P1 meter or CT clamp: which meter does your home battery need?

Last updated: 26 September 2026 · By Team Multi-Solar, home batteries since 2022, Rotterdam

A P1 smart meter dongle (P1-meter) reads your smart meter via the P1 port and you plug it in yourself; it is the standard choice for a DSMR 5 smart meter. A CT clamp physically measures the current on the main cable in the electrical panel and is the choice if you have no P1 port or no working one; it is fitted by an installer. Which of the two your home battery needs, and whether your HomeWizard meter will also work, is explained below. At the bottom you will find a five-step decision tree.

What is the difference in one table?

P1 meter (from us: Marstek CT003) CT clamp (from us: Marstek CT002 kWh meter)
What it measures Reads the meter readings and the current power from your smart meter Measures the current through the main cable with a current clamp (current transformer)
Where it is connected In the P1 port of the smart meter, with USB-C power supply On a DIN rail in the consumer unit, clamps around the phase wires
Who connects it You, in a few minutes A qualified installer, via a quote
Measuring interval DSMR 5: every second; DSMR 4: every ten seconds Continuous, independent of the smart meter
Per phase No, the total of the connection Yes, per phase (CT002: three-phase, up to 100 A per phase)
Works without a smart meter No Yes
Which batteries Marstek Venus E, A, D, Max and X; comparable P1 meters from Zendure, Anker and HYXi Marstek batteries; per-phase meters for fixed systems (Sigen Sensor, Shelly Pro 3EM)

Why does your battery need a meter?

A home battery only does one thing smartly: charging when your home has surplus electricity and supplying when your home is short of electricity. To know that, it has to see what is happening at the electrical panel. Without measurement, it charges and discharges blindly, on a time schedule, and may export to the grid while you are drawing electricity yourself. With a meter, the “zero export” mode works: the battery fills exactly the gap between generation and consumption, up to 800 W via the socket. You can read whether a plug-in home battery or a fixed system suits you in plug-in or fixed.

What is a P1 meter and how does the P1 port work?

The P1 port of your smart meter

Every smart meter in the Netherlands has a P1 port on the front: an RJ12 connection through which the meter sends its data out. It is a read-out port. You cannot change any settings on the meter with it, and you do not need to register anything for it. The CT003 P1 meter is a small box that fits into that port, is powered via USB-C and passes the data on to the battery via Wi-Fi.

DSMR 4 or DSMR 5: check your meter

The P1 standard of Netbeheer Nederland determines how often the meter sends its data. With DSMR 5, that is every second; with DSMR 4, every ten seconds. For a battery, that difference is significant: with an interval of ten seconds, it responds slowly to a washing machine switching on, and in the meantime supplies too much or too little. Marstek therefore requires a DSMR 5.0 or higher meter for the CT003. If you have an older meter, Marstek prescribes the CT002 kWh meter, fitted by a professional installer. The type is stated on your meter; meters installed after around 2017 are almost always DSMR 5. The CT003 works with the common SMR 5 meters from Sagemcom, Iskra, Kaifa and Landis+Gyr.

Connect it yourself in five minutes

  1. Plug the P1 meter into the P1 port of your smart meter.
  2. Connect a USB-C cable with a 5 volt adapter; a higher voltage can damage the meter.
  3. Make sure you have good Wi-Fi at the electrical panel and have your network name and password ready. The meter only works on 2.4 GHz.
  4. Open the Marstek app, choose “Add device”, select the meter via Bluetooth and under “Meter selection” choose the brand and type of your smart meter.
  5. Then pair the battery with this meter. With a three-phase connection, switch on the “three-phase sum” mode; see single-phase or three-phase.

What is a CT clamp, and what is the CT002?

How a current clamp measures

A CT clamp (current transformer) is a ring that clamps around a phase wire and measures the current flowing through it, without interrupting the wire. If you measure all three phases, the system knows per phase whether electricity is coming in or going out. The Marstek CT002 is a three-phase kWh meter on a DIN rail with such clamps, up to 100 A per phase and with an accuracy of 1 percent. So it does not sit in the P1 port, but in the consumer unit.

When do you need a CT clamp?

  • You do not have a smart meter, or your meter has no working P1 port.
  • Your meter is DSMR 4 or older, in which case Marstek prescribes the CT002.
  • You have a three-phase connection with heavy consumers and want to measure and control per phase.
  • You have multiple batteries and want a measurement that does not depend on the P1 port.

Who may connect it?

A CT clamp goes behind the main switch, where the electricity comes in. Work there is reserved for a qualified installer, in accordance with the Dutch installation standard NEN 1010. Marstek also prescribes this. With us, this is done via a quote; you can buy the CT002 separately among the battery accessories or as a variant with the battery.

Will a HomeWizard, Shelly or other P1 meter work too?

