If you received a solar proposal in 2023 or 2024, there is a good chance it specified PERC panels. In 2026, many leading residential modules use a newer cell architecture called TOPCon. The change is real, but homeowners should understand where the improvement matters—and where marketing can overstate it.
What Changed From PERC to TOPCon?
For years, monocrystalline PERC was the solar industry's standard cell technology. Manufacturers have now shifted much of their production to n-type TOPCon, short for tunnel oxide passivated contact. TOPCon uses a thin passivating contact layer to reduce electrical losses inside the cell.
The transition has happened quickly. Market estimates differ depending on whether they measure factories, products, cells, or shipments, but the direction is clear. At the start of 2026, analysts cited by PV Tech estimated TOPCon represented almost 85% of global production, while other product-level surveys reported smaller shares. The careful conclusion is that TOPCon is now the dominant mainstream technology and PERC production is declining.
How Does TOPCon Help on a Residential Roof?
More rated power can fit into limited roof space
Current residential TOPCon modules commonly reach roughly 22% to 24% module efficiency, while many older PERC products fall closer to 20% to 22%. Exact figures depend on the manufacturer and model. Higher efficiency does not make a 10 kW system magically larger—a 10 kW TOPCon array and a 10 kW PERC array have the same nameplate capacity—but TOPCon may reach 10 kW with fewer panels or less roof area.
That distinction matters on shaded, segmented, or space-constrained roofs common in Philadelphia and the older neighborhoods of Montgomery, Delaware, Bucks, and Chester counties.
TOPCon generally loses slightly less output in high heat
Solar modules are rated at a cell temperature of 25°C, and output falls as cells get hotter. A typical power temperature coefficient might be around -0.29% to -0.32% per °C for TOPCon and around -0.34% to -0.38% per °C for many PERC modules. Always compare the actual datasheets; cell architecture alone does not guarantee a particular coefficient.
On a very hot roof, that difference can give TOPCon a modest instantaneous advantage over an otherwise comparable PERC module. It is generally a percentage point or two under those conditions—not a universal 3% to 5% improvement on every hot day.
Many TOPCon warranties promise stronger long-term output
Because n-type cells are less susceptible to some forms of light-induced degradation, many TOPCon manufacturers offer stronger linear performance warranties. Some guarantee approximately 87% to 90% of original rated output after 25 or 30 years. Those figures are warranty floors, not promises of exact real-world production, and they vary by product.
Compare the first-year allowance, annual degradation rate, final-year output, product warranty, labor coverage, and the financial strength of the company backing the warranty.
Will a 10 kW TOPCon System Produce Much More Than a 10 kW PERC System?
Not solely because it is TOPCon. Annual production depends primarily on system capacity, roof orientation, tilt, shade, weather, inverter design, clipping, and system losses. A well-sited 10 kW array in Southeastern Pennsylvania may produce roughly 11,000 to 14,000 kWh per year, but every home requires its own production model.
TOPCon can improve lifetime yield modestly through a better temperature coefficient, low-light response, and slower warranted degradation. Its larger benefit for many homeowners is fitting more nameplate capacity onto the usable roof. Claims that an equal-size TOPCon system automatically produces 8% to 12% more annual energy than PERC should be treated skeptically.
Does TOPCon Cost More in 2026?
At the module level, TOPCon pricing has moved close to mainstream PERC pricing in many supply channels as production scaled. A homeowner's installed price, however, includes far more than modules: engineering, racking, inverters, electrical work, permitting, interconnection, labor, warranties, and service all matter.
For Southeastern Pennsylvania, use a site-specific proposal rather than a national module-price chart. Pennstar Solar's current residential pricing and payback assumptions are explained on our solar cost and ROI page.
What Should You Ask an Installer About a Solar Panel?
- What is the exact manufacturer and model? “TOPCon” describes a cell architecture, not the overall quality of the module or warranty company.
- What are the module efficiency and temperature coefficient? Compare the actual datasheet rather than a sales summary.
- What do the product and performance warranties cover? Ask who pays labor, shipping, and removal if a module fails.
- How much annual production does the design model? The proposal should account for your roof orientation, shade, and equipment—not just a generic regional average.
What Is the Bottom Line on TOPCon Panels?
TOPCon is a meaningful evolution, not a reason to discard every PERC panel. A high-quality PERC system can still be an excellent investment, while a poorly supported TOPCon product is not automatically a better choice. For most new residential projects in 2026, TOPCon offers a strong combination of efficiency, heat performance, availability, and long-term warranty coverage.
Solar also crossed 3 TW of global installed capacity in 2026, showing how quickly the technology and its manufacturing base continue to mature.
Get a site-specific solar estimate from Pennstar Solar or call 610-900-6405.
