Solar EV Charging: How to Charge Your Car for Free

Solar EV charging uses your rooftop solar panels to charge your EV instead of (or in addition to) grid electricity. There are three approaches, from simplest to most sophisticated:

1. Timer-based charging: Set your charger to run during peak solar hours (10am-3pm). Your solar system generates power, and if your household consumption is low, most of the charger's draw comes from solar. Simple, free, and works with any charger.

2. Solar diversion (CT clamp): Chargers like the Zappi, Evnex E2, and ZJ Beny use a CT (current transformer) clamp on your meter to monitor real-time solar export. When your panels produce more than your home uses, the charger automatically ramps up to absorb the surplus. When a cloud passes or the kettle turns on, the charger reduces its draw. This maximises solar usage without overloading your circuit.

3. Direct inverter communication: The Fronius Wattpilot communicates directly with Fronius solar inverters over your home network. This is the most precise method, with zero lag between solar changes and charger response. The trade-off is that it only works with Fronius inverters.

A typical EV uses 15-20kWh per 100km. If you drive 40km per day (the Australian average), you need 6-8kWh of charging per day.

A 6.6kW solar system in Sydney generates about 25kWh per day on average. After household consumption (typically 10-15kWh during solar hours), you have 10-15kWh of surplus available for EV charging. This is more than enough for average daily driving.

A 10kW+ system provides even more surplus, allowing you to charge larger batteries or drive more kilometres on solar alone. If you already have solar and are adding an EV, your existing system likely produces enough surplus during the middle of the day.

If you are installing solar and an EV charger at the same time, ask your installer to size the solar system with EV charging in mind. Adding an extra 2-3kW of panels ($1,500-$2,500) specifically for EV charging is one of the best energy investments available.

Here is the annual cost comparison for 15,000km of driving:

With feed-in tariffs dropping to 3-8c/kWh in most states, every kWh you put into your EV battery (worth 16-30c) is 2-10x more valuable than exporting it to the grid. A solar diversion charger automates this decision.

Zappi ($1,800-$3,000): The gold standard. Three modes: Fast (full power from grid), Eco (solar + grid top-up), Eco+ (solar only, will not draw from grid). Works with any solar inverter via CT clamp. The Eco+ mode is unique, allowing you to charge entirely from solar even if it takes all day.

Evnex E2 ($999-$1,600): Best value solar charger. CT clamp monitors solar export and adjusts charging accordingly. OCPP 2.0.1 compliant. From $999 installed, it is half the price of a Zappi.

Fronius Wattpilot ($1,800-$2,800): Best for Fronius solar systems. Direct inverter communication means zero-lag solar tracking. Three modes: Next Trip, Eco, Solar-only. Premium pricing is justified only if you have a Fronius inverter.

ZJ Beny ($700-$1,200): Budget solar option. CT clamp solar integration at the lowest price point. Good enough for most solar homes.