Pennsylvania Solar Panel Performance Benchmarks

Last updated: 2026-04-08 · Solar Benchmark

Pennsylvania Solar Panel Performance Benchmarks

A correctly installed 6 kW south-facing system at 30-degree tilt in Philadelphia produces approximately 7,980 kWh per year, equal to a specific yield of 1,330 kWh/kW/year. Pittsburgh sits significantly lower at around 1,180 kWh/kW/year due to its river valley topography and persistent cloud cover. Erie, affected by Lake Erie lake-effect weather, averages roughly 1,120 kWh/kW/year, the lowest specific yield among major Pennsylvania cities.

Monthly Production Benchmarks

Reference system: 6 kW, south-facing, 30-degree tilt, Philadelphia (40.0°N). Source: pvlib physics modeling, Open-Meteo ERA5 weather data.

Month	Est. Production (kWh)	Daily Average (kWh/day)
January	340	11.0
February	460	16.4
March	650	21.0
April	790	26.3
May	880	28.4
June	920	30.7
July	910	29.4
August	860	27.7
September	730	24.3
October	570	18.4
November	390	13.0
December	310	10.0
Annual Total	7,810	21.4

Note: Monthly values scaled to approximate the ~1,330 kWh/kW specific yield benchmark for Philadelphia. Actual production varies with panel brand, shading, soiling, and inverter efficiency. These figures represent physics-derived benchmarks for a well-installed system with no shading losses.

Annual Benchmarks by System Size and Region

Estimated annual production (kWh) by system size and Pennsylvania region. Based on pvlib modeling with Open-Meteo ERA5 climate data.

System Size	Philadelphia	Pittsburgh	Harrisburg	Allentown	Erie	Reading
4 kW	5,320	4,720	5,160	5,200	4,480	5,240
6 kW	7,980	7,080	7,740	7,800	6,720	7,860
8 kW	10,640	9,440	10,320	10,400	8,960	10,480
10 kW	13,300	11,800	12,900	13,000	11,200	13,100
12 kW	15,960	14,160	15,480	15,600	13,440	15,720

Climate Zones and Performance Ratio Targets

Climate Zone	Representative City	Specific Yield (kWh/kW/yr)	Performance Ratio Target
Humid Continental (SE)	Philadelphia	1,330	0.79-0.84
Humid Continental (central)	Harrisburg	1,290	0.79-0.84
Humid Continental (Lehigh Valley)	Allentown	1,300	0.79-0.84
River Valley (SW, very cloudy)	Pittsburgh	1,180	0.79-0.84
Lake Effect (NW)	Erie	1,120	0.79-0.84

The 210 kWh/kW/year gap between Philadelphia (1,330) and Erie (1,120) is one of the largest intrastate specific yield differences in the Northeast. Using statewide averages for Pennsylvania produces benchmarks that are wrong for both extremes. Always use city-specific data when evaluating a PA system.

What Affects Pennsylvania Solar Output

Pittsburgh's exceptional cloudiness: Pittsburgh averages only 59 sunny days per year, placing it among the cloudiest major cities in the United States. The combination of river valley topography, industrial history, and frequent frontal weather systems creates persistent overcast conditions. Pittsburgh receives approximately 11% less annual solar resource than Philadelphia and 6% less than Harrisburg. Systems in Allegheny County should be benchmarked against Pittsburgh-specific data, not statewide figures.
Lake Erie effect on northwest Pennsylvania: Erie sits directly downwind of Lake Erie. Lake-effect clouds and precipitation reduce Erie's annual solar resource to approximately 1,120 kWh/kW/year, the lowest in the state. The effect is most severe November through January. By summer, Erie's solar resource partially recovers and approaches other Pennsylvania locations, but the winter deficit drags annual production significantly below state averages.
Philadelphia urban heat island: Philadelphia's urban density and paved surfaces raise ambient temperatures 2-4°C above surrounding suburban areas. This marginally increases panel operating temperatures and produces a small thermal derating effect, typically 1-2% annually. The effect is minor relative to the city's strong solar resource from its southeastern location and proximity to the Atlantic coastal plain.
Net metering policy context: Pennsylvania's successor to Act 129 provides one-to-one net metering credit for excess production. This policy makes accurate production benchmarking valuable: knowing whether a system is producing correctly determines whether a homeowner is receiving the full net metering benefit they paid for at installation.
Seasonal trough depth: December through February are severely cloud-limited for all Pennsylvania locations. A 6 kW Philadelphia system produces roughly 340 kWh in January and 310 kWh in December, compared to 920 kWh in June. This 2.7:1 summer-to-winter ratio is more extreme than mid-Atlantic states further south and requires appropriate expectations during winter monitoring.

Frequently Asked Questions

What is a good annual output for a 6 kW system in Pennsylvania?

Expected annual output depends heavily on location within Pennsylvania. Philadelphia and Reading systems should produce 7,700-8,200 kWh per year. Harrisburg and Allentown systems target 7,500-8,000 kWh. Pittsburgh systems should produce 6,800-7,400 kWh, and Erie systems 6,400-7,000 kWh. Using statewide averages for any Pennsylvania location produces the wrong benchmark, given the wide variation across the state.

Why is Pittsburgh so much less productive than Philadelphia for solar?

Pittsburgh receives roughly 11% less annual solar radiation than Philadelphia. Three factors combine: river valley topography that traps fog and cloud; higher frequency of overcast frontal weather systems moving in from the Ohio Valley; and greater distance from the Atlantic coastal plain, which benefits southeastern PA with slightly more stable, clearer air. At the same system size, a Philadelphia installation produces roughly 900 kWh more per year than a Pittsburgh installation.

Does Pennsylvania's net metering policy affect how I should monitor my system?

Yes. Under net metering, kilowatt-hours you export to the grid offset future bills at the retail rate. Every kWh a malfunctioning system fails to produce is a kWh you buy back at retail instead of generating for free. Accurate monthly benchmarking, comparing your actual monitoring data to physics-based benchmarks for your specific location, lets you catch underperformance early, before it accumulates into a costly annual deficit.

How do I get an independent benchmark for my Pennsylvania system?

Enter your system's location, size, tilt, and azimuth at solarbenchmark.io. The tool runs pvlib physics modeling against Open-Meteo ERA5 historical weather data for your exact coordinates, producing a monthly production benchmark you can compare directly to your inverter or utility monitoring data. See the full methodology for data sources and assumptions.

Data: pvlib physics modeling + Open-Meteo ERA5 weather data | Last updated: 2026-04-08 | Solar Benchmark