Solar-Powered EV Charging: Smart Scheduling to Maximise Free Miles

If you have solar panels and an electric vehicle, you already have the ingredients for near-zero-cost driving. The missing piece is timing — getting your charger to draw power when your panels are producing most, and filling the gap cheaply overnight. This guide explains exactly how to do that, step by step.

Why Timing Is Everything for Solar EV Charging

Solar output in the UK peaks between roughly 10am and 2pm on a clear day, when the sun is highest in the sky. According to PVGIS data from the European Commission's Joint Research Centre, a south-facing 4 kWp system in southern England generates around 3,500–3,700 kWh per year — with the lion's share produced during those midday hours in spring and summer.

A typical 60–77 kWh EV battery needs 15–20 kWh to add 60 miles of range. On a sunny summer day, a 4 kWp system can easily produce 20+ kWh between 9am and 4pm — enough to fully replenish a daily commute's worth of charge without touching the grid. The challenge is that most people plug in overnight and miss the solar window entirely. Smart scheduling solves this.

For more on how UK solar output varies by region and season, see our guide to solar panel output in the UK.

Solar Divert Mode: How Smart Chargers Use Surplus Energy

Solar divert (also called solar boost or eco-smart charging) automatically routes surplus solar generation into your EV rather than exporting it to the grid for a few pence per unit. Here is how the two leading approaches work:

Zappi by myenergi — ECO and ECO+ Modes

The Zappi is the UK's most popular solar-divert EV charger. It uses a CT (current transformer) clamp on your incoming supply cable to measure your home's real-time generation and consumption. Two solar-aware modes are available:

• ECO mode — charges at a minimum of 1.4 kW at all times but reduces grid draw by matching surplus solar first. Good for ensuring a guaranteed minimum charge rate even on cloudy days.
• ECO+ mode — charges only when you have surplus generation above the 1.4 kW EV minimum. If solar output drops (cloud cover, early morning), charging pauses entirely rather than pulling from the grid. This delivers the maximum free-miles result on sunny days.

The Zappi's Minimum Green Level (MGL) slider lets you blend the two behaviours — setting MGL to 100% gives pure solar-only charging; lowering it allows a small grid top-up when generation dips slightly.

Ohme ePod — Solar Boost

Ohme's ePod charger (7.4 kW, from £949 including standard installation) also ships with a CT clamp for units installed from January 2023 onwards. Its Solar Boost feature, controlled via the Ohme app, detects surplus energy from your solar system and diverts it to your EV in real time. It maintains a minimum 5 A charge rate and supplements with grid power if needed, adjusting dynamically as output changes with cloud cover. Ohme's app also integrates directly with most UK tariffs — meaning Solar Boost and scheduled cheap-rate charging can work in tandem via a single interface.

Solar Divert vs Scheduled Charging: When to Use Each

The two approaches suit different situations, and the best setup usually combines both:

If your car is away during the day, solar divert is limited to weekends and annual leave. In this case, a smart overnight tariff becomes your primary cost-saving tool, with solar divert as a free bonus on days the car is at home.

For a deeper comparison of charger options that support solar divert, see our best EV chargers for solar panels in the UK guide.

Combining Solar Divert with a Smart Overnight Tariff

Octopus Intelligent Octopus Go is widely regarded as the UK's leading smart EV tariff. It offers a guaranteed six-hour cheap overnight window (typically 23:30–05:30) at around 8p/kWh — compared to the April 2026 Ofgem price-cap standard rate of 24.67p/kWh. Octopus's smart dispatch system automatically shifts more charging into additional cheap slots when the grid has surplus renewable power, reducing costs further without any manual input.

The recommended two-mode strategy is:

1. Daytime (solar window): Car plugged in and set to ECO+/Solar Boost. Charges exclusively on surplus solar — effectively free miles.
2. Overnight (11:30pm–5:30am): Intelligent Octopus Go tops the battery up to your target state of charge at 8p/kWh, ensuring you always start the day with enough range regardless of yesterday's sunshine.

This hybrid approach can cut per-mile energy costs to a blended figure well below 2p/mile for high-solar households.

How Many Free Miles Can a UK Solar System Deliver?

The rough calculation for a 4 kWp south-facing system in England:

• Annual generation: approximately 3,400–3,700 kWh (PVGIS data for central England; London closer to 3,680 kWh/yr at 920 kWh/kWp)
• Self-consumption available for EV: assume 40–50% of annual generation is surplus after household use (higher if you're often out during the day), so roughly 1,360–1,850 kWh directed to EV charging
• EV efficiency: most modern EVs achieve 3.5–4.5 miles per kWh in real UK mixed driving; use 4 miles/kWh as a mid-point
• Free miles per year: 1,360 × 4 = approximately 5,400 miles on the conservative end; up to 7,400 miles on a warm, high-solar year with good self-consumption

The average UK driver covers around 7,400 miles per year (DfT National Travel Survey). In a best-case summer-heavy scenario, a well-optimised solar EV setup could cover the entire average annual mileage in free solar miles — though realistically, a mix of solar and cheap overnight tariff charging is more likely for most households.

Practical Tips to Maximise Your Free Miles

Small changes to your routine can significantly increase the solar miles you capture:

• Set a charge window in your car or charger app to block charging from 7am–11pm except when solar surplus is detected. This prevents accidental daytime grid charging while the panels are working.
• Use a monitoring app (myenergi app for Zappi, Ohme app, or a solar inverter app like SolarEdge or Enphase) to check yesterday's generation and adjust your charge target accordingly.
• Plug in earlier on sunny days — ECO+ only charges when surplus is present, but the car needs to be connected and ready. Plugging in at 9am on a clear June day means capturing two or three extra hours of peak-hours solar versus plugging in at noon.
• Home battery storage as a buffer: if you have a home battery (e.g. GivEnergy or Powerwall), you can store lunchtime solar surplus and transfer it to the car later in the afternoon when output fades. This smooths out cloud gaps and extends the effective solar charging window. See our overview of charging an EV with solar panels for more on this setup.
• Orientate your schedule around UK solar peak hours: 10am–2pm in summer, 11am–1pm in winter. If you have flexibility in when you work from home, those hours are prime solar-divert time.
• South-facing roof pitch matters: a 30–35° pitch facing within 45° of south gives optimal year-round yield. East or west roofs still generate useful surplus but peak earlier or later in the day.

Getting Started

The simplest path to solar EV charging is installing a Zappi or Ohme ePod alongside your solar system — or adding a compatible charger if panels are already fitted. Both require a CT clamp installation (usually included in the charger price or fitting quote) and an app to configure your charging preferences.

If you don't yet have solar panels, pairing them with an EV is one of the strongest financial cases for going solar in 2026: you displace expensive grid electricity with self-generated power at effectively zero marginal cost. Read our full guide on EV charging with solar to understand the full system setup and costs.