OffGridCalc — Free Off-Grid Solar & Battery Sizing Calculator
OffGridCalc is an advanced, private, and completely free solar panel and battery sizing calculator. Whether you are planning a full off-grid home, a cabin retreat, an RV solar system, or an emergency backup power setup, OffGridCalc gives you accurate location-based estimates in seconds — no account, no email, no subscription required.
What Is OffGridCalc?
OffGridCalc is a free web-based tool that helps homeowners, engineers, campers, and off-grid enthusiasts calculate solar panel and battery storage requirements to power their system independently from the utility grid. OffGridCalc uses real solar irradiance data from the PVGIS EU Science Hub database and location-based sun hour calculations to give you reliable estimates tailored to your geographic location.
Every calculation is performed entirely inside your browser. Your calculator inputs never leave your device — we don't transmit or store what you calculate. Like most sites, we use standard analytics and cookies to improve performance — see our Privacy Policy for details.
How the Solar Calculator Works
Getting your solar system estimate takes less than two minutes. Simply enter your location, tell us about your home size and the appliances you want to power, choose your desired battery autonomy (how many days of backup power you want), and select your solar panel efficiency rating. OffGridCalc instantly calculates:
- Total daily energy consumption in watt-hours based on your appliances and usage patterns
- Required solar panel capacity in kilowatts, accounting for real sun hours at your location and system losses
- Battery bank size in kilowatt-hours, sized for your chosen autonomy days and depth of discharge
- Estimated system cost based on current average equipment prices
- Estimated annual savings compared to your local grid electricity rates
- Payback period so you can understand the financial return on your investment
Why Choose OffGridCalc?
Accurate Real-World Data
Most solar calculators use rough average figures that may be completely wrong for your location. OffGridCalc pulls actual solar irradiance data for your city from PVGIS, the same database used by professional solar engineers in Europe and worldwide. This means your results reflect real sun hours for your specific latitude, climate, and season — not a generic national average.
Free to Use — No Registration
OffGridCalc is free to use with no account or subscription required. No locked features, no hidden tiers. We believe solar energy planning tools should be accessible to everyone.
Private Calculator Inputs — Offline Support
Your energy data is sensitive. OffGridCalc never sends your calculation inputs to any server. All math runs locally in your browser using JavaScript. After the calculator and required location data are loaded, supported calculations can continue offline — ideal for remote site visits, areas with poor mobile data, or anyone who values privacy.
Global Coverage
OffGridCalc supports any location in the world. Enter any city, town, or region and our calculator will retrieve the correct solar irradiance data and local electricity pricing to give you location-based estimates whether you are in Arizona, Germany, Nigeria, Australia, or anywhere else on the planet.
Who Uses OffGridCalc?
OffGridCalc is designed for anyone planning energy independence:
- Homeowners evaluating residential solar options and battery backup capacity
- RV and van life enthusiasts sizing solar systems for mobile living
- Cabin and tiny home owners in remote locations without grid access
- Solar enthusiasts and DIY designers who need a quick preliminary estimation tool
- Students and educators studying renewable energy systems
- Emergency preparedness planners designing backup power systems
Frequently Asked Questions
Is OffGridCalc really free?
Yes. OffGridCalc is completely free with no hidden costs, no registration, and no trial periods. All features are available to all users at all times.
How accurate are the results?
Our results are estimates based on real PVGIS solar irradiance data and standard sizing algorithms. They provide an excellent starting point for planning your system. For final installation decisions, we recommend consulting a certified solar professional who can assess your specific site conditions.
Does OffGridCalc store my data?
No. All calculations happen entirely in your browser. We do not store, collect, or transmit any of your calculator inputs. Your information stays on your device.
Can I use it on my phone?
Yes. OffGridCalc is fully responsive and works on all devices including smartphones and tablets. It is also a Progressive Web App (PWA) that you can install on your home screen for quick offline access.
Start Calculating Your Energy Independence
Ready to find out how many solar panels you need? Use our free calculator now and get your personalized solar system recommendation in under two minutes.
Open the Solar Calculator →
Have questions? Visit our Solar Energy Blog for guides, tips, and in-depth articles, or contact us directly. Learn more about OffGridCalc and our mission to make energy independence accessible to everyone.