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Watt: Solar Calculator for Van & RV — Support

Need help?

Email roman.kopaliani@gmail.com with your question. Please include:

Common questions

How does the 2-day free trial work?

The 48-hour clock starts the moment you finish onboarding. Until it runs out, every feature is unlocked — the full appliance library, every brand, wire and fuse sizing, multi-rig, all of it. When the trial ends, you'll see the Watt Pro paywall and can unlock everything for good with a one-time purchase. Your saved rig data stays put either way.

What happens to my rig when the trial expires?

Everything you entered is preserved on your device. After you purchase Watt Pro, the app picks up exactly where you left off.

I already bought Watt Pro on another device. How do I restore?

On the new device, open Settings → Restore purchases (or tap "Restore purchases" on the paywall). Your unlock will be restored from the App Store account that originally purchased.

The recommended wire AWG seems heavy. Why?

Watt sizes wire to keep round-trip voltage drop at or below 3% per NEC 210.19(A)(1) Informational Note 4, on top of NEC 2023 Table 310.16 ampacity at 75°C terminations. On long DC runs the voltage-drop budget tends to drive the AWG larger than ampacity alone would require — that's expected. For an installation review, consult a licensed electrician familiar with your local code.

The Voc cold-derate warning showed up. What does it mean?

Photovoltaic panel open-circuit voltage (Voc) rises as temperature drops. If your worst-case cold Voc lands within 10% of the controller's max input voltage, Watt warns you because real-world cold-weather conditions can push past the controller's max and damage it. The usual fix is fewer panels in series, or a controller with a higher max PV voltage rating. Cite from the Victron MPPT user manual worked examples.

My panel / battery brand isn't listed.

Watt ships brand-cited presets for the most common van and off-grid gear (Renogy, Battle Born, Victron, Ampere Time, Redodo, Eco-Worthy, Bluetti, EcoFlow, Goal Zero, Rich Solar, BougeRV, Sunpower, Newpowa, HQST, Outback, EPEVER). If your brand isn't represented, pick "Use generic defaults" at the top of each category — the math falls back to conservative generic values. If you'd like a specific brand added, send a note with a link to the manufacturer's spec sheet.

Should I trust this app for my exact build?

Watt provides brand-cited sizing math as a guide. It is not a substitute for guidance from a licensed electrician. Electrical safety in DC systems is load-bearing — wrong wire AWG can start a fire. Always have a qualified installer review your plans before energizing anything.

Does the app work offline?

Yes — Watt never makes general network requests. The only exception is Apple's StoreKit, which is contacted to fetch the Watt Pro price and to restore purchases. The sizing math itself is all local.

How do I delete my data?

Delete the app from your iPhone or iPad. All local data is removed along with it.

Safety reminder

DC electrical systems carry real risk. A wrong wire AWG, an undersized fuse, a panel string that runs above the controller's max PV input on a cold morning — any of these can start a fire or damage a $300 controller. Watt presents brand-cited sizing for educational purposes. Consult a licensed electrician for code-compliant installation, especially for wire and fuse sizes. When in doubt, oversize the wire and fuse the source side properly.