Solar Energy in Portland, Maine

Average Solar Resource Pop. 68,408

Portland, Maine receives 3.83 kWh/m²/day of solar irradiance and 4.6 peak sun hours daily, representing average solar resources . A typical 5 kW residential solar system in Portland produces approximately 6,760 kWh annually, potentially saving homeowners $1,480 per year on electricity bills. After the 30% federal Investment Tax Credit, a 5 kW system has an estimated payback period of 7.1 years, leaving roughly 18 years of profitable operation within a standard 25-year warranty. For maximum annual output in Portland, panels should be tilted at approximately 44° and oriented true south (180° azimuth).

Solar Resource Summary

3.83
kWh/m²/day
GHI Annual
4.6
hours/day
Peak Sun Hours
4.14
kWh/m²/day
DNI Annual
GHI vs. US national average (4.5 kWh/m²/day) Average
0 7.5 kWh/m²/day

Monthly Solar Data

Month JanFebMarAprMayJunJulAugSepOctNovDec Annual
GHI (kWh/m²/d) 1.82 2.65 3.7 4.85 5.44 5.65 5.93 5.36 4.33 2.84 1.8 1.55 3.83
DNI (kWh/m²/d) 3.31 3.83 4.17 4.75 4.6 4.44 5.14 5.12 4.87 3.63 2.75 3.03 4.14
Source: NREL. Monthly averages in kWh/m²/day and °C.

Solar Production Estimates for Portland

5 kW Residential
Typical home system
Residential
6,760 kWh/yr
563 kWh/month avg
≈ $1,480/year savings
10 kW Residential
Large home system
Residential
13,520 kWh/yr
1,127 kWh/month avg
≈ $2,960/year savings
50 kW Commercial
Small commercial
Commercial
67,598 kWh/yr
5,633 kWh/month avg
100 kW Commercial
Medium commercial
Commercial
135,196 kWh/yr
11,266 kWh/month avg

Production estimates based on NREL solar resource data, 44° tilt, south-facing orientation, and 80% performance ratio.

Local Solar Conditions in Portland

Portland shows significant seasonal variation in solar output, with peak summer months receiving 5.9 kWh/m²/day compared to 1.6 kWh/m²/day in winter — a 3.8x difference. Battery storage or net metering is particularly valuable here.

Best Tilt Angle
44° (latitude-optimized)
Best Azimuth
180° (true south)
Coordinates
43.6591°N, -70.2568°

Financial Overview — Solar in Portland

Solar is an excellent investment in Portland. With a 7.1-year payback on a 5 kW system and 25-year panel warranties, early adopters in Portland can expect 15+ years of net profit. Estimated annual savings from a 5 kW system: $1,480/year.

Avg. Electricity Rate
$0.219/kWh (ME avg)
Est. Annual Savings (5 kW)
$1,480/year
Est. Payback Period
7.1 years (after 30% ITC)
Federal ITC
30% of system cost
Net Metering
Available
Financial estimates assume a 5 kW system at $3,000/W installed ($15,000 pre-ITC, $10,500 after 30% credit). Actual costs vary by installer and equipment. Consult a local solar installer for firm quotes.

Solar FAQ — Portland, Maine

In Portland, Maine, a 5 kW residential solar system produces approximately 6,760 kWh of electricity per year. A 10 kW system produces about 13,520 kWh annually. These estimates use 3.8 kWh/m²/day average solar irradiance and an 80% system performance ratio, accounting for real-world losses from wiring, inverter efficiency, and temperature. Actual output will vary based on your specific roof orientation, shading, and equipment.

Portland receives an average Global Horizontal Irradiance (GHI) of 3.83 kWh/m²/day. This is 0.67 kWh/m²/day below the US national average of 4.5 kWh/m²/day, placing Portland near the national average. GHI measures total solar energy incident on a horizontal surface and is the primary indicator of a location's solar resource quality.

Portland, Maine receives an average of 4.6 peak sun hours per day. Peak sun hours represent the equivalent number of hours when solar irradiance equals 1,000 W/m² — the standard condition used to rate solar panel output. This means a 1 kW solar panel array in Portland produces 4.6 kWh on a typical day. Seasonal variation is significant: summer months see peak sun hours 40–60% higher than winter months in most US locations.

Portland is a average location for solar panels, with 3.83 kWh/m²/day solar irradiance — near the national average. With an estimated payback period of 7.1 years, solar installations in Portland can be financially attractive, especially given Maine's electricity rates.

The optimal tilt angle for solar panels in Portland is approximately 44°, which corresponds to the city's latitude. This angle maximizes annual energy production by ensuring panels receive the most direct sunlight averaged over the year. For maximum winter output, tilt panels at latitude + 15° (59°). For maximum summer output, use latitude − 15° (29°). Fixed south-facing panels at the latitude angle are the standard recommendation for residential systems in Portland.

A 5 kW solar system in Portland can save an estimated $1,480 per year on electricity bills, based on Portland's average electricity rate of $0.219/kWh. Over a 25-year system lifetime, that represents $37,000 in total savings before accounting for electricity rate increases. After the 30% federal Investment Tax Credit, the net system cost of approximately $10,500 for a 5 kW system yields a payback period of 7.1 years.

For a typical home in Portland using 1,000 kWh/month, a 5 kW solar system producing 563 kWh/month would offset approximately 56% of a typical household's electricity use. Most residential installations in similar climates range from 5 to 12 kW depending on energy consumption, roof size, and budget. Use SolarScope's Site Studio to get a personalized system size recommendation based on your specific address and energy bills.

Based on local solar irradiance and electricity rates, a 5 kW residential solar system in Portland has an estimated payback period of 7.1 years. This calculation assumes a net system cost of $10,500 (after the 30% federal ITC) and annual savings of $1,480. Modern solar panels carry 25-year performance warranties, so systems in Portland would operate profitably for roughly 18 years after payback. Electricity rate increases over time typically reduce the effective payback period.
Learn more: Solar irradiance · Peak sun hours · GHI explained · Net metering · How solar analysis works

Get a Detailed Solar Analysis for Portland

This page shows area-level averages. For your specific address — accounting for roof orientation, shading trees, and your utility rate — use SolarScope's AI-powered Site Studio.

Open Site Studio Community Data for Maine

Quick Stats

Annual GHI
3.83 kWh/m²/day
Peak Sun Hours
4.6 h/day
5kW Production
6,760 kWh/yr
Payback (5kW)
7.1 years
Analyze your Portland address

Get precise production estimates for your roof

Open Site Studio
← Maine solar data ← All states