Monitoring 9 min read

Setting up consumption monitoring

P1, Shelly, or inverter CT clamps, the three routes that work in Belgium

If you have read this far in the series, you have probably grasped the central point of solar in 2026: production data without consumption data is half the picture. You can know exactly how much your panels generate. You can watch the curve dance through the day. None of it tells you whether the household is actually using that energy or sending it back to the grid for almost nothing.

Consumption monitoring closes that gap. It is also, frankly, where most installations stop short. Production data comes built into the inverter; the manufacturer hands it to you on a plate. Consumption data requires a deliberate decision and, usually, a small additional purchase. This article walks through the realistic options for monitoring household electricity consumption in 2026, with a focus on what actually works in Belgian and Dutch homes.

There are essentially three routes: read the data from your digital meter's P1 port, install a Shelly or similar energy meter in your fuse box, or use the CT clamp inputs on your inverter. Each has its place. Let me work through them.

Route 1: the P1 port on your digital meter

This is the cleanest option in Belgium and the Netherlands, and it should be the first place anyone looks. Every digital electricity meter installed in Belgium since 2019 has two user ports on the front: P1 for formatted, human-readable data once per second, and S1 for raw high-frequency samples. Dutch slimme meters (DSMR-compliant) have the same P1 port, and Luxembourg uses the same standard with the additional twist of encrypted data requiring a key.

The P1 port follows the DSMR 5.0.2 specification, which is essentially a Dutch standard that Belgium adopted with minor regional differences. What you get is everything you could possibly want: total grid import and export per tariff, instantaneous power per phase (on three-phase meters), gas consumption (delivered every 15 minutes via a wireless link from the gas meter), and the daily and monthly counters that the meter itself displays. It is the most accurate consumption data available in any home, because it is the same data your energy supplier is using to send you a bill.

There is one administrative hurdle. In Belgium, the P1 port is deactivated by default for privacy reasons and you have to ask your network operator to switch it on. Each region handles this differently:

If your meter is brand new, you can request activation during the installation visit and skip the fee. If it is older, the Fluvius web portal is the path of least resistance for Flemish households. Activation typically takes 24 to 72 hours after the request is processed.

Once the port is open, you need a small device to read it. The two popular options are the HomeWizard P1 Meter, a tiny WiFi-enabled reader that costs around €30 to €40 and exposes the data over a local API, and various DIY Raspberry Pi setups using a USB-to-RJ12 cable that you can build for around €15 in parts. Both feed cleanly into Home Assistant, where they appear as a "DSMR" or "HomeWizard" integration with detailed sensors for every value the meter publishes.

The HomeWizard option is easiest for non-technical users; the cable-and-Pi approach gives you a bit more flexibility and is well documented on Belgian blogs like Jensd's I/O buffer for those who like to tinker.

The advantage of P1-based monitoring is that it captures everything: solar export back to the grid, grid import, and the difference between them. It does not, however, see what is happening inside the house. If you want to know that the dishwasher pulled 1.8 kW between 11:23 and 12:14, you need a different tool.

Route 2: a Shelly or similar energy meter in the fuse box

For households that want more granular data, or who do not have a digital meter, the second option is to install a dedicated energy monitor in the fuse box. The most popular device in this category for European installations is the Shelly Pro 3EM, a DIN-rail mountable three-phase energy meter that costs around €130 to €170 with the included CT clamps.

The Shelly works by clipping current transformers (CT clamps) around the live wires of the circuits you want to measure. For a typical home installation, this means three clamps around the three incoming phases from the grid, giving you instant total consumption. Solar households often add a fourth measurement of the inverter's output, either by combining the data from the inverter itself (via Home Assistant) or by adding a second Shelly EM. The device measures voltage, current, active power, reactive power, and accumulated energy at 1% accuracy, with on-device storage of 60 days at one-minute resolution and Modbus, MQTT, REST and WebSocket interfaces for integration.

What you give up compared to the P1 route is total accuracy: a CT-clamp installation depends on the calibration of the clamps and is typically accurate to within 1% to 2%, where the digital meter is calibrated and certified for billing. What you gain is flexibility. You can put a Shelly EM on a single circuit (the EV charger, the heat pump, the dryer) and see exactly what it does throughout the day. You can monitor multiple buildings on the same network. You can install one in a holiday home where there is no smart meter at all.

A practical note: installing a Shelly Pro 3EM means working inside a fuse box, which in Belgium and the Netherlands is not legally something you should do yourself unless you are qualified. The device itself is straightforward to fit (DIN-rail mount, three CT clamps, three voltage references), but most insurers expect a registered electrician to do the actual installation. Expect to pay around €100 to €200 in labour on top of the device cost, depending on local rates.

For households with specific monitoring needs, separate tracking of an EV charger, a heat pump on its own circuit, a workshop with three-phase machines, Shelly devices are the right tool. For whole-house consumption, the P1 port is usually cleaner, cheaper, and less invasive.

Route 3: the inverter's own CT clamps

The third option is to use the inverter itself as the consumption sensor. Most modern inverters from Fronius, SMA, SolarEdge, GoodWe, Huawei and Enphase have an input for CT clamps or an external smart meter that lets the inverter calculate household consumption directly.

Fronius is probably the gold standard here. With a Fronius Smart Meter (around €250 to €350) installed alongside the inverter, the system reports complete household consumption to both Solar.web and any local Home Assistant integration, and the data slots cleanly into PVOutput via the Fronius push service we covered in the Getting your data into PVOutput. SolarEdge has a similar setup with their own consumption meter. SMA's "Sunny Home Manager" has been around for years and is well-supported by Home Assistant.

The advantage is that consumption monitoring is integrated with production monitoring from day one. There is no second app, no separate Shelly to set up. The downside is vendor lock-in: if you ever change inverter brands, the consumption history is part of the package you leave behind. The Shelly and P1 routes are inverter-agnostic. The inverter route is not.

This is the option I would recommend to households doing a fresh installation who do not run Home Assistant and want a single-vendor experience. For everyone else, the independent paths usually win on flexibility.

Which one for which household

A short decision tree:

Getting consumption into PVOutput

Whichever route you pick, the path to PVOutput is the same as for production data: through Home Assistant, through a Shelly or HomeWizard's MQTT output, or through a custom script. PVOutput accepts both production and consumption data on the same addstatus.jsp endpoint, so once your local pipeline is delivering both numbers, the upload is a single combined call every five minutes.

The result, when it works, is that your PVOutput dashboard shows production, consumption, the green band of self-consumption, and the gap between them in real time. The economic optimisation we discussed in the Self-consumption versus feeding back to the grid becomes visible. The dishwasher that runs at 14:00 shows up green, the one that runs at 19:00 shows up grey. Behaviour, slowly, follows the picture.

This is the moment, also, where independent apps like HelioPeak start to add real value. A production-only dashboard is informative. A combined production-and-consumption dashboard, with both numbers updating every few minutes on a phone in your pocket, is the difference between knowing and acting. We will come back to that in How HelioPeak fits into the picture in a few articles' time. For now, the data plumbing is the priority. Get it flowing, get it accurate, and the rest of the series builds on top.

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