Size your off-grid solar system
A free sizing tool for self-builders: from requirements to a final report, with calculations based on real PVGIS production data — not a quote, a solid starting point for your project.
How it works
Twelve steps in four stages, always editable as you go
The path is twelve steps, grouped into four stages. You can go back to any step and recalculate everything.
Requirements & arrays
Requirements, exposure, panels, strings: system type, orientation, tilt and shading for every surface you have available.
Battery, inverter, cables
Load profile, battery, inverter, cable sizing: full technical sizing — battery capacity, inverter rating, conductor cross-section.
Real production data
Production and balance: monthly/annual production estimates from PVGIS (European Commission) for your exact site.
Hardware & report
A downloadable summary with 3D renders of your arrays, ready to bring on site.
Start simplified, or unlock everything for free
Simplified
always free
The easiest way to get the hang of the tool: a system with one roof or area, estimated annual consumption. Guided step-by-step with an intro tour, so you never have to figure it out on your own. No account required.
Complete
every feature
For anyone with more than one surface (e.g. roof and carport together) or who wants to fine-tune every detail: this is where you find every feature of the tool, including the more advanced ones.
The latest features we've added
Included in the Complete plan, at no extra cost — even the newest ones.
latest release
Minimum row spacing
For ground-mounted arrays, the recommended minimum spacing to avoid winter self-shading, calculated from your site's real latitude.
Annual simulation
The autonomy stress test extended to all 12 months, not just the worst one — see how many months the battery would hold up a day of bad weather.
Total cost estimate
An order-of-magnitude hardware cost — panels, battery, inverter, cables — broken down line by line, right in the Summary.
My projects
Review, rename or delete your past projects — completed ones stay viewable and re-downloadable as a PDF.
Seasonal tilt
For ground-mounted arrays, the optimal tilt month by month, calculated from your site's real data.
Hourly production chart
The shape of production through the day, month by month and per array — useful for seeing when the system actually produces.
With Complete you get them all, including the ones still to come.
Free, unlimited projects, no extra cost on future features.
Feedback
Help us improve
Have you tried the tool? Let us know what worked and what didn't — feedback is only used to decide what to improve, never shown publicly.
Stays private — only we read it, never shown to other users.
Opens your email app with the message ready to go — no account needed.
Support
Questions or feedback? Write to latuaisola.support@gmail.com.
Free
Simplified and Complete are both free, always — no payment required, no account needed to use them. Anyone who purchased previously keeps their access unchanged.
Support the project
The tool stays free thanks to people who support it. If it was useful to you, a free donation helps keep it updated.
Pre-sizing tool
An indicative pre-sizing tool, not a certified electrical design. Always have your installation verified by a qualified electrician in line with REBT (Reglamento Electrotécnico de Baja Tensión) (generally harmonised with the IEC/CENELEC 60364 standard) before connecting anything.