Solar Panel Calculator for Portland, ME
Estimate the cost, savings and payback of solar panels in Portland, ME, using local NREL sunshine data, Maine prices and electricity rates.
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Portland gets about 4.59 peak sun hours a day on a south-facing roof, so each kW of panels makes about 1,332 kWh a year. That ranks #83 of the 111 cities on this site. Output peaks in Aug and is lowest in Dec.
Sunshine in Portland by month
What an 8 kW system makes in Portland
| Month | Sun hours a day | Output | Bill savings |
|---|---|---|---|
| Jan | 2.96 | 640 kWh | $193 |
| Feb | 3.90 | 744 kWh | $225 |
| Mar | 4.91 | 1,016 kWh | $307 |
| Apr | 5.79 | 1,120 kWh | $339 |
| May | 5.73 | 1,112 kWh | $336 |
| Jun | 5.91 | 1,072 kWh | $324 |
| Jul | 5.99 | 1,112 kWh | $336 |
| Aug | 6.04 | 1,128 kWh | $341 |
| Sep | 5.21 | 968 kWh | $293 |
| Oct | 3.60 | 728 kWh | $220 |
| Nov | 2.68 | 544 kWh | $164 |
| Dec | 2.35 | 496 kWh | $150 |
| Year | 4.59 | 10,656 kWh | $3,221 |
Savings at 30.23¢ per kWh (Maine average), with every kWh credited at that price.
Cost and payback by system size
At $2.91 per watt, the Maine average, before incentives.
| System | Cost | Year 1 savings | Payback | 25-yr gain |
|---|---|---|---|---|
| 4 kW | $11,640 | $1,611 | 7.3 yrs | $26,300 |
| 6 kW | $17,460 | $2,416 | 7.3 yrs | $39,451 |
| 8 kW | $23,280 | $3,221 | 7.3 yrs | $52,601 |
| 10 kW | $29,100 | $4,027 | 7.3 yrs | $65,751 |
| 12 kW | $34,920 | $4,832 | 7.3 yrs | $78,901 |
How many panels you need in Portland
| Monthly use | System | 400 W panels |
|---|---|---|
| 500 kWh | 4.50 kW | 12 |
| 750 kWh | 6.76 kW | 17 |
| 1,000 kWh | 9.01 kW | 23 |
| 1,500 kWh | 13.51 kW | 34 |
| 2,000 kWh | 18.02 kW | 46 |
Covering 100% of a year's use at 1,332 kWh per kW.
Common questions
Is solar worth it in Portland?
At local averages an 8 kW system costs about $23,280 before incentives, saves about $3,221 in its first year and pays back in about 7.3 years.
How many peak sun hours does Portland get?
About 4.59 a day over the year on a south-facing roof at 20°, from 2.4 in Dec to 6.0 in Aug, according to NREL's PVWatts model.
How much does a 1 kW solar system produce in Portland?
About 1,332 kWh a year, or 111 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