--- title: "TOPCon or PERC solar panels: which to buy? | ComparePV" description: "TOPCon or PERC? Efficiency, heat losses, warranted ageing and price per watt compared across our module catalogue and live Polish shop offers." source: "https://comparepv.com/articles/topcon-or-perc" image: "https://comparepv.com/static/images/og/articles/topcon-or-perc.jpg" updated: 2026-10-09 --- # TOPCon or PERC when buying today? TOPCon or PERC? Efficiency, heat losses, warranted ageing and price per watt compared across our module catalogue and live Polish shop offers. By [Bart Szablowski](https://comparepv.com/authors/bart-szablowski) · Updated 9 October 2026 · 9 min read ## The analysis On this page 1. How the two groups were built 2. TOPCon vs PERC: efficiency, heat, ageing and price 3. What it means when you buy 4. What this comparison cannot tell you Figures and denominatorsRelated readingReferences **In short:** TOPCon changes the part of a PERC cell that limits it most, the metal contacts at the back, so on paper it should be more efficient and lose less in the heat. TOPCon modules in our catalogue state a median efficiency of 22.5 % and a temperature coefficient of -0.29 %/°C, PERC modules 20.7 % and -0.35 %/°C. Matched Polish offers have medians of 0.142 EUR/W for TOPCon and 0.189 EUR/W for PERC, and I'd buy PERC only where it's clearly cheaper per watt and the roof has room to spare. PERC carried the market for years and TOPCon is its successor. Shops sell them side by side, and the datasheets look alike. Four differences cost or save you money: power per square metre, the share of it heat takes, the ageing the warranty allows, and price per watt. PERC is the baseline throughout; here is one of its cells from both sides. ![Front and rear of a monocrystalline PERC solar cell side by side, blue front with busbars and fingers, pale rear](https://comparepv.com/static/images/articles/topcon-perc-cell-front-and-back.webp) *Front (left) and rear (right) of a PERC silicon cell, the type most TOPCon modules are compared against. Image: WhistlingBird, [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0).* ### How the two groups were built Our catalogue lists 5,733 modules as TOPCon and 4,306 as PERC. Another 1,656 say only "N-type" without naming the cell structure. Some of those may be TOPCon, but the datasheet doesn't say so, so I left them out of both groups. Every catalogue figure here is what a manufacturer printed on a datasheet: a rating referenced to standard test conditions or a warranty term. None of it is our own measurement. The [datasheet guide](https://comparepv.com/articles/how-to-read-a-solar-panel-datasheet) explains where each figure sits on the sheet. Group medians have two traps. Each group mixes manufacturers in different proportions, and TOPCon is the newer technology, so its datasheets describe newer designs. That's why, next to the medians, I compare each manufacturer that lists both technologies with itself. Prices come from the shop offers our crawler holds now. In Poland it holds 1,171 offers for single rooftop modules, and the matcher tied 351 of them to a catalogue module by part number. Only that tie tells us the cell, because a shop title rarely names it. The sanity ranges and the count behind each figure are in Figures and denominators, under the article. #### The two example modules Two modules carry the worked examples, picked by rule when I wrote this: the PERC and the TOPCon module with the most shop offers on their [ComparePV pages](https://comparepv.com/offers), ties broken alphabetically. Both come from the same manufacturer, which keeps the brand out of the comparison. Nobody paid for a place. The PERC example: Scorecard for this module: [open its page on ComparePV](https://comparepv.com/panel/ja-solar-jam60s20-380-mr-1). The TOPCon example: Scorecard for this module: [open its page on ComparePV](https://comparepv.com/panel/ja-solar-jam54d40-460-lb-1). ### TOPCon vs PERC: efficiency, heat, ageing and price #### What is different inside the cell The difference sits at the back of the cell, where the metal contacts meet the silicon. Feldmann and colleagues at Fraunhofer ISE, introducing the tunnel oxide passivated contact in 2013, describe high-efficiency