SunStem: Solar Calculator

Size solar, battery, MPPT, wire and fuse offline. Forecast runtime, audit seven days and leave with a clear next action.

SunStem is an offline solar and battery calculator for RVs, vans, boats and cabins. Build a saved system profile, then estimate battery runtime, solar yield, reserve risk and safer system sizing on iPhone or iPad.

CALCULATE BATTERY RUNTIME

• Compare load, solar and usable battery capacity
• Forecast the next charge window and hours to the reserve floor
• Work offline from a saved profile and local inputs

SIZE AN OFF-GRID SYSTEM

• Review battery, PV, MPPT, inverter, wire and fuse planning outputs
• Check voltage drop, cold Voc and fuse-versus-wire safety gates
• See assumptions and deterministic calculations from the native core

AUDIT THE NEXT SEVEN DAYS

• Scan daily reserve risk from saved load and solar assumptions
• See what to shed, when to charge and why the risk changed
• Export facts for a trip partner, installer or hardware review

No cloud account is required before first value. SunStem provides planning estimates and field-review evidence, not engineering certification. It does not control chargers, inverters or BMS hardware. Background or unattended hardware monitoring is not promised in this release.