Watt: Solar for Van & RV
Battery, panels, wire & fuse
Free · In‑App Purchases · Designed for iPad. Not verified for macOS.
Stop jumping between websites. Watt sizes your battery bank, panel array, MPPT, inverter — wire and fuse too. Brand-cited gear picks. Pay once. No subscription.
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.
The developer, Roman Kopaliani, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Roman Kopaliani
- Size
- 3 MB
- Category
- Utilities
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - iPad
Requires iPadOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- In-App Purchases
Yes
- Watt Pro (lifetime) $6.99
- Copyright
- © 2026 Roman Kopaliani