A frequently asked question: “My plug-in battery is single-phase, but my house has a three-phase connection. How are the other two phases powered, then?” Some people conclude from this that they need to buy three plug-in batteries—one per phase. That’s not necessary. The explanation lies in how your smart meter works—a principle called “internal netting”—which is separate from the net metering program that will be phased out starting in 2027.
The Misconception: A Single-Phase Battery in a Three-Phase Home
You connect a plug-in home battery to a standard outlet, and an outlet always supplies power on a single phase. Even if your home has a three-phase connection (common with higher-capacity setups, such as those with a heat pump or charging station), this doesn’t change anything: the battery itself continues to operate on that single phase.
The logical follow-up question then seems to be: who powers the other two phases? The answer is that this isn’t necessary at all, thanks to a smart meter that performs internal netting.
What is internal netting?
A three-phase smart meter measures the power on all three phases separately, but then adds them together before sending a value to your energy supplier. This is called internal offsetting, and it’s not a new feature: even the old, mechanical Ferrari meters did this.
In practical terms, this means: if your plug-in battery feeds 800 watts back into phase 1, and your washing machine is using 500 watts on phase 3 at the same time, the meter records a net feed-in of 300 watts, rather than a separate reading for each phase.
A sample calculation
- Phase 1: Battery feeds back 800 watts
- Phase 2: no consumption
- Phase 3: Washing machine consumes 500 watts
- Total reported by the meter: 800 − 500 = net 300 watts fed back
For this calculation, it doesn’t matter which phase the battery is connected to. A single plug-in battery on one phase therefore yields exactly the same result as three smaller batteries distributed across the three phases would: the meter only looks at the total.
Why this is slightly different from the net metering program
This is often where the second point of confusion arises. Internal netting and the net metering program sound the same, but they are two different things:
- Internal netting is a technical feature of the meter: it adds up the three phases. This always happens, regardless of regulations, and will not change due to the phase-out of the net metering program.
- The net metering program is the financial arrangement under which your annual feed-in is offset against your consumption at the full energy rate. This program will be phased out gradually starting in 2027
In other words: even after 2027, your meter will continue to add up the three phases as usual. What will change, however, is the compensation you receive for your net surplus feed-in. This makes self-consumption (using what you store yourself) increasingly valuable, but it has nothing to do with how many plug-in batteries you need or which phase you connect them to.
What does this mean in practical terms for your customers?
- A single plug-in battery is all you need, regardless of which phase you connect it to.
- So simply plug the battery into the nearest convenient outlet—it doesn’t have to be near a specific phase or circuit.
- This applies to both batteries and solar panels: a single-phase inverter connected to a three-phase outlet works just fine for most households and is often cheaper than a three-phase inverter.
- Only for larger solar installations (typically above 3.6–5 kW) is a three-phase inverter needed to distribute the load across the grid—but that has to do with power output, not net metering.
A rare exception to be aware of
In a small number of cases, it has been reported that a smart meter fails to correctly offset consumption against energy fed back into the grid due to a firmware error. Utility companies acknowledge this problem and usually resolve it remotely, without needing to replace the meter. If a customer is unsure whether their meter is balancing consumption and feed-in correctly, the right step is to contact the utility company—not to buy extra batteries.
Conclusion
A single single-phase plug-in home battery is sufficient, even on a three-phase connection. Thanks to internal net metering, your smart meter automatically adds up the three phases—a technical principle that is independent of the net metering program and will continue to exist even after the program is phased out. Want to learn more about the basics of plug-in home batteries? Read our explanation of what a plug-in home battery is, or check out our comparison between the Anker Solarbank Max AC and the Marstek Venus E Max.
Frequently Asked Questions About Internal Offsetting
What is internal netting?
Internal netting means that a three-phase smart meter adds up the consumption and the energy fed back into the grid across all three phases. As a result, the energy supplier receives a single net value.
Why is internal net metering different from the net metering program?
Internal netting is a technical feature of the smart meter. The net metering program is a financial arrangement under which electricity fed back into the grid is offset against consumption. The phase-out of the net metering program does not affect internal netting between the three phases.