Solar Panel Climate Simulator

Solar panels are rated at Standard Test Conditions (STC) of 25°C, but rooftop solar cells routinely reach 50–70°C during summer months. The temperature coefficient tells you how much output drops for every degree Celsius above 25°C. For example, a standard PERC panel with a coefficient of −0.34%/°C loses 0.34% of its rated power per degree above STC. An HJT panel at −0.24%/°C loses only 0.24% per degree. The difference compounds in hot climates: at a cell temperature of 65°C (40 degrees above STC), a −0.34 panel loses 13.6% of rated output while a −0.24 panel loses only 9.6%. That 4-percentage-point gap translates directly into more kilowatt-hours produced on every hot day, making temperature coefficient one of the most important specs for homeowners in warm climates like Texas, Florida, or the Southeast.

Climate affects solar production through two primary mechanisms: solar radiation and temperature. Solar radiation (measured in peak sun hours) determines how much sunlight reaches your panels. Boston averages about 4.2 peak sun hours per day while Dallas averages roughly 5.0, meaning Dallas receives about 19% more raw solar energy. However, temperature works against production — hotter climates cause panels to lose efficiency. Dallas panels lose more to heat penalties than Boston panels, partially offsetting the extra sunlight. The net production difference depends on the specific panel specs. Cloud cover, humidity, and snow also factor in: humid climates scatter more sunlight (reducing direct irradiance), while snow temporarily blocks panels in winter but can also reflect additional light onto cleared panels. This simulator uses real NREL weather data for your ZIP code to account for all of these factors.

All solar panels gradually lose output capacity as the silicon cells age through a process called degradation. Every manufacturer publishes a degradation rate and a year-25 performance guarantee. Standard Mono PERC panels typically degrade at about 0.5% per year, guaranteeing 86% of original output at year 25. Premium N-type TOPCon panels degrade at approximately 0.4% per year, guaranteeing around 88–89% at year 25. Top-tier HJT panels degrade the slowest at roughly 0.33% per year, with manufacturers like REC guaranteeing 92% at year 25. While a 6-percentage-point difference between 86% and 92% sounds small, it compounds significantly over the life of the system. On a 10 kW system producing 12,000 kWh in year one, that gap means approximately 7,200 extra kWh over 25 years — worth $1,800–$2,100 at typical electricity rates. The simulator models degradation year by year for each panel so you can see the cumulative impact.

These are the three cell technologies available in residential solar panels today, each representing a different generation of silicon solar engineering. Mono PERC (Passivated Emitter Rear Cell) is the most mature and widely deployed technology, powering about 70% of residential installations. PERC panels offer proven reliability, the lowest installed cost, and typical efficiencies around 20–21%. N-type TOPCon (Tunnel Oxide Passivated Contact) is the current next-generation technology. TOPCon cells use an ultra-thin tunnel oxide layer on the rear surface to reduce electron recombination, achieving higher efficiencies of 21–22%, lower degradation, and slightly better temperature performance than PERC. TOPCon panels cost moderately more but deliver measurably better lifetime production. HJT (Heterojunction Technology) combines crystalline silicon with thin layers of amorphous silicon, creating the best temperature coefficient (−0.24 to −0.26%/°C) and lowest degradation of any commercial cell type. HJT panels reach 22–22.5% efficiency and carry the highest price premium. Each technology involves trade-offs between upfront cost, efficiency, degradation rate, and temperature performance.

HJT panels are the strongest performers in hot climates thanks to their superior temperature coefficients. Panels like the REC Alpha Pure-RX (−0.24%/°C) and Silfab SIL-440 (−0.26%/°C) retain more of their rated output when cell temperatures climb above 25°C. In Texas or Florida, where rooftop cell temperatures regularly exceed 60°C during summer, an HJT panel produces roughly 3–4% more annual energy than a PERC panel of similar wattage. That translates to an extra 350–500 kWh per year on a typical 10 kW system. However, HJT panels also carry a price premium of $0.15–$0.20 per watt over standard PERC panels. Whether the premium pays for itself depends on your electricity rate, system size, and how hot your climate actually gets. Our simulator calculates the exact production difference for your ZIP code so you can make a data-driven decision rather than relying on generic recommendations.

The climate data powering this simulator comes from NREL PVWatts, which uses TMY (Typical Meteorological Year) datasets compiled from 30+ years of ground-based weather station measurements across the United States. Monthly temperature data comes from NOAA Climate Normals. The simulation applies each manufacturer’s published specifications — efficiency, temperature coefficient, and degradation rate — to the irradiance and temperature data for your specific location. Real-world production will vary based on several factors this tool does not model: roof pitch and azimuth, shading from trees or neighboring structures, soiling and snow coverage, inverter clipping losses, and wiring losses. Because of these variables, the simulator is best used for comparing relative panel performance rather than predicting exact annual production. It answers the question "how do these panels compare in MY climate?" with high confidence, even though absolute kWh numbers will differ from a site-specific engineering analysis. For a production estimate based on your actual roof, use our IQ tool.

This simulator is designed to compare how panels perform relative to each other in your climate — it is not a system sizing tool. Proper system sizing requires your actual electricity usage (ideally 12 months of utility bills), roof measurements including pitch, azimuth, and available area, a shading analysis using satellite imagery or on-site assessment, and local utility rate structures. Our IQ tool at /iq uses satellite imagery of your actual roof to provide a personalized system design and production estimate. The simulator helps you answer a different but equally important question: which panel technology makes the most sense for your climate BEFORE you get a full quote. Many homeowners find it useful to run the simulator first, understand the panel trade-offs, and then request a quote already knowing which panel tier fits their priorities.

Yes. Every panel in this simulator is one we actively install across our service areas in New England and the Mid-Atlantic. We carry this range because different homes, budgets, and priorities require different solutions. Approximately 60% of our residential installations use the QCells Q.PEAK DUO BLK ML-G10+ (410W) because it delivers the best installed price per watt and is manufactured in Georgia, USA. About 15% of customers upgrade to the QCells Q.TRON (435W, N-type TOPCon) for better long-term performance. Premium projects frequently use the REC Alpha Pure-RX (460W) for maximum efficiency or the Silfab SIL-440 for its industry-leading 30-year warranty. Specialty applications like ground-mounted bifacial systems use the SEG Solar SEG-440. Our NABCEP-certified installation team can recommend the best panel for your specific situation after an on-site or satellite-based assessment.