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Off-Grid Solar Panel Calculator

Size your standalone system — batteries, panels & independence

✓ Free estimate, no signup required

Going fully off-grid means your solar system must handle 100% of your electricity — with no utility backup. That changes the math significantly. You'll need enough panel capacity to fill your batteries even on cloudy days, and enough battery storage to carry you through nights and multi-day overcast stretches. Most off-grid households size their panels 20–40% larger than a grid-tied system would require, specifically to account for charging headroom.

Calculator pre-loaded with typical off-grid solar defaults — adjust for your actual usage

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Key Considerations for Off-Grid Solar

  • ✓Battery bank sizing is the critical variable — panels charge the bank, not appliances directly
  • ✓Oversize panels by 20–40% to maintain battery health and handle bad weather
  • ✓Energy efficiency first: LED lighting, efficient appliances, and low-draw habits reduce panel count dramatically
  • ✓Generator backup is common for winter or extended cloudy stretches
  • ✓Inverter/charger selection matters — you need AC power from DC batteries

Off-Grid Solar Solar — Frequently Asked Questions

How many solar panels do I need to go fully off-grid?▾
Most off-grid cabins and homes need 10–40 panels depending on consumption. A modest off-grid setup using 300–500 kWh/month typically requires 12–20 panels (4–8 kW) plus 20–40 kWh of battery storage. Use the calculator above with your realistic monthly usage and add 30% for battery charging overhead.
What size battery bank do I need for an off-grid solar system?▾
A common rule of thumb is 1–3 days of autonomy. If you use 30 kWh/day, you'd want 30–90 kWh of usable battery capacity. Lithium (LFP) batteries can use 80–90% of rated capacity; lead-acid only 50%. Most off-grid homes install 20–60 kWh of lithium storage paired with 6–15 kW of panels.
Can I use this calculator for off-grid sizing?▾
Yes — with one adjustment. The calculator estimates how many panels you need to produce your annual kWh. For off-grid, take the panel count result and add 25–40% extra panels to ensure your batteries charge fully even in suboptimal weather. Size batteries separately based on your daily usage and desired autonomy days.
What's the cost of a complete off-grid solar system?▾
Expect $20,000–$80,000+ for a full off-grid setup including panels, inverter/charger, battery bank, and installation. A small cabin system (3–5 kW, 10–20 kWh batteries) might cost $15,000–$30,000. A full-size off-grid home system (8–15 kW, 30–60 kWh) typically runs $40,000–$80,000. The 30% federal ITC applies to off-grid systems too.
Is off-grid solar worth it if I can get grid power?▾
Off-grid is usually justified when grid connection costs exceed $15,000–$25,000 (common in rural areas where utility lines must be extended), when energy independence is a priority, or for remote properties where grid power simply isn't available. For most suburban homes, a grid-tied or battery-backup system offers better ROI.

Solar Calculators by State

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Related Guides

→How Many Solar Panels Do I Need?→How Solar Panel Calculators Work→Off-Grid Solar System Guide→Main Solar Panel Calculator

Other Solar Use Cases

🚐RV & Camper Solar🏡Cabin Solar🌾Farm & Agricultural Solar⛵Boat & Marine Solar🏢Commercial Solar

Disclaimer: This is an estimate for planning purposes only. Actual solar system size, cost, production, and savings depend on site-specific conditions. This tool does not constitute financial, engineering, or tax advice. Always consult a licensed solar installer and tax professional before purchasing. Data sources: NREL PVWatts, EIA Residential Energy Survey, EPA eGRID.