Often yes, with one important limitation. Marstek supports pairing external meters such as the HomeWizard P1 meter and the Shelly Pro 3EM, but only if you use a single battery. With two or more Marstek batteries, a CT002 or CT003 is mandatory for stable operation. Conditions: the external meter is on the same Wi-Fi network as the battery, and with HomeWizard the “Local API” is switched on in the HomeWizard Energy app. You pair it in the Marstek app under the CT settings, using the IP address of the HomeWizard meter.

Per model in our range:

  • Marstek Venus E 3.0 and Venus A: you choose the P1 meter (CT003) or kWh meter (CT002) when ordering; if you already have one, you can order without. Venus D and Venus Max: CT003 P1 meter (supplied as standard) or CT002. HomeWizard or Shelly only with a single battery.
  • Marstek Venus E 4.0: P1 meter or CT clamp as an option.
  • Marstek Venus X (fixed): controlled via CT003, CT002 or the Shelly Pro 3EM.
  • Zendure SolarFlow: Zendure's own P1 meter or a Shelly Pro kWh meter in the electrical panel, selectable when ordering.
  • Anker SOLIX and HYXi HALO: the brand's own P1 meter, supplied as standard with HYXi.
  • Sigenergy and Enphase (fixed): the installer fits the system meter, the Sigen Sensor for Sigenergy, the IQ Gateway Metered for Enphase.

In short: if you already have a HomeWizard, you can order the Marstek Venus E 3.0 in the “without meter” variant, as long as you stick to a single battery. If you want to expand, choose the variant with a P1 meter straight away.

P1 port already in use: splitter or not?

If a HomeWizard, charging point or energy display is already plugged into your P1 port, there are three routes.

  1. Let the battery be controlled via the existing meter. With one Marstek battery and a HomeWizard, that is the simplest solution: no extra box.
  2. Use a P1 splitter. An active splitter divides the signal between two devices. Marstek notes that with the Landis+Gyr E350 and E360, an active splitter is needed anyway in nine out of ten cases, because these meters transmit their data differently; Marstek recommends the active splitter from HomeWizard.
  3. Choose the CT clamp. Then the battery no longer needs the P1 port.

In practice, we see that some combinations drop out or control unevenly via a splitter. If that happens, use one meter for the battery and contact our customer service for the right setting.

Which meter do you choose? Five-step decision tree

  1. Smart meter with P1 port, DSMR 5, one battery: choose the P1 meter (CT003). You can plug it in yourself.
  2. P1 port already in use: let the battery be controlled via your HomeWizard (only with one battery) or fit an active splitter.
  3. No P1 port, old meter or faulty port: choose the CT clamp (CT002), connected by an installer via a quote.
  4. Three-phase connection and want to control per phase, or multiple batteries: choose the CT002 or, with a fixed battery, a three-phase meter such as the Shelly Pro 3EM.
  5. Fixed home battery: the installer determines the measurement in the quote; the system meter is included in the package.

Frequently asked questions

Can I use my HomeWizard P1 meter for my home battery?

With Marstek, yes, as long as you have one battery and the Local API is switched on in the HomeWizard app. With two or more batteries, Marstek prescribes its own CT003 or CT002.

Do I need a P1 splitter if the P1 port is already in use?

Only if both devices want to read the port directly. If the battery can be controlled via your existing meter, then no. With a Landis+Gyr E350 or E360, according to Marstek an active splitter is usually needed anyway.

May I connect a CT clamp in the electrical panel myself?

No. The clamps go behind the main switch, and that work is for a qualified installer. You may plug in a P1 meter yourself.

Does a home battery work without a smart meter?

Yes, with a CT clamp. It measures the current itself and does not need the P1 port. Without any meter at all, the battery only works on a time schedule, and that rarely makes sense.

Does a P1 meter measure per phase with a three-phase connection?

No, the P1 meter passes on the total of your connection. For most plug-in home batteries that is enough: in the “three-phase sum” mode, the battery is controlled based on that total. If you want to measure per phase, choose the CT002 or a three-phase meter.

Order your Marstek Venus E 3.0 with a P1 meter, with a CT clamp or without a meter; you make the choice on the product page. All plug & play home batteries are grouped together, as are the fixed home batteries, for which you request a quote. You will find the complete overview under home batteries; the fixed battery with the most meter options is the Marstek Venus X.

Sources

  • Marstek Netherlands, “Installation manual Marstek P1 meter, home battery & app” (June 2026): smart meter requirements, CT003 installation, external meters and splitters, three-phase sum mode
  • Netbeheer Nederland, DSMR 5.0.2 P1 companion standard and DSMR 4.2.2 P1 (consulted 26 September 2026): measuring interval of one second and ten seconds respectively
  • Product data for Marstek CT003 and CT002, Venus E 3.0, Venus E 4.0, Venus A and Venus X, Zendure SolarFlow, Anker SOLIX, HYXi HALO, Sigenergy and Enphase: manufacturer documentation and product pages on multi-solar.nl (26 September 2026)
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