Solar Diversion and EV Charging: How to Fuel Your Car for Free

Solar diversion is one of the most powerful features in home energy management: instead of exporting surplus solar electricity to the grid for 4p to 15p per kWh, your EV charger automatically detects the surplus and routes it into your car's battery instead.

How Solar Diversion Works

A solar diversion charger monitors surplus generation continuously through a clamp meter installed at your consumer unit. When surplus rises above a threshold (typically 1.4kW), the charger begins drawing from that surplus and routing it into the vehicle. As surplus fluctuates, the charger modulates its power draw in real time to track available surplus without touching grid electricity.

In "Eco+" mode on the Zappi, the charger only draws from solar surplus. In "Eco" mode it prioritises solar but tops up from the grid to maintain a minimum charge rate.

How Much Free Mileage Can You Get?

A 4kWp solar system in Yorkshire on a clear summer day generates 20 to 30kWh. After daily household consumption of 8 to 10kWh, 10 to 22kWh is available for diversion.

At a typical EV efficiency of 3.5 to 4 miles per kWh: - 10kWh diverted: 35 to 40 miles of free driving per day - 22kWh diverted: 77 to 88 miles of free driving per day

Which Charger Should You Use?

Zappi (myenergi): The market leader for solar diversion. Specifically designed for this use case. Works with all solar inverter types via CT clamps with no software integration required. Available in 7kW single-phase and 22kW three-phase versions.

Ohme Home Pro: Offers solar awareness alongside Octopus Intelligent integration, but less elegant for pure solar-first diversion than Zappi.

Hypervolt: Basic solar diversion via third-party monitoring integration. Less seamless than Zappi.

Easee: Does not currently offer native solar diversion. Best suited to load-sharing setups.

For most homes with solar panels, the Zappi is the clear recommendation.

Does Battery Storage Affect Solar Diversion?

The battery typically takes priority for absorbing solar surplus. Once full, surplus flows to the Zappi for EV charging. Households with small batteries and large arrays often generate enough to fill the battery and still divert significant generation to the EV on summer days.

Installing a Zappi alongside an existing solar installation is a straightforward half-day job — CT clamp at the consumer unit, dedicated circuit, app commissioning. For new solar plus EV charger projects, we install both as a single job. Contact Amppro Electrical for a free survey across South and West Yorkshire.