cells as "often limited by the recombination at the metal semiconductor contacts". Recombination is charge lost before it reaches the wire. A PERC cell still has metal touching silicon at every laser opening in its rear. TOPCon puts a thin oxide and a doped silicon layer between the two, the layer in the right-hand drawing below. ![Cross-section diagrams of three silicon cell designs, IBC, heterojunction and TOPCon, with labelled layers and metal fingers](https://comparepv.com/static/images/articles/topcon-cell-structure-designs.webp) *Cross-sections of three n-type silicon cell designs; the right-hand TOPCon drawing shows the thin oxide and polysilicon layer on the rear that separates it from PERC. Image: [IvanG-PV](https://commons.wikimedia.org/wiki/File:Advanced_silicon_cells.tif), [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0).* The figure below takes both cells apart layer by layer, with HJT as a third, and shows where the charge is lost. **Inside the cell: PERC, TOPCon and HJT** Switch between the three cells, select a layer to see what it does, and turn up the losses at the rear contact to see what happens to the voltage. Light enters a solar cell from the front and is absorbed in the silicon wafer, where it frees pairs of electrons and holes. Each carrier has to reach its own contact before it meets a carrier of the other kind and recombines; a recombined pair is current that never leaves the cell. A PERC cell covers the back of its wafer with a passivating layer, but a laser opens small holes in it so the aluminium behind can touch the silicon, and pairs are lost at every one of those openings. TOPCon puts a tunnel oxide a few atoms thick and a layer of doped poly-silicon over the whole back, so electrons pass and the metal never touches the wafer. HJT covers both faces with thin amorphous silicon and transparent conductors, so no metal touches the crystal at all. Fewer pairs lost means a higher open-circuit voltage, and a cell with a higher voltage loses a smaller share of its power per degree of heat. That is the order the three cells come in, PERC, then TOPCon, then HJT. Interactive on the web page. #### Efficiency and heat losses Module efficiency is the share of sunlight on the module's area that leaves it as power, so it decides how many watts fit on a roof. The temperature coefficient is the share of power lost per degree of cell temperature above 25 °C, so the figure closer to zero loses less on a hot roof. In the table, read the percentile row as well as the medians. | Figure | TOPCon | PERC | | --- | --- | --- | | Module efficiency, median | 22.5 % | 20.7 % | | Efficiency, 10th to 90th percentile | 21.5 to 23.3 % | 19.1 to 21.5 % | | Pmax temperature coefficient, median | -0.29 %/°C | -0.35 %/°C | Hold the 90th percentile of PERC against the 10th percentile of TOPCon. If the first sits below the second, nine in ten modules of each group fall on their own side of the line. If they cross, single datasheets matter more than the label. 77 % of TOPCon modules state an efficiency of 22 % or more, against 1 % of PERC modules. The two histograms share their efficiency bins. The groups differ in size, so compare the shapes rather than the bar heights. *Based on 5,733 modules with a stated value; the line marks the median, 22.5 %.* The numbers behind the chart | Module efficiency, TOPCon (%) | Modules | | --- | --- | | \<17 | 127 | | 17-18 | 13 | | 18-19 | 32 | | 19-20 | 28 | | 20-21 | 106 | | 21-22 | 1,036 | | 22-23 | 3,122 | | 23-24 | 1,170 | | 24+ | 99 | *Based on 4,306 modules with a stated value; the line marks the median, 20.7 %.