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Off-grid · Vanlife · RV · Marine

Know the demand.Plan the reserve.

Estimate battery capacity, DC load current and copper cable voltage drop with clearly stated assumptions. Use the results to prepare for a qualified installer’s review.

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Stone cabin with rooftop solar panels at dusk beside an alpine lake and snow-capped mountains
  • Transparent formulas
  • Explicit assumptions
  • Professional review required

Planning tool, not an installation specification. Estimates only. Conductor sizing and protection require qualified review.

01 / Calculator

Plan your system.

Planning tool, not an installation specification. Results are estimates, not NEC or ABYC certification. Cable ampacity, fuse coordination, fault current and equipment compatibility require a qualified installer’s review. Do not purchase, install or energize a system solely on these results.

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Understand the mathSee the formulas, inputs and assumptions behind the estimates.Build a safety checklistKey considerations before design and installation.Choose hardware carefullyUnderstand the criteria that influence component selection.

02 / Methodology

Clarity before capacity.Safety before selection.

Reserve energy is what your loads draw while nothing is charging. Nameplate capacity adds back usable depth of discharge and derating—so it is always larger.

Explore the methodology

03 / Safety

Estimates are the start, not the sign-off.

Battery & BMSConfirm the manufacturer’s discharge, surge and charge-temperature limits, and never bypass BMS protections.Conductors & protectionVoltage drop is not ampacity. Fuse current, DC voltage and interrupt ratings are separate properties.Professional installationResidential, RV and marine rules differ. A qualified installer must identify and apply them.

Read the full safety checklist →

04 / Resources

Learn from primary sources.

Start with manufacturer wiring guidance and the standards bodies behind residential and marine rules. Hardware recommendations are under review—none are shown until each product’s ratings and suitability are verified.

All resources and selection criteria →