EV charging and solar
Charge Your EV for Free with Solar: The Zappi Explained
A standard EV charger draws whatever it needs from the grid. The myenergi Zappi watches your solar output in real time and adjusts its charge rate to use your surplus first, so the electricity going into your car is the electricity your panels are generating for nothing.
Helpful video reference. ChargedEV's "An Honest Look at the myenergi zappi" gives a fair assessment of how the Zappi performs in practice, covering all three charge modes and the real-world differences between them. ChargedEV is a UK EV charging media and installation company.
This is notifiable electrical work
The Zappi is a 7kW hardwired EV charger, not a plug-in accessory. Installation requires a qualified electrician who will connect it to a dedicated circuit in your consumer unit and submit a DNO notification under G98. This is not DIY work. If you are also installing solar panels at the same time, an MCS-certified installer can handle the full integration in one job.
1. What the Zappi does differently from a standard charger
Most EV chargers are simple: plug in the car, set a time, and the charger draws a fixed amount of power from the grid. The Zappi adds a current transformer (CT clamp) on your incoming supply, which lets it see what your solar panels are generating and what the rest of the house is using at any given moment. It then adjusts the charge rate in real time, diverting your surplus solar to the car instead of letting it trickle to the grid at a low export rate.
This matters because the Smart Export Guarantee rates from most suppliers are considerably lower than the cost of importing electricity. If your car is at home during the day when your solar is generating, the Zappi can fill it up using power that would otherwise earn you only a few pence per unit, turning that surplus into transport.
2. The three charge modes and when to use each
The Zappi has three charge modes, and the right one depends on whether you need the car charged by a specific time or are happy to wait for the sun:
FAST mode charges at the full 7kW rate regardless of what your solar is doing. The car charges as quickly as possible, drawing mainly from the grid. Use this when you need the car charged quickly or are on a low overnight tariff.
ECO mode sets a minimum charge rate of 1.4kW (the minimum the Zappi will ever draw) and then scales up automatically as surplus solar becomes available, blending grid and solar. The car always charges at some rate, but uses as much solar as possible.
ECO+ mode waits until there is enough surplus solar before starting at all. If your panels are not generating surplus, the car does not charge. This gives you the most solar-powered miles but means the car may not charge on overcast days or in winter unless you switch to ECO or FAST.
3. What you need for solar diverting to work
To divert solar surplus, the Zappi needs a way to measure your solar generation. This is usually done with a CT clamp fitted to the AC output cable of your solar inverter, or wirelessly via myenergi's Harvi sensor if running a cable is impractical. Your installer will advise which is cleaner for your setup.
You do not need a myenergi solar system: the Zappi works with any make of solar inverter. You also do not need a battery. But if you do have a home battery, the Zappi can be configured to prioritise charging the battery first, then divert surplus to the car once the battery reaches a threshold you set, avoiding situations where the car drains the battery you were relying on for evening use.
4. What the installation involves
The Zappi mounts on an external wall near where you park. It needs a dedicated 7kW circuit back to the consumer unit: your electrician will install a new breaker, run armoured cable from the unit to the charger location, and fit the CT clamp on the solar inverter output. The DNO must be notified under G98 before the charger is energised, which is part of a standard EV charger installation in the UK.
If you are having solar installed at the same time, combining both jobs with an MCS-certified installer is the most cost-effective route. We can design a system where the Zappi, solar, and battery (if included) are all integrated from day one, without the risk of a CT clamp positioned incorrectly by a later installer.
Frequently Asked Questions
Do I need a Zappi to charge my EV with solar?
No. Any EV charger will technically work alongside solar panels, because both feed into your home's circuits. The difference with a solar-aware charger like the Zappi is that it actively adjusts its charging rate to match your surplus solar output, so you actually use more of your own generation rather than sending it to the grid at a low export rate.
How much solar do I need to charge an EV meaningfully?
The Zappi's ECO+ mode needs at least 1.4kW of surplus solar before it will start charging. A typical 4kWp roof system on a sunny summer day might generate 3-4kW at peak, giving you roughly 10-15 miles of range per hour of solar charging. In winter or on overcast days, output is much lower and ECO or FAST mode may be more practical.
Can the Zappi work with a home battery as well as solar?
Yes, and this is one of the Zappi's more useful features. When connected to a myenergi hub alongside a battery system (such as the Libbi), it can be configured to prioritise charging the home battery first, then divert surplus to the car once the battery reaches a set threshold. This avoids draining your home battery unnecessarily.