How Many Solar Panels Do I Need? Easy Calculator for California Homes

If you're considering solar in California, this is probably the first question you asked:

"How many solar panels do I actually need?"

Here's a straightforward answer — no jargon, no fluff.

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The Simple Formula

1. Find Your Annual kWh Usage (from your utility bill)
2. Divide by 1,500 = Estimated system size (kW)
3. Divide system size by 0.4 = Number of 400W panels

Example: 10,800 kWh ÷ 1,500 = 7.2 kW system = ~18 panels

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Quick Reference Chart

Annual Usage	System Size	Panels Needed
6,000 kWh	4.0 kW	~10 panels
9,000 kWh	6.0 kW	~15 panels
12,000 kWh	8.0 kW	~20 panels
15,000 kWh	10.0 kW	~25 panels
18,000 kWh	12.0 kW	~30 panels

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5 Things That Change Your Panel Count

1. Roof Direction — South-facing produces most
2. Shading — Trees and obstructions reduce output
3. Utility Rate Plan — Time-of-use matters
4. Future Plans — EVs, AC, additions
5. Your Goal — 100% offset or just reduce the bill?

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Final Thought

The "right" number of panels is the one that fits your life. Confirm with a real design based on your home, roof, and usage. 🌞🏠