% retail | 75% | 50% | 25% |
|---|---|---|---|---|
| $2.00 | 8.4 | 11.3 | 16.9 | 33.8 |
| $2.50 | 10.6 | 14.1 | 21.1 | 42.2 |
| $3.00 | 12.7 | 16.9 | 25.3 | 50.6 |
| $3.50 | 14.8 | 19.7 | 29.5 | 59.1 |
| $4.00 | 16.9 | 22.5 | 33.8 | 67.5 |
Delaware: 1,383 kWh/kW × 17.13 ¢ = 237 a year per kW; the 30% column (8.9 years at $3.00) is arithmetic only.
CSVNet metering and CO2 in Delaware
EIA-861 (2024): 14,174 home net-metered systems in Delaware, 29.9 per 1,000 accounts (rank 15), average 8.0 kW.
6 kW in Delaware: 8,299 kWh a year displaces 2.6 t CO2 at 0.319 kg per kWh, -0.4 t against the average state.
Delaware among its neighbours
| Closest to Delaware | Payback, years | kWh per kW | Price, ¢ | Utility-scale solar, points of generation | Miles away |
|---|---|---|---|---|---|
| Delaware (this page) | 12.7 | 1,383 | 17.13 | 3.1 | - |
| Maryland | -1.6 | +4 | +2.35 | +0.3 | 69 |
| District of Columbia | -2.8 | +8 | +4.81 | +15.3 | 85 |
| New Jersey | -2.6 | -60 | +5.50 | -0.5 | 97 |
| Pennsylvania | -0.1 | -142 | +2.17 | -2.4 | 98 |
Delaware against its neighbours in the payback ranking
- -1 places, Pennsylvania -0.1 years against Delaware
- +0 places, Nevada -0.1 years against Delaware
- Delaware, rank 21: 12.7 years
- +2 places, Florida +0.1 years against Delaware
- +3 places, Texas +0.3 years against Delaware
Delaware utilities and solar payback
| Delaware utility | Homes | Price ¢ | Value of 1 kW | Payback at $3.00 |
|---|---|---|---|---|
| Delmarva Power | 301,950 | 16.37 | $226 | 13.2 yr |
| Delaware Electric Cooperative | 104,839 | 14.22 | $197 | 15.3 yr |
| City of Dover | 21,601 | 15.52 | $215 | 14.0 yr |
| City of Newark | 11,888 | 18.99 | $263 | 11.4 yr |
| Town of Middletown | 9,071 | 17.12 | $237 | 12.7 yr |
| City of Milford | 7,169 | 15.17 | $210 | 14.3 yr |
Your numbers for Delaware
Limits in Delaware
Delaware: with the old 30% credit (IRS, ended 2025) payback would be 8.9 years instead of 12.7, so the calculator starts at 0%. No Delaware export rates in our data: output counts at 17.13 ¢. All limits.
Sources for Delaware
- PVWatts v8 (NLR), 4 Delaware cities and one state point: 1,383 kWh per kW
- EIA-860 2025 and EIA-923 2025: 115 MW of solar in Delaware
- EIA-861 2024: 14,174 net-metered systems in Delaware
- EIA retail sales 2025: 17.13 ¢ per kWh in Delaware
- IRS 25D (ended 2025): 8.9 years in Delaware with it; licences and periods for Delaware
More about Delaware
Delaware electricity hub, Delaware EV charging: 229 stations, where Delaware ranks for rooftop solar, 12.7 years against 51 states, Delaware calculators.
Questions
Where in Delaware is solar best?
Yes: 4% between Wilmington and Seaford in yearly output.
Delaware utility-scale solar capacity?
115 MW in 20 plants (EIA-860), 114 W per resident, rank 43; 208 MW proposed.
Net metering in Delaware?
14,174 systems, 29.9 per 1,000 accounts, rank 15.
Solar payback in Delaware?
12.7 years at $3.00 a watt; 10.6 at $2.50; 14.8 at $3.50; 1,383 kWh per kW at 17.13 ¢.
Delaware electricity from solar, what share?
3.1% of 2025 net generation, rank 30 of 51, -3.7 points against the nation.
Delaware sunshine for solar panels?
1,383 kWh per kW a year at the state point, rank 23 of 51; from 1,364 in Wilmington to 1,414 in Seaford.
Winter cut in Delaware solar output?
December to February give 18% of the year; Jul makes 148 kWh per kW and Dec 72.
Delaware pays half price for exports?
Payback 25.3 years at a 50% retail share.
CO2 displaced in Delaware?
2.6 t a year on 6 kW at 0.319 kg per kWh.
Federal solar credit in Delaware: still available?
Ended 2025 (IRS 25D); with it Delaware payback would be 8.9 years, not 12.7.