OffGridCalc — Free Off-Grid Solar & Battery Sizing Calculator
OffGridCalc is the most accurate, private, and completely free solar panel and battery sizing calculator available online. 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 professional-grade calculations in seconds — no account, no email, no subscription required. Ever.
What Is OffGridCalc?
OffGridCalc is a free web-based tool that helps homeowners, engineers, campers, and off-grid enthusiasts calculate exactly how many solar panels and how much battery storage they need to power their home or system independently from the utility grid. Unlike generic solar calculators, OffGridCalc uses real solar irradiance data from the PVGIS EU Science Hub database and precise location-based sun hour calculations to give you results tailored to your exact geographic location anywhere in the world.
Every calculation is performed entirely inside your browser. Your data never leaves your device. No personal information is stored, transmitted, or sold. OffGridCalc is 100% private by design.
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.
Completely Free, Forever
OffGridCalc is and will always be free. No freemium tiers, no locked features, no upsells. We believe solar energy education should be accessible to everyone regardless of income or location. Our operating costs are supported by non-intrusive advertising, not by charging users.
100% Private — Works Offline
Your energy data is sensitive. OffGridCalc never sends your calculation inputs to any server. All math runs locally in your browser using JavaScript. Once the page loads, the calculator works completely 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 accurate, localized results whether you are in Arizona, Germany, Nigeria, Australia, or anywhere else on the planet.
Who Uses OffGridCalc?
OffGridCalc is used by a wide range of people with different energy independence goals:
- Homeowners evaluating residential solar installation and considering going fully off-grid
- RV and van life enthusiasts sizing solar systems for mobile living
- Cabin and tiny home owners in remote locations without grid access
- Solar installers and engineers who need a quick professional estimation tool
- Students and researchers studying renewable energy systems
- Families in developing regions planning affordable solar access for the first time
- 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 highly accurate estimates based on real PVGIS solar irradiance data and industry-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.