Nice
Surprisingly useful for the price
Free
In-App Purchases
About
This app assists with solar system design for off-grid living and vehicle conversions. It calculates required battery banks, solar panels, controllers, inverters, and wiring sizes based on your appliances and gear. Offers cited sources and brand recommendations for components.
✓Solar system sizing calculations
✓Battery bank and panel array estimation
✓MPPT controller and inverter sizing
✓Wire AWG and fuse rating recommendations
✓Appliance and gear selection
✓Cited sources and brand recommendations
✓Offline functionality
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What's New in Watt
1.1
July 16, 2026
The number keyboard now has a Done button, so you can dismiss it when you're finished. Thanks to everyone who wrote in about this.
1
In-App Purchases
$6.99
Watt Pro (lifetime)
Full library, wire sizing, multi-rig, zip-PSH.
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FAQ
What is Watt used for?
Watt is an iOS solar sizing assistant designed for DIY van conversions, RVs, off-grid cabins, and tiny homes. It helps users calculate the necessary components for their solar power systems, including battery banks, solar arrays, controllers, and inverters.
Does Watt have a subscription?
No, Watt operates on a pay-once model. After a 2-day free trial, you can unlock all features permanently with a one-time purchase. There are no ongoing subscriptions, ads, or accounts required.
Can I use Watt offline?
Yes, Watt is designed to work offline. This means you can access all its features and perform calculations without needing an internet connection, making it ideal for remote locations or during van conversions.
What kind of appliances can I input into Watt?
Watt includes 92 cited appliance templates, covering a wide range of devices commonly used in off-grid setups. This includes items like MaxxFans, 12V refrigerators, Starlink systems, e-bike chargers, and induction cooktops.
Does Watt provide specific brand recommendations?
Yes, Watt offers brand-cited gear picks for various components. It lists popular brands such as Renogy, Battle Born, Victron, and EcoFlow, among others, to help users select compatible equipment.
What is the pricing for Watt?
Watt is free to download and use for a 2-day trial period. After the trial, a one-time purchase of $6.99 is required to unlock all features permanently. There are no subscriptions or ads.
Is Watt suitable for beginners?
Watt provides educational guidance and cited sources for its calculations, making it a valuable tool for beginners. However, for code-compliant installation, especially for wiring and fuse sizes, consulting a licensed electrician is recommended.
What devices does Watt support?
Watt is a universal app that supports both iPhone and iPad devices. This allows users to access the solar sizing assistant on their preferred Apple mobile device.