Watts per square metre, watts per kilogram
Power density is rated power divided by the module's own footprint. It is efficiency expressed the way a roof survey needs it: the median module puts 218 Wp on every square metre it covers, and the best puts 252.
Watts per kilogram is the other constraint, and it points the other way. The median is 18.8 Wp/kg; the modules at the top of that list are usually thin, frameless or flexible, and they buy their weight advantage with efficiency. A tight roof and a weak roof want different panels.
What the distribution shows
Power density and module efficiency are the same measurement in different units - 200 Wp/m² is 20%, since standard test conditions are 1000 W/m². The distribution has the same shape for that reason, and the 2,186 modules at 230 Wp/m² or better sit above the same line the efficiency page draws at 23%. Fewer panels appear here than there: a module has to declare its dimensions to be measured this way.
Specific power spreads much wider than density: from 0.9 to 74.1 Wp/kg. The top of this distribution is glass-free and flexible construction, not better cells, which is why the two lists below share almost no panels.
Rated power says how much roof a module needs, not how well it uses it. Across the sample the cloud is almost flat: a 100 Wp module in the sample reaches 213 Wp/m² while a 745 Wp one reaches 240. Buying by wattage alone gets you a physically larger panel, not a better one.
The densest and the lightest
Two lists, because they answer different questions and almost never name the same module.
By manufacturer
On a roof with room for 22 m² of modules, the median panel gives you 4,850 Wp and the densest gives you 5,598 Wp: the same array area, 15% more output for no extra mounting and no extra roof.
Where the roof is large and the budget is not, none of this matters and the cheapest watt wins. Density is a constraint metric: it earns its keep when area, not money, is what runs out first.
Run the panel comparison calculatorHow these numbers are built
Every figure comes from a manufacturer datasheet ingested into the panel database. Nothing is modelled, estimated, or supplied by a brand outside its own published specification.
Aggregates recompute as new panels arrive. A panel that does not declare a value is left out of that average rather than filled in, so every figure here is backed by modules that actually publish it.
No paid placements, and no figure here reads which shops pay us a commission. Each power rating counts as the module it is. Bifacial datasheets that quote one module at several assumed rear-side gains are counted once, on their front-side rating.