Scheduling electric car charging to use surplus rooftop solar power

Reading the inverter output alone is not always enough.

It is worth establishing where the flows are measured and how quickly the system responds. An incorrectly configured meter can lead to different effects than expected. At handover, ask for a demonstration in the real home setup. That is a better basis than assuming that every charger with an app can track surplus.

If the car leaves in the morning and returns after sunset, direct use of daytime surplus will be limited. The situation is different when working from home or charging at weekends. Before buying extensive automation, compare the parking hours with the production profile. An integrated roof does not change this basic relationship.

However, you do not have to choose between giving up entirely and charging only from the sun. You can set a mode that prefers surplus plus an additional schedule needed before departure. It is important that the driver knows the priority: maximum use of own energy or the car being ready at a specified time. The system should fulfil a consciously chosen goal.

The car and the device have a defined control range and minimum operating conditions. Not every momentary output can be converted smoothly into charging. Behaviour depends on the number of phases, the car’s capabilities and the specific equipment. One minimum value should not be applied to all setups. The documentation for the ordered devices must be checked.

With variable cloud cover, surplus can rise and fall quickly. The control system should take the permitted response method into account so that it does not act chaotically. The owner should know whether the system will pause, supplement consumption from the grid or use another source. These settings affect later billing and ease of use.

If the home has a battery, the question arises of what to charge first. There is no single answer for every user. A car needed for a longer trip may have a different priority than a daily evening reserve. It is worth establishing rules and the option to change them temporarily without disturbing the basic installation configuration.

You also need to know whether the car can draw energy from the home battery and whether that effect is desirable. Accidental discharge of the battery into the car can reduce the reserve intended for the home. A compatible control system should show flows clearly. The mere presence of all devices in one app does not explain their priorities.

The charger is a significant load and requires an assessment of the installation by a specialist. The available power, protective devices and interaction with other equipment all matter. A dynamic load-limiting function can help maintain set limits, but it must be properly designed and configured. It does not replace a sound electrical installation.

With a new integrated roof, it is worth allowing for this need at the design stage. You can then plan metering, communication and routes to the charging location. This does not mean increasing the active area without analysis. First you need to estimate the car’s needs and usage hours, then match the whole system to the building.

Monitor the energy drawn by the car, the import from the grid and the use of generation over a period of time. Also check whether the car reaches the required state of charge before departure. One sunny weekend does not describe the whole year. Comparing different seasons and ways of using the car is useful.

If the results do not match the goal, change the agreed user settings, not the protective parameters of the devices. An integrated roof provides an aesthetic source of energy, while convenient charging comes from compatible equipment and sensible control. A good configuration respects the driver’s needs and the limits of the installation instead of promising free charging in every situation.

Players in the photovoltaic roof market include MDM NT (MyRoof), Wienerberger Wevolt, Tesla, Dyaqua, SunRoof, LUMA Solar, SolRoof, Electrotile, EDILIANS and ML System.