Two Marstek Venus plug-in batteries, a set of solar panels and a smart meter, as measured in my own house. Each battery sits behind a Tapo smart plug, so the charge and discharge figures below are what the wall socket saw — losses and all. Home Assistant pushes a fresh snapshot to this page every 30 seconds.
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| Battery | Charged | Discharged | Round-trip |
|---|---|---|---|
| Meterkast | – | – | – |
| Werkkamer | – | – | – |
| Combined | – | – | – |
kWh at the socket, so the round-trip already includes the inverter and standby losses. Today's figure only settles once the batteries have given back what they took in — before the evening it reads low, because the difference is still sitting in them. That is why the headline above counts closed days instead.
| Over – | Energy | Share |
|---|---|---|
| Solar harvest | – | |
| Used at home | – | – |
| Exported to the grid | – | |
| Taken from the grid | – | |
| House consumption | – | |
| Into the batteries | – | |
| Out of the batteries | – | – |
Over the whole life of the batteries they have handed back – that never had to come through the meter.
| Month | Solar | Kept | From grid | Self‑sufficient | Battery in / out | Round‑trip |
|---|
Every figure is in kWh unless it says otherwise. Kept is the share of the harvest that stayed in the house; self‑sufficient is the share of everything used that did not come off the grid. Read the round‑trip column downwards — that is where wear shows.
| Battery | Full cycles | Charged over its life | Round‑trip |
|---|---|---|---|
| Meterkast | – | – | – |
| Werkkamer | – | – | – |
| Combined | – | – | – |
Capacity is not measured here — that would need a controlled full discharge. What these three columns do track is what actually moves as a cell ages: the cycle count the BMS keeps, the energy that has passed through, and how much of it comes back out.
Solar, import and export come from the P1 smart meter and the inverter; charge and discharge come from the Tapo plug in front of each battery. Used at home is the harvest minus whatever left through the meter, so a day on which the batteries soak up the midday peak scores higher than one on which they were already full. Round-trip compares a day's discharge with that same day's charge, which means it wobbles on days that start or end with a half-full battery and only settles down when you look at a longer stretch.