* The numbers behind the chart | Module efficiency, PERC (%) | Modules | | --- | --- | | \<17 | 155 | | 17-18 | 110 | | 18-19 | 136 | | 19-20 | 504 | | 20-21 | 1,791 | | 21-22 | 1,569 | | 22-23 | 24 | | 23-24 | 17 | | 24+ | 0 | The [temperature coefficient article](https://comparepv.com/articles/cell-technology-temperature-coefficient) draws the same pair for heat losses, and the [hot climate article](https://comparepv.com/articles/panels-for-a-hot-climate) turns them into output in a hot hour. #### Warranted ageing The performance warranty, usually a linear power warranty, states how much power a module may lose and stay in spec. Lower allowances and a higher end power are the better promise. | Warranty figure | TOPCon | PERC | | --- | --- | --- | | First-year degradation allowance | 1.0 % | 2.0 % | | Annual degradation allowance | 0.40 %/yr | 0.55 %/yr | | Performance warranty of 30 years or more | 91 % | 42 % | | Power promised at warranty end | 87.4 % | 84.8 % | There's a physical reason the first year can differ. The UNSW PV Manufacturing course names "the metastable boron-oxygen (BO) defect formation" as "the primary source" of carrier-induced degradation in boron-doped p-type wafers, a common base for PERC cells, and notes that gallium doping avoids it. TOPCon is usually built on n-type wafers. The glossary entry on LID and LeTID covers both losses. So where a TOPCon datasheet allows less for the first year, there is a cause behind it, though the allowance itself is a term the manufacturer chose. #### The same manufacturer, both technologies 91 manufacturers list modules of both technologies, and comparing each with itself takes the brand out of the difference. Each row counts the manufacturers where TOPCon came out better, out of those that state the figure on both sides. | Figure | TOPCon better | Manufacturers compared | | --- | --- | --- | | Efficiency, higher median | 89 | 91 | | Temperature coefficient, less loss per degree | 85 | 91 | | Annual degradation allowance, lower | 71 | 77 | The closer the first column comes to the second, the more the gap holds inside each brand. A first column near half the second would mean the medians above mostly reflect which brands sit in each group. Product warranties split three ways: 50 manufacturers give both technologies the same median product warranty, 26 a longer one for TOPCon and 12 a shorter one. The [warranty article](https://comparepv.com/articles/product-warranty-vs-performance-warranty) explains what that term covers. #### What they cost The table gives euro per watt before tax for matched Polish offers. I kept prices to Poland because it held the most matched offers when I wrote this; the [price per watt article](https://comparepv.com/articles/solar-panel-price-per-watt-by-market) covers every market. Read the middle half as well as the median, and check the offer and shop counts: a group resting on a few shops can see its median move with one price list. | Group | Median (EUR/W) | Middle half (EUR/W) | Offers | Shops | | --- | --- | --- | --- | --- | | TOPCon | 0.142 | 0.130 to 0.154 | 160 | 23 | | PERC | 0.189 | 0.143 to 0.249 | 36 | 11 | The offers cover 86 TOPCon and 28 PERC catalogue modules. Where the two middle halves don't overlap, three in four offers of one group are cheaper than three in four of the other. This is what a buyer meets in Polish shops; it says nothing about what either cell costs to make. These are the cheapest current offers for the TOPCon example, each in the shop's own currency and on the side of VAT the shop printed: Cheapest current offers for [JA Solar JAM54D40-460/LB](https://comparepv.com/panel/ja-solar-jam54d40-460-lb-1), prices read 9 Oct 2026. | Shop | Market | Price | Availability | | --- | --- | --- | --- | | [Megawat Elektrohurt](https://comparepv.com/go/1839) | Poland | 321.03 zł incl. VAT | In stock | | [PV Zenit](https://comparepv.com/go/3208) | Poland | 333.00 zł incl. VAT | In stock | | [Eco System Projekt](https://comparepv.com/go/179) | Poland | 350.00 zł incl. VAT | In stock | *Each price is the figure the shop printed, on its own side of VAT.* ### What it means when you buy The arithmetic below uses the two example modules' datasheet figures, as our catalogue holds them. #### More power from the same roof The PERC module is rated 380 W on 1,769 by 1,052 mm, the TOPCon module 460 W on 1,762 by 1,134 mm. Divide the rating by the module area and you get power per square metre: - PERC: 380 W / (1.769 m × 1.052 m) = 380 / 1.861 = 204.2 W/m² - TOPCon: 460 W / (1.762 m × 1.134 m) = 460 / 1.998 = 230.2 W/m² On 20 m² of usable roof that is 20 × 204.2 = 4.08 kW against 20 × 230.2 = 4.60 kW. The TOPCon roof carries 12.7 % more from the same area. #### More of it left on a hot day Heat widens the gap. With the cells at 65 °C, 40 degrees above the rating condition, the PERC module at -0.35 %/°C keeps 1 - 