Off-Grid Calculator Suite

About This Tool

The Off-Grid Calculator Suite provides three essential tools for anyone planning or maintaining an off-grid power system. The Wire Gauge Calculator helps you select the correct wire size based on current, voltage, and distance to minimize voltage drop and prevent overheating. The Solar ROI Calculator estimates payback periods and long-term savings using regional solar irradiance data, installation costs, and local electricity rates. The Battery Runtime Predictor tells you how long a specific appliance will run on a given battery capacity, accounting for depth of discharge and inverter efficiency.

Whether you are building a van conversion, a remote cabin, or an emergency backup system, these calculators help you make informed decisions without expensive software. The regional solar data is sourced from NASA's POWER database, providing realistic peak sun hour estimates for locations worldwide. All calculations include safety margins (NEC recommended 80% derating for continuous loads) and real-world efficiency factors to ensure your system design is both safe and practical.

Common Use Cases

• Planning wire sizes for solar panel installations, inverter connections, and battery banks
• Estimating solar panel return on investment before purchasing equipment
• Predicting battery runtime for off-grid appliances like fridges, lights, and water pumps
• Sizing battery banks for van life and RV conversions based on daily energy needs
• Comparing solar installation costs and payback periods across different regions
• Ensuring wire gauge compliance with electrical codes for safe off-grid installations

Pro Tips

• Always account for voltage drop when sizing wires — aim for less than 3% total drop from source to load
• Consider your region's peak sun hours when calculating solar ROI — the tool uses NASA data for accurate regional estimates
• Use 80% depth of discharge (DoD) for lithium batteries and 50% for lead-acid to maximize battery lifespan
• For DC circuits, always round up to the next available wire gauge to ensure a safety margin

Frequently Asked Questions

What wire gauge should I use for my solar panels?

The correct wire gauge depends on the current (amps), voltage, and distance between the panels and charge controller. Use the Wire Gauge Calculator to get a precise recommendation — input your system specifications and it will suggest the minimum safe wire size.

How accurate is the solar ROI calculation?

The Solar ROI Calculator uses regional peak sun hour data from NASA's POWER database, which provides reasonably accurate monthly averages. Actual results may vary due to weather patterns, panel orientation, shading, and seasonal variations. The estimates are best used for comparison and initial planning.

What depth of discharge should I use for my batteries?

Lithium batteries can typically handle 80-100% DoD without significant degradation, while lead-acid batteries should be limited to 50% DoD to maximize cycle life. The Battery Runtime Calculator uses 80% DoD and 95% inverter efficiency by default.

Can I use these calculators for grid-tied systems?

Wire gauge calculations apply to any electrical installation. The solar ROI estimator is primarily designed for off-grid systems. For grid-tied systems, additional factors like net metering policies and feed-in tariffs significantly affect ROI.

Part of the FreeQ.One tools suite.