GarageWatts

GarageWatts

Project Overview

GarageWatts is a home EV charging cost tracker that gives drivers an exact cost-per-mile figure based on their actual electricity rate — without guessing, without a $25/month subscription, and without relying on the manufacturer's app. It pairs with a Shelly Plug ($24.99) to automatically capture every charging session, then applies the user's real utility rate to calculate true cost per session and per mile.

Most EV owners have no idea what their car actually costs per mile to charge at home. Factory apps show kWh delivered but apply national average rates that can be off by 30–50%. GarageWatts closes that gap: plug in the Shelly, log an odometer reading once a week, and the dashboard does the rest — automatically.

The Problem

EV owners charging at home face a fundamental visibility problem: their electricity bill goes up, but there's no clean way to attribute a specific dollar amount to their vehicle. Factory apps from manufacturers like Tesla, Rivian, and GM apply national average electricity rates — figures that can be 30-50% off for users in high-rate states like California, New York, or Hawaii.

Third-party EV tracking apps exist but require manual session logging or rely on telematics data not available on all vehicles. The result is that most EV drivers are operating blind: they know they're saving money versus gas, but they can't quantify how much, and they can't optimize around time-of-use utility rates. No affordable, automatic, hardware-agnostic solution existed for home-charged EVs across all makes and models.

How It Works

1. Install a Shelly Plug US Gen4 ($24.99) into the 120V wall outlet used for L1 charging.
2. The plug reports kWh consumed, session start/end times, and live power draw directly to GarageWatts.
3. Log your odometer once a week (30 seconds) — or connect a Vgate iCar Pro 2S ($33.99) for fully automatic odometer capture.
4. GarageWatts applies your actual utility rate to each session and calculates cost-per-mile between consecutive odometer readings.
5. View a live dashboard with session history, monthly totals, and efficiency trends.