The simple math — and the practical details
Panel count is system watts ÷ panel watts, always rounded up. A 7 kW system with 585 W panels needs 12 panels. But the practical part matters more: panels must fit your roof with room for airflow and cleaning access, and strings must match your inverter's voltage windows.
Choosing panel wattage
In 2026 the sweet spot for home installs is 585–610 W N-type panels. Bigger panels mean fewer mounts and connections, but they are heavier to handle on stairs and small roofs. If your roof is tight, high-efficiency panels (22%+) deliver more power per square foot.
How many solar panels do I need?
Divide your system size in watts by the panel wattage and round up. A 5 kW system needs 9 of today's common 585 W panels (8.55 exact); a 10 kW system needs 18. Enter your size above for the exact count, or start from your monthly units in the system size calculator if you do not know your kW yet.
How many solar panels can I fit on my roof?
Roughly one 585 W panel per 28 ft² once you allow for spacing and walkways — so about 18 panels on 500 ft² of clear roof, or a 10.5 kW array. Enter your roof area above to see the number for your space. Remember to measure only the shade-free, unobstructed area, not the whole roof.
How many solar panels do I need for a house?
Most homes land between 6 and 20 panels depending on the bill. A house with no daytime air conditioning often needs 6–10; one running ACs in the day needs 15–20. The honest way to size it is from your actual monthly units, not a rule of thumb.
Do more efficient panels produce more energy?
Per square metre, yes — efficiency matters most when roof space is tight. For the same kW rating, total output is similar; you simply need fewer square feet with high-efficiency panels.
How much roof space does one solar panel take?
A modern 585 W panel is roughly 21.6 ft² of glass; with spacing and maintenance walkways, plan 60–70 ft² of roof per kW installed.