Charging an electric vehicle when a PV system is producing can increase local use of solar electricity. The useful charging window depends on more than a sunny forecast: the vehicle must be connected, the battery must have sufficient space, household or business demand must be considered, and the required departure charge must still be met. A generation forecast is an input to the charging plan rather than a guarantee of available surplus.
Estimate surplus instead of total generation
Expected PV production does not all belong to the charger. Other on-site loads consume electricity at the same time. The charging controller needs either a forecast of those loads or an explicit method for reacting to measured surplus. Where a stationary battery is present, its charging priorities and state of charge also influence the allocation. Define the electrical measurement boundary before comparing forecast and consumption.
Plan around the user's actual constraints
Record connection times, departure deadlines, charger power limits and the minimum charge required. A plan that maximises solar use but leaves the vehicle undercharged is not a useful result. Some flexibility can be reserved for later forecast updates; essential charging should have a clear fallback when the weather changes or the vehicle disconnects unexpectedly.
Use updates and measured conditions
PV output can change rapidly as clouds pass. A day-ahead plan establishes an expected opportunity, while updated forecasts and real-time measurements can adjust the charging rate. The controller must respect equipment and connection limits. Forecast integration should also specify what happens if data delivery fails, rather than letting an unavailable forecast prevent necessary charging.
Evaluate energy and service together
Useful measures include solar electricity used by the vehicle, grid energy imported for charging and whether departure requirements were met. Compare equivalent journeys and operating conditions instead of selecting a favourable sunny day. Self-consumption and self-sufficiency are different ratios, so state the denominator. Financial value depends on the actual import tariff, export remuneration and charging arrangement, not only on the amount of local energy used.
What this means for a pilot
Start with one installation whose metering, charger control and operating constraints are known. Archive the forecast, the planned schedule and actual charging behaviour. Review cloudy days and missed data as carefully as successful days. The original 2016 article highlighted solar-led charging as a practical use of prediction; a current implementation still needs verified equipment compatibility and a tested control workflow.
Avoid confusing optimisation targets
More local solar consumption, lower cost and lower peak import are different objectives. A schedule that improves one may not maximise the others. For example, charging earlier can secure a departure requirement while reducing the flexibility available for a later sunny interval. Choose the priority explicitly and document the constraints rather than judging the controller from one favourable metric.
Include forecast error in the plan
A charging schedule should remain workable if solar production is lower than expected. Consider the minimum charging energy that must be delivered before departure and the remaining time available at the charger limit. Reserve a practical fallback instead of committing every interval to an optimistic solar forecast. Replanning can then use improved information while maintaining the service requirement.
Keep the pilot measurable
Synchronise charger energy, site import or export and PV generation timestamps. Record connection and disconnection events, because user behaviour can explain differences between a planned and executed schedule. If one of these series is unavailable, state which outcomes cannot be measured directly. A fair comparison should include similar travel needs and connection windows. The result is evidence about a specific installation and operating policy, not a universal promise that any vehicle can be charged entirely from solar generation.