Charge HQ relies on metering of energy flows from solar inverters, home batteries and energy monitors which we access over the Internet via APIs.
We use this data to determine:
We then combine this with the user settings in the app to determine when and at what rate to charge the EV.
Where only solar production is monitored, we can set EV charging to match the amount of energy being produced by the solar.
Without monitoring the grid connection we don’t know how much of the solar production is in excess to that which the home is using before we start EV charging.
When EV charging control is based only on solar production monitoring, it will use all of the solar energy produced and any other home energy consumption will be drawn from the grid.
Where both the solar production and the homes grid connection are monitored, Charge HQ will know exactly how much excess solar energy is being produced above the needs of the home.
EV charging can then be set to match this excess production, minimising the use of grid energy either by the EV or the home.
Grid monitoring with a rooftop solar system is most often provided via an optional meter which is purchased with your solar system. This meter will normally give you visibility of your home energy consumption in the smartphone app for your solar inverter.
Grid monitoring may also be provided by a standalone energy monitor, or in some cases may be built-in to the inverter.
To get the most value from Charge HQ, we recommend you have both solar production and grid monitoring in place.
All home battery installations monitor solar production, grid import/export and the home energy consumption by default. Charge HQ can collect all three data sets from supported home batteries (or the supported solar inverter it is connected to).
For home batteries, in addition to monitoring the rate of charge or discharge we also monitor the state of charge of the battery. This lets us give you the choice of prioritising the charging of your home battery, or your EV as excess solar energy becomes available each day.
Where the home battery is enrolled in a VPP, Charge HQ will use the battery monitoring to take into account VPP initiated charge and discharge events.
Where charging is controlled via a compatible wall charger, Charge HQ can only monitor the amount of energy that is used for charging the EV.
Where charging is controlled via direct vehicle integration (currently only Tesla), we can also monitor the state of charge of the vehicle battery.
This allows more flexible scheduling of charging and can increase the amount of EV charging from rooftop solar energy. For example, we can set a charge limit of 90% when charging from solar, but if the EV has been unable to charge from solar during the day we can set an overnight grid top-up charge limit of 50%. This ensures the EV has reasonable range the next day, but also leaves plenty of room in the battery to absorb excess solar if it’s available the next day.
Without monitoring the vehicle state of charge, an overnight grid top-up acts blindly. It can charge up to the the vehicles internal charge limit - reducing the ability to charge from solar the next day. Alternately it can supply a pre-defined amount of energy (e.g. 30 kWh), but lacking awareness of the vehicles battery state this might leave the EV with limited range, or provide more charge than is needed and limit the ability to charge from solar the next day.