0.0035 × 40 = 86.0 % of its rating. The TOPCon module at -0.29 %/°C keeps 1 - 0.0029 × 40 = 88.4 %. Per square metre that is 204.2 × 0.860 = 175.6 W against 230.2 × 0.884 = 203.5 W, now 15.9 % apart. The [heat yield comparison](https://comparepv.com/tools/heat-yield-comparison) runs the same sum for any two modules and any air temperature. Below it runs live, with a TOPCon median module as A and a PERC median module as B. **What a hot roof does to two modules** Set the air temperature and the sunlight, give two modules their datasheet figures, and watch the cells heat up and the output bars move apart. A module's rating is measured with its cells at 25 °C. In sunshine the cells run well above the air: with a NOCT of 45 °C, about 31 °C above it at 1000 W/m². Every degree above 25 °C costs the Pmax temperature coefficient, so at 30 °C air and full sun, for example, a 400 W module with -0.29 %/°C gives about 358 W, and one with -0.35 %/°C about 349 W. That gap of about 9 W, a little over 2 % of the rating, is what the coefficient is worth in the hottest hours. A lower NOCT helps the same way, by keeping the cells cooler. Interactive on the web page. #### What each warranty promises The PERC datasheet allows 2 % in the first year and 0.55 % a year after that, over 25 years: 100 - 2 - 0.55 × 24 = 84.8 % at year 25. The TOPCon datasheet allows 1 % and 0.40 % over 30 years: 100 - 1 - 0.40 × 24 = 89.4 % at year 25, and 100 - 1 - 0.40 × 29 = 87.4 % at year 30. That's what each manufacturer promises to make good, which is a different thing from how the module will age. #### Which one to buy If roof area limits the system, the efficiency gap is what you pay for. The [roof-fit selector](https://comparepv.com/tools/roof-fit-selector) shows how much it adds on your roof. If the roof has room to spare, price per watt decides. At an equal price the TOPCon example wins on area, heat and warranty, so a PERC offer has to be cheaper per watt to compete with it. I wouldn't pick PERC at an equal price. Where the two spreads overlap, a well-specified PERC module can beat a weak TOPCon one, so compare the two you're actually considering in the [panel comparison calculator](https://comparepv.com/tools/panel-comparison-calculator). ### What this comparison cannot tell you The counts are modules, not datasheets. One datasheet usually lists a ladder of power ratings, several sizes of the same module, and each rating is its own catalogue row, so a manufacturer with long ladders weighs more in every median. The worked examples assume power scales with area and temperature exactly as the coefficients say, and that warranty allowances run in a straight line. Real yield also depends on the inverter, shading and climate, none of which is in the sums. The price comparison covers one market, only the offers the matcher could tie to the catalogue, and only those live when the page is served. ## 01. Figures and denominators How the figures above were computed. Every figure is recomputed from the catalogue and the live shop offers when the page is served, and each one counts only the modules or offers that publish the value. Catalogue figures are computed from the modules listed in our catalogue (the rankings view, which keeps only modules with a power rating and a page): 14,005 modules. Each is a row read from its manufacturer's datasheet, and one datasheet usually covers a ladder of power ratings, so a datasheet with eight ratings is eight modules here. A module counts as TOPCon or PERC when its datasheet names that cell technology; modules labelled only "N-type" are left out of both groups. Each figure keeps only values in a sanity range: efficiency from 5 to 30 %, a Pmax temperature coefficient between -1 and 0 %/°C, annual degradation above 0 and below 2 % per year, a first-year allowance above 0 and below 5 %. A value outside the range is an extraction error, not a datasheet claim. The manufacturer comparison takes, for each manufacturer listing modules of both technologies, the median of each figure on each side, and counts a side only where it has a median. Prices come from the shop offers our crawler holds now, one row per product page, kept for a week after the crawler last saw them. An offer counts when it is a