How Many Solar Panels for a 5kW System? (2026 Guide)

How many panels does a 5 kW system need?

Most 5 kW (5,000 W) systems use 12–13 panels built from today's common 400–450 W modules — exactly 13 at 400 W, 12 at 425 W or 450 W — or 10 panels of the newer 550 W hardware. Since you can't install half a module, the real array always lands a little above 5,000 W: 13 × 400 W = 5,200 W and 12 × 425 W = 5,100 W. Confirm your exact roof and bill with the solar panel calculator.

The count is simply 5,000 ÷ panel wattage, rounded up: at 400 W that's 5,000 ÷ 400 = 12.5 → 13 panels; at 425 W it's 11.76 → 12; at 450 W it's 11.1 → 12; and at 550 W it's 9.09 → 10. Here is the same math with the roof each layout needs, assuming standard ~5.5 × 3.25 ft modules (≈ 17.9 sq ft each):

The footprint is panels × 17.9 sq ft: 13 × 400 W ≈ 233 sq ft (call it 230–240), the two 12-panel arrays ≈ 215 sq ft (about 210–220), and 10 × 550 W ≈ 179 sq ft (about 175–185). Those numbers are the glass only — real roofs need extra clear deck around the array, covered below.

What a 5 kW system produces each month

Say your household uses 700 kWh a month. A 5 kW array in a 4.5-peak-sun-hour climate produces about 5,000 W × 4.5 h × 30 days × 0.8 = 540 kWh a month — roughly 77% of that bill. In a sunnier 5.5-hour region the same system makes about 660 kWh, close to the whole load. That mix — 12–13 panels, a moderate roof footprint, and output in the range of a typical home's use — is why 5 kW is such a common quote.

Keep the two numbers straight: panel count comes from 5,000 ÷ panel watts rounded up, while monthly output depends on your local peak sun hours. If you'd rather size from your own electric bill than from a fixed system size, start with how many solar panels do I need.

Roof space: will a 5 kW array fit?

Plan on roughly 240–330 sq ft of clear, unshaded roof. The modules themselves cover about 175–235 sq ft (see the table above), and installers add roughly a third more deck for edge setbacks, vent clearance, and a service path along the array. A single large plane of that size fits all four layouts comfortably; hip roofs and dormer-divided planes waste usable surface, so count only unbroken, unshaded sections.

Roof size usually tracks house size. If you're comparing by home rather than by kilowatt, see how many solar panels a 2,000 sq ft home needs — most such roofs carry a 5 kW array with room to grow.

Real-world factors that change your results

• Inverter sizing and clipping: Pair a 5 kW array with a roughly 5–6 kW inverter (a DC:AC ratio near 1.2:1) so a cool, sunny day's 5.2–5.5 kW peak rarely clips; a bigger inverter adds cost, not output.
• Roof orientation: South-facing planes at a 20–35° pitch deliver the rated numbers; east- or west-facing roofs typically produce 10–20% less, and shade from chimneys, vents or trees can drop whole strings.
• Net metering: With net metering, surplus daytime kWh bank against night use at retail rates; without it, export credits are lower and the 540–660 kWh monthly figure overstates what you'll save on the bill.
• Local permits: Almost every jurisdiction requires an electrical permit and AHJ approval before the system can be switched on — your installer handles it, but plan for the paperwork to add 2–8 weeks.

If part of the plan is staying powered when the grid goes down, a generator is sized off your loads, not your roof — check what size generator do I need before comparing costs.

Estimate your solar panel count →