Solar Energy in Philadelphia, Pennsylvania

Average Solar Resource #18 nationally · #1 in Pennsylvania Pop. 1,603,797

Philadelphia, Pennsylvania receives 4.02 kWh/m²/day of solar irradiance and 4.7 peak sun hours daily, representing average solar resources . A typical 5 kW residential solar system in Philadelphia produces approximately 6,891 kWh annually, potentially saving homeowners $1,020 per year on electricity bills. After the 30% federal Investment Tax Credit, a 5 kW system has an estimated payback period of 10.3 years, leaving roughly 15 years of profitable operation within a standard 25-year warranty. For maximum annual output in Philadelphia, panels should be tilted at approximately 40° and oriented true south (180° azimuth).

Solar Resource Summary

4.02
kWh/m²/day
GHI Annual
4.7
hours/day
Peak Sun Hours
3.95
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) 2.05 2.95 3.96 4.87 5.62 5.9 5.97 5.2 4.33 3.2 2.25 1.86 4.02
DNI (kWh/m²/d) 3.32 4.01 4.25 4.28 4.33 4.29 4.54 4.12 4.11 3.76 3.14 3.25 3.95
Source: NREL. Monthly averages in kWh/m²/day and °C.

Solar Production Estimates for Philadelphia

5 kW Residential
Typical home system
Residential
6,891 kWh/yr
574 kWh/month avg
≈ $1,020/year savings
10 kW Residential
Large home system
Residential
13,782 kWh/yr
1,148 kWh/month avg
≈ $2,040/year savings
50 kW Commercial
Small commercial
Commercial
68,912 kWh/yr
5,743 kWh/month avg
100 kW Commercial
Medium commercial
Commercial
137,824 kWh/yr
11,485 kWh/month avg

Production estimates based on NREL solar resource data, 40° tilt, south-facing orientation, and 80% performance ratio.

Local Solar Conditions in Philadelphia

Philadelphia shows significant seasonal variation in solar output, with peak summer months receiving 6.0 kWh/m²/day compared to 1.9 kWh/m²/day in winter — a 3.2x difference. Battery storage or net metering is particularly valuable here.

Best Tilt Angle
40° (latitude-optimized)
Best Azimuth
180° (true south)
Coordinates
39.9526°N, -75.1652°

Financial Overview — Solar in Philadelphia

Solar is a sound investment in Philadelphia. A 10.3-year payback period is in line with the national average. With electricity rates likely to increase over time, actual payback may be shorter. Estimated annual savings from a 5 kW system: $1,020/year.

Avg. Electricity Rate
$0.148/kWh (PA avg)
Est. Annual Savings (5 kW)
$1,020/year
Est. Payback Period
10.3 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 — Philadelphia, Pennsylvania

In Philadelphia, Pennsylvania, a 5 kW residential solar system produces approximately 6,891 kWh of electricity per year. A 10 kW system produces about 13,782 kWh annually. These estimates use 4.0 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.

Philadelphia receives an average Global Horizontal Irradiance (GHI) of 4.02 kWh/m²/day. This is 0.48 kWh/m²/day below the US national average of 4.5 kWh/m²/day, placing Philadelphia 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.

Philadelphia, Pennsylvania receives an average of 4.7 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 Philadelphia produces 4.7 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.

Philadelphia is a average location for solar panels, with 4.02 kWh/m²/day solar irradiance — near the national average. It ranks #1 in Pennsylvania and #18 nationally for solar potential. With an estimated payback period of 10.3 years, solar installations in Philadelphia can be financially attractive, especially given Pennsylvania's electricity rates.

The optimal tilt angle for solar panels in Philadelphia is approximately 40°, 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° (55°). For maximum summer output, use latitude − 15° (25°). Fixed south-facing panels at the latitude angle are the standard recommendation for residential systems in Philadelphia.

A 5 kW solar system in Philadelphia can save an estimated $1,020 per year on electricity bills, based on Philadelphia's average electricity rate of $0.148/kWh. Over a 25-year system lifetime, that represents $25,500 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 10.3 years.

Philadelphia ranks #1 in Pennsylvania for solar potential based on annual GHI. This means 0 cities have higher solar irradiance in the state. As a top-ranked solar location, Philadelphia offers particularly strong economics for solar installations.Browse other Pennsylvania cities on our Pennsylvania solar data page to compare locations.

For a typical home in Philadelphia using 1,000 kWh/month, a 5 kW solar system producing 574 kWh/month would offset approximately 57% 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 Philadelphia has an estimated payback period of 10.3 years. This calculation assumes a net system cost of $10,500 (after the 30% federal ITC) and annual savings of $1,020. Modern solar panels carry 25-year performance warranties, so systems in Philadelphia would operate profitably for roughly 15 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

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Quick Stats

Annual GHI
4.02 kWh/m²/day
Peak Sun Hours
4.7 h/day
5kW Production
6,891 kWh/yr
Payback (5kW)
10.3 years
Rank in Pennsylvania
#1
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