single module of 400 to 800 W with a price before tax between 0.05 and 2 EUR per watt, converted to euro at the day's ECB rate. The TOPCon and PERC price comparison uses only Polish offers that our matcher tied to one catalogue module by its part number, since a shop title rarely names the cell. | Figure | Value | Computed over | | --- | --- | --- | | TOPCon: module efficiency, median | 22.5 % | 5,733 modules | | PERC: module efficiency, median | 20.7 % | 4,306 modules | | TOPCon: modules in the catalogue | 5,733 | 14,005 modules | | PERC: modules in the catalogue | 4,306 | 14,005 modules | | N-type: modules in the catalogue | 1,656 | 14,005 modules | | Poland: offers matched to a catalogue module | 351 | 1,171 offers | | TOPCon: module efficiency, 10th percentile | 21.5 % | 5,733 modules | | TOPCon: module efficiency, 90th percentile | 23.3 % | 5,733 modules | | PERC: module efficiency, 10th percentile | 19.1 % | 4,306 modules | | PERC: module efficiency, 90th percentile | 21.5 % | 4,306 modules | | TOPCon: share with a module efficiency of 22 % or more | 77 % | 5,733 modules | | PERC: share with a module efficiency of 22 % or more | 1 % | 4,306 modules | | TOPCon: first-year degradation allowance, median | 1.0 % | 4,889 modules | | PERC: first-year degradation allowance, median | 2.0 % | 3,459 modules | | TOPCon: annual degradation, median | 0.40 %/yr | 4,937 modules | | PERC: annual degradation, median | 0.55 %/yr | 3,356 modules | | TOPCon: share with a performance warranty of 30 years or more | 91 % | 5,727 modules | | PERC: share with a performance warranty of 30 years or more | 42 % | 4,263 modules | | TOPCon: power at the end of the performance warranty, median | 87.4 % | 5,213 modules | | PERC: power at the end of the performance warranty, median | 84.8 % | 3,706 modules | | Manufacturers listing both TOPCon and PERC modules | 91 | 91 manufacturers | | Manufacturers of both whose TOPCon median efficiency is higher than PERC | 89 | 91 manufacturers | | Manufacturers of both stating efficiency on both sides | 91 | 91 manufacturers | | Manufacturers of both whose TOPCon median Pmax coefficient is smaller in size than PERC | 85 | 91 manufacturers | | Manufacturers of both stating a Pmax coefficient on both sides | 91 | 91 manufacturers | | Manufacturers of both whose TOPCon median annual degradation is lower than PERC | 71 | 91 manufacturers | | Manufacturers of both stating annual degradation on both sides | 77 | 91 manufacturers | | Manufacturers of both whose TOPCon and PERC median product warranties are equal | 50 | 88 manufacturers | | Manufacturers of both whose TOPCon median product warranty is longer than PERC | 26 | 88 manufacturers | | Manufacturers of both whose TOPCon median product warranty is shorter than PERC | 12 | 88 manufacturers | | Modules in the catalogue | 14,005 | 14,005 modules | ## 02. Related tools [Heat yield comparison](https://comparepv.com/tools/heat-yield-comparison) [Roof-fit selector](https://comparepv.com/tools/roof-fit-selector) [Panel comparison calculator](https://comparepv.com/tools/panel-comparison-calculator) ## 03. Related reading #### Cell technology and the temperature coefficient [Open](https://comparepv.com/articles/cell-technology-temperature-coefficient) Datasheet temperature coefficients grouped by cell technology across our catalogue, with medians, spreads and what the gap is worth on a hot roof. #### Solar panel price per watt by market [Open](https://comparepv.com/articles/solar-panel-price-per-watt-by-market) What a rooftop solar module costs per watt before tax in each market, from live shop offers, with the spread inside each country and what it means for a buyer. ## 04. Reference list 1. [Feldmann et al., A passivated rear contact for high-efficiency n-type silicon solar cells enabling high Vocs and FF>82%, Fraunhofer ISE, 28th EU PVSEC, 2013](https://www.ise.fraunhofer.de/content/dam/ise/de/documents/publications/conference-paper/28-eupvsec-2013/Feldmann.pdf) 2. [PV Manufacturing Education, PERC solar cells (UNSW)](https://www.pv-manufacturing.org/solar-cells/perc/) 3. [PV Manufacturing (UNSW), Carrier induced recombination](https://pv-manufacturing.org/lid-cid/) --- Source: https://comparepv.com/articles/topcon-or-perc