How does Stekker incorporate your solar panels?
Stekker can include the solar panels at your site in the charging schedule. Your panels are configured with the following specifications:
- Number of panels and power per panel (in Wp, up to a maximum of 800 Wp per panel)
- Orientation (azimuth) — the compass direction your panels face (0°–360°, where 180° = due south)
- Tilt angle (declination) — the angle relative to horizontal (0°–180°)
- Inverter specifications — optional: the number of phases and current per phase of the inverter
Stekker supports up to 3 solar installations per site. This is useful when you have panels on multiple roof sections with different orientations or tilt angles. Each installation gets its own name and specifications.
The total nominal power of an installation is calculated as the number of panels multiplied by the power per panel. For example, an installation with 40 panels of 410 Wp has a nominal power of 16,400 Wp (16.4 kWp).
Charging on your own solar power
Stekker automatically optimizes whether it is more cost-effective to charge from the grid at that moment, or to wait for your own solar power.
The logic works as follows: Stekker compares the current market price for grid electricity with the value of your own solar production. Unused solar power earns you less than what you pay for grid electricity — the difference is the grid costs you save by using your own power.
Stekker uses a threshold of EUR 0.09 per kWh as a reference for those grid costs. When the market price of grid electricity (including energy tax and surcharges) is lower than the value of your solar power minus that EUR 0.09, charging is shifted to hours with solar production. If grid electricity is cheaper at that moment, Stekker simply charges from the grid.
The result: your vehicles charge as much as possible on your own solar power when that is more cost-effective, without you having to do anything.
Combination with peak shaving
Solar production reduces the net load on your grid connection. Stekker automatically takes this into account when calculating the available charging capacity.
In practice: if your solar panels are producing 15 kW at a given moment, Stekker can count that 15 kW as available capacity on top of your contracted grid capacity. The total charging power that Stekker can deploy is bounded by the actual solar production, ensuring your grid connection is never overloaded.
This works together with the peak shaving functionality: the combination of your grid capacity and your solar production determines the maximum power available for charging at any given moment.
Forecasts and planning
Stekker fetches solar forecasts every hour for sites with configured solar panels. These forecasts are based on the GPS coordinates of your site and the specific panel configuration (orientation, tilt angle, power).
The forecasts are interpolated to 15-minute intervals and incorporated into the charging schedule. Stekker uses this data to determine for each quarter-hour of the coming day how much solar production is expected, and plans vehicle charging accordingly.
During variable weather or cloud cover, forecasts are updated every hour. This way, the system continuously adjusts the schedule based on the most recent forecast.
Setup
Solar panels are configured by Stekker during the installation of your site. The following information is required:
- Number of panels per roof section or installation
- Power per panel in Wp (watt-peak)
- Orientation in degrees (azimuth: 0° = north, 90° = east, 180° = south, 270° = west)
- Tilt angle in degrees (0° = flat, 90° = vertical)
- Optional: inverter specifications (number of phases, current per phase)
Do you have panels on multiple roof sections with different orientations or tilt angles? These are configured as separate installations (maximum 3 per site).
Additionally, the GPS location of your site must be set so that Stekker can fetch solar forecasts specific to your location.
