Watt: Solar for Van & RV

Pay once. No subscription, no ads, no account. Works offline.

Watt is the iOS solar sizing assistant for DIY van conversions, RVs, off-grid cabins, and tiny homes. Enter the appliances on board, pick your gear, and Watt computes the exact battery bank, panel array, MPPT controller, inverter, wire AWG, and fuse rating you need — with cited sources at every step.

Try every feature free for 2 days. Then unlock for good with a one-time purchase.

Features
• Daily energy audit — Σ(W × h) across appliances, AC loads divided by inverter efficiency
• Battery bank sizing — required usable Ah for your autonomy goal, chemistry-aware safe depth-of-discharge (LFP, AGM, flooded, gel)
• Solar array sizing — required panel wattage from US state-level NREL PVWatts peak sun hours
• MPPT controller sizing — output current with NEC 690.8 ×1.25 safety multiplier
• Cold-Voc check — warns when worst-case Voc lands within 10% of your controller's max input (the failure mode that kills MPPT controllers)
• Inverter sizing — continuous wattage with 1.1× safety on simultaneous AC load
• Wire AWG selection — NEC 2023 Table 310.16 ampacity sized to keep round-trip voltage drop ≤ 3% per NEC 210.19 Note 4
• Recommended fuse — 1.25× continuous current rounded to standard sizes per NEC 210.20
• Brand-cited gear picks — Renogy, Battle Born, Victron, Ampere Time, Redodo, Eco-Worthy, Bluetti, EcoFlow, Goal Zero, Rich Solar, BougeRV, Sunpower, Newpowa, HQST, Outback, EPEVER
• 92 cited appliance templates — from MaxxFan and 12V fridges to Starlink, e-bike chargers, and induction cooktops
• Universal app for iPhone and iPad

For van life — sprinter and promaster DIY conversions are the lead audience — plus RV upgraders, off-grid cabin builders, and tiny home setups.

$6.99 one-time after the 2-day trial. No subscription, no ads, no account, no cloud.

Educational guidance: Watt presents brand-cited sizing for educational purposes. Consult a licensed electrician for code-compliant installation, especially wire and fuse sizes.

Privacy: Watt collects nothing. No analytics, no accounts, no network requests. Your rig setup lives on your device.