Off-Grid Solar System Calculator

An off-grid solar system runs entirely on solar power with no utility connection, requiring careful sizing to avoid running out of energy. Enter your zip code, daily energy usage, peak load, battery type, days of battery backup, and system voltage into the Off-Grid Solar System Calculator to find your recommended solar panel array size. Secondary outputs include battery bank capacity, inverter size, peak sun hours for your location, and an estimated system cost.

Used to determine peak sun hours in your area

kWh

Total kilowatt-hours used per day

watts

Maximum power needed at one time

days

Number of cloudy days to power your home

%

Typical range is 85-95%

Results

Solar Panel Array Size

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Battery Bank Capacity

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Battery Bank (Amp Hours)

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Inverter Size

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Peak Sun Hours

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Estimated System Cost

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Frequently Asked Questions

How many sun hours a day do you average in the darkest month?

Peak sun hours vary by location and season. Most areas in the US receive 3-7 peak sun hours per day, with winter months typically having 2-4 hours. Our calculator uses your zip code to estimate this automatically.

What's the difference between lead acid and lithium batteries for off-grid systems?

Lithium batteries can be discharged to 80% depth while lead acid should only be discharged to 50%. Lithium batteries also last longer (10+ years vs 3-5 years) but cost more upfront.

How do I calculate my daily energy usage?

List all your appliances with their wattage and daily usage hours. Multiply watts × hours for each appliance, then sum everything up. For example: 100W light × 5 hours = 500Wh per day.

What size inverter do I need for my off-grid system?

Your inverter should be sized 20-25% larger than your peak load to handle surge currents and provide safety margin. Pure sine wave inverters are recommended for sensitive electronics.

How many days of battery backup should I plan for?

Most off-grid systems are designed for 3-5 days of autonomy without sun. Areas with frequent cloudy weather may need 5-7 days, while sunny climates might only need 2-3 days.

Can I expand my off-grid solar system later?

Yes, but it's easier to plan for future expansion from the start. Make sure your charge controller and inverter can handle additional panels, and design your battery bank for easy expansion.

What's the typical lifespan of an off-grid solar system?

Solar panels last 25+ years, inverters 10-15 years, lithium batteries 10-15 years, and lead acid batteries 3-7 years. Proper maintenance extends all component lifespans.

How much does a complete off-grid solar system cost?

Costs range from $15,000-$50,000+ depending on system size and components. Expect $3-8 per watt for the complete system including installation, with lithium systems costing more upfront but offering better long-term value.