You're managing your peak.
You're still leaving money on the table.
Careful peak management is the right first move. But at 1,200 km a month, stopping there costs the average EV commuter around €219 a year. Here's what the second move looks like.
€802
750 km
183
2.5 kW
The problem
Three things your charging strategy doesn't know.
1. When your monthly peak is already set.
Once the worst 15-minute window of the month has passed, additional consumption carries zero extra capacity tariff cost. But your charger doesn't know that. It keeps treating every hour the same.
2. That day-ahead prices aren't the real action.
Most dynamic tariffs publish tomorrow's prices at 3pm today. Elia's real-time imbalance price — settled every 15 minutes — can go five to ten times deeper negative during solar oversupply events. That's where the significant savings are.
3. How to run both strategies simultaneously.
Peak management and imbalance capture aren't in conflict — they're sequential. Manage the peak first. Then, when the peak is locked, charge hard during negative-price windows. The problem is timing both correctly without thinking about it every day.
The scenario.
A real profile. A modelled year.
This isn't an average household. It's a high-mileage EV commuter — the profile where the capacity tariff and imbalance pricing interact most meaningfully.
Marc
Software developer · Leuven · Flanders
1,200 km/month commuter
Vehicle
Hyundai IONIQ 6 LR
Charger
11 kW three-phase
Heat pump
5 kW, ~150 days/yr
Battery
77.4 kWh
Daily commute
55 km each way
Annual consumption
~9,580 kWh/yr
At 1,200 km per month, Marc is well above the ~750 km threshold where imbalance-price charging begins to outperform careful peak management on its own. He's also the kind of household that tried a dynamic tariff, found it required constant attention, and switched back. This is what the numbers look like across three approaches.
Three strategies. One year.
Strategy 01
Unmanaged — plug in when convenient
Avg monthly peak
Estimated annual total
€1,938
Baseline
Strategy 02
Peak management — slow overnight charging
Avg monthly peak
4.8 kW
Capacity cost/yr
€308
Estimated annual total
€1,355
10s two-phase
Peak management + imbalance
4.8 kW
€308
Estimated annual total
€1,136
- Unmanaged
- UPeak management (day-ahead)
- 10s two-phase
Where the €802 actually comes from
Peak management
€557/yr
Imbalance capture
€219/yr
Day-ahead shifting
€26/yr
The €557 peak management saving is available to anyone with a charging schedule. It doesn't require 10s, dynamic pricing, or any particular supplier. The additional €219 from imbalance capture is what automation makes possible — knowing in real time whether the monthly peak is set, and acting on it within seconds when a deep negative price event hits. No human does that reliably at 3am in April.
Simple to set up. Runs itself after that.
You configure your rules once. 10s and Home Assistant handle the sequencing — every charge, every quarter-hour, automatically.
1.
Set your monthly peak target
At the start of each billing month, the system knows your rolling 12-month average and sets a ceiling — keeping this month's peak at or below your target. All charging runs slowly enough to stay under it.
2.
Track peak status in real time
Once this month's worst 15 minutes has already happened, the constraint relaxes. The capacity tariff cost for the month is locked in. More consumption carries no further peak penalty.
3.
Charge fast when imbalance prices go negative
When Elia prices drop sharply — typically during solar oversupply in spring and autumn — the charger switches to full power. Your car absorbs cheap or negative-price electricity. The capacity bill doesn't move. The energy cost does — in your favour.
4.
Reset at the start of the next month
Conservative peak management restarts. The cycle repeats. You check a monthly summary if you want to. The system handles everything else.
When there's too much solar on the Belgian grid and not enough demand, prices go negative.
That happened for more than 8% of quarter-hours in 2024. On Elia's real-time imbalance feed — not the day-ahead forecast — those events can reach −€300/MWh or lower. A single 45-minute window at −€300/MWh, charging at 11 kW, earns you more than €2. Across 90 such events a year, it adds up to €219. Your 11 kW charger is the battery the grid needed. 10s makes sure it's switched on at exactly the right moment.
One more thing
What if your mileage is lower?
This use case is built for a 1,200 km/month commuter because that's where the two-phase strategy is most compelling. If your monthly mileage is closer to 500 km, careful peak management on a standard dynamic contract remains the financially optimal approach — the energy volume isn't large enough to make the imbalance capture outweigh the operational overhead. The break-even is roughly 750 km/month. Above it, the 10s approach adds a meaningful annual saving on top of what careful peak management already delivers. Below it, peak management alone is still a significant gain — and 10s still handles it automatically so you never have to think about it.
What these numbers don't include: supplier commercial margin, which applies to both standard dynamic and 10s options. At Marc's consumption level, the indicative add-on for a Belgian dynamic tariff is approximately €194–374/yr — common to any dynamic contract, not a 10s-specific cost. The figures above show the differential value of the strategy, not the total bill. See the full bill calculator for a complete estimate including margin.
Testimonials
Check out what our BETA users have to say
I've had solar for four years. I had no idea I was leaving this much money on the table. The first quarter on 10s more than covered the prosument tariff.
My EV now charges almost entirely during my solar peak or during negative-price windows. The combination is ridiculous. I genuinely feel like I'm gaming the system.
Set it up on a Saturday morning. Didn't touch it again. I check the dashboard sometimes just because it's satisfying to watch.
Solar injection savings calculator
Indicative estimate only. Based on 2024 Elia CWE annual average pricing data. See full disclaimer below.
⚠ Indicative estimate only. Not a contractual offer. Production estimated at 950 kWh/kWp/year (Belgian average). 10s injection income calculated using 2024 Elia CWE quarter-hour prices, assuming full real-time billing at actual spot rates. Standard buyback benchmark: Belgian market average fixed injection rate 2024 (€0.055/kWh). Actual results depend on your inverter, grid connection, DSO zone, and market conditions at time of use. Past pricing is not a guarantee of future earnings.
A smart supplier that really means it
Everything you need to know about solar injection with 10s
01. Do I need special hardware to connect my solar system?
No additional hardware is required. 10s works through Home Assistant, which connects to your existing inverter, EV charger, heat pump and other devices you already have. If your setup is already on Home Assistant, you're essentially ready to go.
02. How does 10s calculate my injection income?
Every kWh you inject into the grid is billed at the Elia real-time imbalance price for that specific 15-minute window. At the end of each quarter, you receive a detailed breakdown showing exactly which windows your energy was sold into and at what price. No averaging, no surprises.
03. What happens when prices go negative? Do I pay to inject?
Negative prices cut both ways. When prices go negative, consuming electricity earns you money — so your Home Assistant automatically switches on your big appliances during these windows. For injection during negative prices, 10s manages this intelligently so you're never caught out. We'll confirm the exact handling in your contract terms.
04. Does 10s help with the Flanders prosurment tariff?
Yes, indirectly. The prosument tariff is a fixed network cost you pay for having solar panels in Flanders — 10s can't eliminate it. But by maximising your self-consumption (running appliances during your own solar production) and boosting your injection income, 10s helps offset that cost significantly. Many customers find the net effect is positive.
05. Can I switch between the smart tariff and a standard tariff?
Yes. You stay in full control. You can switch appliances between smart (real-time) and standard (dynamic) tariff modes at any time, with a 48-hour notice period. For example, if you need your EV charged by a specific time regardless of price, you can temporarily switch it to a guaranteed charge mode.
06. Does 10s have access to my Home Assistant installation?
No. Your Home Assistant remains entirely under your control. 10s only sends you real-time price signals — your Home Assistant uses those signals to make decisions according to the rules you set. We never control your devices directly.