How many solar panels do I need for a house? 2026 guide

The most-Googled solar energy question is always the same: 'how many solar panels do I need for my house?'. Short answer: it depends. Long answer is here, with the formula installers use and a step-by-step numerical example.

The basic formula

To size a solar system you only need three inputs: your daily consumption (Wh), your location's peak sun hours (PSH), and your system losses (cabling, temperature, inverter).

“Panel power (W) = Daily consumption (Wh) ÷ Peak sun hours × Loss factor”

— NREL formula, adapted

Real example for an average US home

A typical American home consumes 28-32 kWh per day. Let's use 30,000 Wh. In Texas or Arizona average annual PSH is around 5.5 h. The standard loss factor is 1.3 (NREL's 0.77 derate inverted).

• 30,000 Wh ÷ 5.5 h × 1.3 = 7,090 W of panels
• Using 410 W panels: 7,090 ÷ 410 ≈ 18 panels
• For full off-grid you'll also need a ~30-40 kWh battery bank

What changes the math

1. Peak sun hours (PSH)

Phoenix gets 6.5 PSH; Seattle only 3.5. That means you need almost 90% more panels in the Pacific Northwest to produce the same energy. Check NREL's PVWatts for your exact coordinates.

2. Net metering vs. battery storage

If you export excess to the grid under net metering, you can size tighter. If you want full energy independence with batteries, size at least 20% above your average consumption for cloudy days.

3. Tilt and orientation

South-facing, tilt equal to your latitude. Every 10° of deviation from optimum costs 2-5% of annual production.

For specific cases see our size-by-area guides: 100 m² (≈1,075 sq ft) home, 200 m² (≈2,150 sq ft) home or small apartment.

Shortcut: our calculator