Engineering calculator
Solar, battery and cable sizing
Build a practical off-grid power plan in four steps: list your devices, set your battery and sun conditions, then review the panel, inverter, MPPT and cable estimates.
1. Daily loads
Start with the appliances you expect to use off-grid.
2–3. Battery and solar conditions
4. Battery and inverter checks
Select your equipment when available. These checks compare the estimated DC demand with the battery discharge limit and inverter voltage, continuous and peak ratings.
5. Other charging sources
Add driving and campsite charging to avoid sizing the solar array for energy that another source already supplies.
6. Panel and MPPT compatibility
Use the values printed on your panel and controller datasheets. The calculator checks cold-weather panel voltage, parallel-array current and controller charge-current limits.
Your system estimate
Use these values as a planning range, then verify each component against its datasheet.
Daily energy
—Solar energy still required
—Battery capacity
—Solar array
—Recommended inverter class
—Battery-side current
—Battery cable ampacity guide
—Battery-side fuse guide
—MPPT controller class
—MPPT protection guide
—Configured panel array
—Estimated peak current
—Minimum cable by voltage drop
—Voltage drop
—Minimum
—Lowest viable planning point
Balanced
—Recommended everyday range
Expandable
—Extra weather and growth margin
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VanSpecs Off-Grid System Plan
Generated from the values entered in the calculator.
Planning estimate only. Verify manufacturer datasheets, cable ampacity, fuse ratings, temperature derating, BMS limits and local electrical requirements before installation.
Results are planning estimates, not a substitute for a qualified electrical design or the manufacturer’s installation instructions.