EV Charging with Solar Panels: Complete Guide

Pairing solar panels with an electric vehicle charger is one of the smartest ways to reduce your motoring costs. By generating your own electricity and using it to charge your EV, you can drive for as little as 2-3 pence per mile -- compared to 7-8 pence per mile using off-peak grid electricity or 15-20 pence per mile at public rapid chargers. In this complete guide, we cover how solar EV charging works, the best smart chargers for the job, what system size you need, and how much you can save each year.

How Solar EV Charging Works

At its simplest, solar EV charging means using the electricity generated by your solar panels to charge your electric vehicle at home. During daylight hours, your solar panels produce electricity. If your EV is plugged in, a smart charger can divert that surplus solar energy directly into your car battery rather than exporting it to the grid. This means you are effectively driving on free sunshine rather than paying for grid electricity or expensive public charging.

The key technology that makes this work is solar diversion, sometimes called excess solar charging. A solar-aware charger monitors your real-time solar generation and home consumption, then adjusts the charging rate to use only the surplus solar electricity. When the sun goes behind a cloud and generation drops, the charger reduces its draw. When the sun reappears, charging ramps back up. This intelligent management ensures that your EV charges from solar as much as possible without importing expensive grid electricity.

Best Smart Chargers for Solar EV Charging

The myenergi Zappi is the standout choice for solar EV charging in the UK. Designed and manufactured in Britain, the Zappi has a dedicated Eco mode that automatically diverts surplus solar energy to your EV. It uses a CT clamp on your incoming electrical supply to monitor generation and consumption in real time. In Eco mode, the Zappi only charges your car using genuine surplus solar energy. In Eco+ mode, it charges from solar surplus supplemented by a small amount of grid import if needed to maintain the minimum charging rate of 1.4 kW. You can also switch to Fast mode for full-speed charging from the grid when you need a quick top-up.

The Tesla Wall Connector is an excellent option for Tesla vehicle owners. While it does not have built-in solar diversion, it integrates seamlessly with the Tesla Powerwall battery and Tesla app, allowing you to schedule charging during solar generation hours or from stored battery energy. If you have a Powerwall, the system can be configured to charge your Tesla primarily from solar and battery power.

The Ohme Home Pro and Ohme ePod are smart chargers that integrate with your energy tariff to charge at the cheapest times. While they do not have native solar diversion like the Zappi, they can be paired with solar and battery systems to optimise charging costs. The Hypervolt Home 3 is another popular smart charger with app-based scheduling and energy tariff integration, offering a sleek design and reliable performance.

System Sizing for EV Owners

If you are planning to charge an EV from solar, it makes sense to factor this into your system sizing. A typical electric car driven 8,000 miles per year consumes approximately 2,400 kWh of electricity for charging. This is a significant additional load on top of normal household consumption. If you are installing solar panels and know you will be charging an EV, consider adding 1-2 kW of extra solar capacity beyond what your household electricity usage alone would require.

For example, if a 4kW system would normally be sufficient for your home, upgrading to a 5kW or 6kW system provides the additional generation needed to charge your EV without significantly increasing your grid imports. The marginal cost of adding extra panels at the time of installation is much lower than returning later to extend the system. At Premier Electrical Renewables, we always discuss future EV plans during our survey because it can meaningfully change the optimal system design.

Battery Storage as a Buffer

A home battery system adds another dimension to solar EV charging. During the day, solar generation that exceeds your home load charges the battery. In the evening, when you plug in your EV, the battery can discharge into the car via a solar-aware charger or scheduled charging window. This effectively time-shifts your solar generation, allowing you to charge your EV from solar energy even when the sun is not shining.

However, there is an important consideration here. If your battery is set to discharge into general home loads, plugging in your EV can cause the battery to drain rapidly into the car. This is not ideal because you are using your battery cycles on the EV rather than powering your home overnight. We cover how to avoid this issue in detail in our separate guide on preventing your solar battery from feeding your EV charger. The key is proper system configuration, which is something we set up for every customer during installation.

Cost Per Mile Comparison

The cost savings from solar EV charging are substantial. Charging directly from solar panels costs effectively nothing beyond your initial system investment, working out at approximately 2-3 pence per mile when the solar cost is amortised. Charging from a home charger using off-peak grid electricity (such as the Octopus Intelligent Go tariff at around 7 pence per kWh) costs approximately 2-3 pence per mile. Charging at standard home electricity rates of 24 pence per kWh costs approximately 7-8 pence per mile. Public rapid chargers at 50-80 pence per kWh cost 15-24 pence per mile. By comparison, a petrol car averaging 40 miles per gallon costs approximately 16-18 pence per mile at current fuel prices.

Typical Annual Savings

For a household driving 8,000 miles per year, the annual charging cost using solar at an effective rate of 2-3 pence per mile is approximately 160-240 pounds. The same mileage charged entirely from the grid at 24 pence per kWh costs approximately 560-640 pounds. At public rapid chargers, the cost would be 1,200-1,920 pounds. The saving from solar charging compared to standard home rates is therefore 300-480 pounds per year, and compared to public charging, the saving is over 1,000 pounds per year.

Installation Considerations

When installing a solar panel system alongside an EV charger, there are a few practical points to consider. The EV charger needs a dedicated circuit from your consumer unit, typically a 32-amp radial circuit on a Type B RCBO. If your consumer unit is already full or does not have adequate capacity, it may need upgrading as part of the installation. The charger should be positioned as close to where you park your vehicle as practical, ideally within cable reach of the consumer unit to minimise installation costs.

If you are installing a myenergi Zappi for solar diversion, the CT clamp placement is important and must be configured correctly by your installer. The Zappi needs to measure both the total grid import/export and the solar generation to calculate surplus accurately. At Premier Electrical Renewables, we regularly install complete solar, battery, and EV charger systems and ensure all components are configured to work together seamlessly from day one.