A 10kW system can be 25 panels at 400W or 20 panels at 500W. The choice matters more than it might seem.
Fewer high-wattage panels: less roof space, higher cost per panel
Higher-wattage panels (often achieved through higher efficiency — see the efficiency calculator) let you hit a target system size with fewer physical panels, useful when roof space is genuinely limited. These panels typically cost more per watt than standard-efficiency options, a premium that makes the most sense when space, not budget, is the binding constraint.
More standard-wattage panels: more roof space needed, typically lower cost per watt
Standard-efficiency panels are usually less expensive per watt, making them the more cost-effective choice when roof space isn't a limiting factor. Use the roof size calculator to check whether your available space comfortably fits a standard-panel-count system before assuming you need premium panels.
Fewer panels can mean simpler installation and fewer failure points
All else equal, fewer physical panels means fewer roof penetrations, fewer individual connections, and a somewhat simpler installation — a modest secondary benefit beyond the primary space consideration.
More panels can mean better shading resilience with microinverters
If part of your roof has partial shading, more smaller panels paired with microinverters (see our microinverter comparison) can sometimes handle irregular roof shapes and shading patterns more flexibly than fewer large panels.
Frequently asked questions
Do higher-wattage panels always mean higher efficiency?
Often yes for panels of similar physical size, but not always — a larger panel can achieve higher wattage at standard efficiency, so check the actual efficiency percentage, not just wattage, when comparing options.
Is it ever worth mixing panel wattages on one roof?
It's uncommon and can add complexity to system design and monitoring — most installations use a single panel model throughout for simplicity, reserving mixed approaches for unusual roof configurations with genuinely different space constraints in different areas.