Anatomy of a Charging Session
Every charging session in Stekker follows a lifecycle:
- Start — Your vehicle plugs in and Stekker detects the connection.
- Planning — The optimization engine checks electricity prices, your departure time, and the energy needed. It creates a charging schedule targeting the cheapest hours.
- Charging — Stekker sends smart charging profiles to your charge point, controlling when and how fast energy flows.
- End — Your vehicle reaches the target level or you unplug. Stekker records the final metrics and calculates your savings.
Key Metrics in Your Session
Each completed session shows several numbers:
- Energy (kWh) — The total amount of electricity delivered to your vehicle.
- Duration — The total time your vehicle was connected, from plug-in to plug-out.
- Power (kW) — The rate at which energy was delivered. Higher power means faster charging.
- Cost — What you actually paid for the energy, based on the real hourly prices during the moments Stekker scheduled charging.
How Savings Are Calculated
Stekker calculates savings by comparing two scenarios for every session:
Baseline Cost (Uncontrolled Charging)
This is what you would have paid without smart charging. The baseline assumes your charger would have started immediately at maximum power when you plugged in — consuming energy at whatever prices happened to be active at that moment. This is how most chargers work without optimization.
Smart Cost (Optimized Charging)
This is what you actually paid. Stekker deferred charging to the cheapest available hours within your window, so the same amount of energy was delivered at lower prices.
Your Savings
The difference between baseline and smart cost is your saving for that session. If uncontrolled charging would have cost €12.50 and Stekker achieved it for €8.20, your saving is €4.30.
Where to Find Your Savings
Your dashboard shows savings at two levels:
- Per session — Each session card displays the cost and saving amount.
- Cumulative — Your total savings over time, across all sessions and vehicles. This number grows with every optimized session.
Why Some Sessions Show More Savings Than Others
Several factors influence how much you save on any given session:
- Price volatility — Days with large price swings between peak and off-peak hours offer more room for optimization. A flat price profile means less to gain.
- Flexibility — The longer your charging window (time between plug-in and departure), the more cheap hours Stekker can access. A 12-hour window offers far more savings potential than a 3-hour window.
- Energy needed — Sessions requiring more energy naturally have higher absolute savings, because there’s more kWh to shift to cheaper hours.
- Time of plug-in — Plugging in during expensive evening hours and letting Stekker defer to cheap nighttime hours maximizes the price difference.
- Negative prices — Sessions that coincide with negative price periods can show exceptionally high savings. See Dynamic Pricing: How Stekker Uses Electricity Markets for more on this.
Building Up Savings Over Time
Individual session savings might seem modest, but they compound quickly. A fleet of vehicles charging nightly can accumulate substantial savings within weeks. Your cumulative savings counter on the dashboard tracks this progress across all your charge points and vehicles.
For details on what your charging hardware needs to support smart optimization, see Charge Point Compatibility and Requirements.
