I actually meant to post this full breakdown yesterday, but I fell down a deep, dark rabbit hole of data formatting. Let me tell you, European number formatting is my villain origin story. Trying to figure out if 1.083 means "one point zero eight" or "a thousand and eighty-three" while simultaneously confusing instantaneous power (kW) with actual energy volume (kWh) almost made my spreadsheet catch fire. 🔥
I literally spent hours staring at my screen until 2 AM, wondering if my solar panels were severely underperforming or if Excel was just actively gaslighting me. But the digital smoke has finally cleared! To figure out exactly what happened in our home in March 2026, I pulled data from everywhere: our SMA inverter (Solar), the Fluvius digital meter (Grid), the HomeWizard P1 dongle, our Plug-in Battery logs, and the EV charging app.
Here are the hard numbers of our 1-phase setup:
📈 Massive Usage, Tiny Bill
We consumed a whopping 955 kWh in March. A massive 57% of that (546 kWh) went straight into our two EVs. Yet, our total net electricity bill—including all taxes, grid fees, fixed costs, and the capacity tariff—was only €191.88. Try fueling two cars for a whole month with petrol for that amount!
Dynamic tariffs force you to think about when you consume, and the financial payoff is just undeniable.
☀️ Solar Self-Consumption FTW
Our SMA panels generated 318 kWh of glorious sunshine. Because we actively manage our loads and dynamically charge the cars during the cheapest hours (usually right in the middle of the day when the sun is at its peak), we instantly gobbled up 71% (228 kWh) of our own solar power. Only 90 kWh leaked back into the grid. That direct self-consumption immediately shaved €43.20 off our bill. It is incredibly satisfying to watch the cars soak up those rays before the grid even notices we are generating anything.
🔋 The Little Plug-in Battery That Could
Halfway through March, we hooked up a plug-in home battery. It’s a relatively small system, but it acts as a brilliant, automated financial buffer. The difference between the energy going in and coming out represents the normal conversion losses (AC to DC and back), but even with that efficiency tax, the math checks out beautifully. In just 14 days of real data, here is what the little box achieved:
Charging: It stored 48 kWh. About 33 kWh of that was free solar power, and 15 kWh was dirt-cheap grid power grabbed during low-price hours. The total cost (including missed injection revenue for the solar part) was just €4.90.
Discharging: It fed 38 kWh back into our living room during the expensive evening peaks. If we had bought that power from the grid, it would have cost us €9.59.
Net Profit: A hard, clean profit of €4.69 in two weeks. Bring on the negative summer prices!
They have an update planned so that it knows when to charge from the next (cheap prices) and only delivers back to the house when the prices do peak. Currently I do this manually by forcing it to charge on demand.
⚖️ Living on the Edge (Safely)
Running two EV chargers, a battery, and a household on a standard 1-phase connection sounds like a recipe for a blown main fuse. But thanks to perfect load balancing, our absolute highest quarter-hourly peak was just 7.52 kW. We squeezed every drop of value out of our capacity tariff without ever plunging the house into darkness.
🌷 Enter Spring: Cooking with Sunshine
Now that April is here and the clocks have officially sprung forward, the energy game is shifting again. We are entering the golden season for dynamic tariffs and solar setups. In the depths of winter, by the time it is 6:00 PM and you start turning on the induction cooktop, the oven, and the air fryer, the sun is long gone. You are completely at the mercy of the grid's most expensive evening rates, heavily relying on the battery to soften the blow.
But spring changes everything! Because the days are getting noticeably longer, the sun is still high enough in the sky to power our heavy kitchen appliances during dinnertime. Instead of draining the battery to roast some vegetables or boil pasta, the solar panels will take the brunt of the hit. It completely reshapes our daily load profile. This means we will be able to directly consume even more of our own solar power right when we need it most, bypassing both the grid and the battery entirely. I am extremely curious to see how this extended daylight flattens our evening peak loads in next month's report.
🕵️♂️ The Unsolved Mystery... Despite surviving the comma/decimal dot disaster, the fact remains: somehow, there is still a slight discrepancy between the power we supposedly generated and what we actually consumed and injected. It’s like the energy version of the sock that disappears in the washing machine. We have an energy gremlin somewhere in the logs.
Next Steps: For next month's report, I'm definitely streamlining the data exports to avoid the formatting nightmares, and I'll be hunting down that missing discrepancy!
Are there any other data nerds here running HomeWizard P1 dongles, plug-in batteries, and dynamic tariffs? I'd love to see how your setups are handling the EV load!