The Problem Solar Diversion Solves
When your solar PV system generates more electricity than your home needs at that moment, the excess is automatically exported to the grid via ESB Networks. This is called export and you are compensated for it under Ireland’s Microgeneration Support Scheme (MSS) — typically at 18–24 c/kWh depending on your supplier.
This seems like a good deal until you compare it to the electricity you import during the rest of the day at 28–35 c/kWh for general household use, or the electricity you import at night for EV charging at 12–15 c/kWh on a smart tariff.
The maths shows that exported electricity at 20 c/kWh is less valuable than imported electricity that you could avoid buying at 30 c/kWh (daytime) or 13 c/kWh (night). Solar diversion captures excess solar energy before it leaves your home and redirects it to a useful load — most commonly an EV charger or an immersion heater.
What Is Solar Diversion?
Solar diversion is a technique where excess solar generation is automatically redirected to a controllable load (EV charger, immersion heater, or battery) rather than being exported to the grid.
The key hardware is a diversion controller that:
- Monitors power flow at the grid connection point using a CT (current transformer) clamp
- Detects when the system is about to export (solar > household demand)
- Increases the load on the diversion device (EV charger) by the exact amount of surplus
- Continuously adjusts in real time as solar output and household load change
The net effect: electricity that would have been exported at 20 c/kWh is instead used to charge your EV — effectively at 0 c/kWh (free solar energy) rather than grid electricity at 13 c/kWh (night rate) or 30 c/kWh (day rate).
How the CT Clamp Works
The current transformer (CT) clamp is a non-invasive sensor that clips around the main supply cable at your meter or consumer unit. It measures the current flowing in or out of the property — specifically:
- Positive current flow (from grid): you are importing electricity
- Negative current flow (to grid): you are exporting electricity (surplus solar)
The CT clamp sends this real-time current measurement to the diversion controller (the EV charger or a standalone diverter). The controller uses this data to determine how much power it can safely divert.
Important: The CT clamp does not interrupt the electrical circuit and does not require any modification to your meter or grid connection. It is a sensor only. A competent electrician installs it in under 30 minutes.
Solar Diversion EV Chargers in Ireland
MyEnergi Zappi
The Zappi is the leading solar diversion EV charger in Ireland and the UK. It includes a CT clamp as standard and is purpose-built for solar integration.
In Eco mode, the Zappi continuously adjusts its charging current based on CT clamp data, charging the EV at the available solar surplus rate. If surplus drops below the minimum charge current (6A / 1.4 kW), the Zappi draws a small amount from the grid to maintain minimum charging.
In Eco+ mode, the Zappi charges exclusively from solar surplus, pausing entirely if surplus falls below the minimum. This is the strictest solar-only mode and maximises self-consumption but may result in slower or intermittent charging on cloudy days.
The Zappi can also be used with a Boost timer — a scheduled grid charge window at the end of the day that tops up the EV to a target level using cheap night-rate electricity, complementing whatever solar diversion achieved during the day.
Ohme Home Pro with CT Clamp
The Ohme Home Pro supports solar diversion mode when a compatible CT clamp is installed. The functionality is similar to the Zappi’s Eco mode — the Ohme monitors surplus solar and adjusts charge rate accordingly. The Ohme app displays real-time solar contribution to each charging session.
The Ohme’s solar diversion is competent but less refined than the Zappi’s for pure solar-first scenarios. The advantage is that Ohme also has excellent tariff integration for the grid top-up element.
Easee One with Third-Party Diverter
The Easee One itself does not have built-in solar diversion mode (unlike the Zappi). However, the Easee ecosystem supports OCPP-based control from third-party energy management systems (e.g., SolarEdge Home, Loxone, Home Assistant) that can implement solar diversion logic by sending OCPP commands to the charger.
For Easee owners with compatible solar inverters, this approach achieves solar diversion but requires a more complex setup than the Zappi’s plug-and-play implementation.
How Much Solar Can Actually Go to EV Charging?
Solar diversion to EV charging is most effective when:
- The EV is parked at home during solar generation hours — typically 10:00–16:00 in Ireland
- Solar generation is consistent — clear or partly cloudy days, ideally summer months
- The array is large enough — a 4 kW+ array on a south-facing roof generates meaningful surplus after household base load (refrigerator, standby, router, etc.)
For a typical Irish home with a 4 kW solar array and a household base load of 0.5 kW:
- On a sunny day (3 kW average output): surplus of ~2.5 kW → Zappi charges EV at 2.5 kW for 8 hours = 20 kWh (approximately 90–100 km range added)
- On a partly cloudy day (1.5 kW average output): surplus of ~1 kW → 8 kWh (approximately 40 km range)
- On a typical Irish overcast day (0.3 kW output): surplus of ~0 → no solar diversion; night tariff used
Seasonally, solar diversion is most valuable May–September. In winter, Irish solar generation is insufficient for meaningful EV diversion and the night tariff does the heavy lifting.
Annual solar EV contribution estimate for 4 kW array in Ireland: 400–800 kWh (typical range depending on roof orientation, shading, and occupancy pattern). At a displaced grid rate of 25 c/kWh (day rate saved), this saves approximately €100–€200 per year in avoided grid electricity.
For larger arrays (6–8 kW), the contribution and saving scales proportionally.
Financial Summary: Is It Worth Installing Solar for EV Charging?
Solar diversion alone does not justify a solar PV installation — the economics of solar PV rest on household self-consumption, export income, and long-term energy cost protection.
But if you are considering solar PV for general household electricity savings, the addition of EV solar diversion:
- Adds approximately €100–€200/year in EV charging savings
- Increases your solar self-consumption rate (less exported at low rates)
- Enhances the payback case for the solar array
- Requires only a Zappi charger (instead of a standard charger) — adding approximately €100–€200 to the charger installation cost
The MyEnergi Zappi + solar PV is the natural combination for Irish homeowners who are doing both. The incremental cost of the Zappi over a standard charger is modest compared to the value it captures over the system’s lifetime.
