🔧 Installation (zero mess)
The electrician opens the panel, takes the CT clamp, and clips it around the main supply cable (or around the heat pump cable). No cable cutting, no exposed contacts.
Energy Monitoring: Smart Meters & CT Clamps
We all dread the electricity bill. We see a huge number and start guessing: "Was it the AC? Is the heat pump consuming too much? Did someone forget the water heater?"
The guessing game is over. With a small device in your electrical panel, your phone shows live, every second, exactly where each euro goes.
1. What Are CT Clamps?
In the past, measuring current meant cutting the cable. Now we use Current Transformers (CT Clamps) - small plastic "clips" that clamp around the cable without cutting anything.
🧲 How it reads current
As current flows through the cable, it creates an invisible magnetic field around it. The "clip" reads this field and calculates with 99% accuracy how many Amps are passing at that moment.
📏 Sizes
CT Clamps come for single-phase (1 clamp) and three-phase (3 clamps, one per phase). Three-phase models (e.g. Shelly 3EM) cover an entire home's supply.
💰 Cost
A single CT clamp costs €5-15. Together with the smart meter, the full installation costs under €100 - the best investment for energy savings.
2. Smart Energy Monitors
The CT clamp connects to a Smart Energy Monitor (Shelly EM, Shelly 3EM) - matchbox-sized, clips onto the DIN rail, and joins your Wi-Fi.
📊 Live chart
Open the app (or Home Assistant) and see: "The house is currently consuming 350 W." Turn on the oven → see it spike to 2,350 W. Turn on the AC → the Inverter curve climbs smoothly then drops.
📅 History
View consumption charts by hour, day, week, month. Spot patterns: "every Sunday morning consumption spikes" - perhaps the water heater runs longer than needed.
🔔 Alerts
Set alerts: "If consumption exceeds 5 kW for more than 10 minutes, send a notification." You'll instantly know if something was left on or if a machine is malfunctioning.
🏠 Integration
The Shelly EM integrates automatically with Home Assistant, Google Home, Alexa. Its data feeds automations - e.g. "turn off the water heater if it exceeds 3 kWh today."
3. Why It's Essential for Heating (HVAC)
Air-conditioning and heating make up 60-70% of the electricity bill. Energy monitoring gives you three powerful "weapons."
🧛 Energy vampires
You switch everything off - yet the meter shows 600 W constant draw instead of 100 W (fridge + router). You've just found a forgotten pool pump or broken circulator costing hundreds of euros per year.
🔥 Heat pump health
Attach a dedicated clamp to the heat pump cable. If it runs at 100% power (4,000 W) non-stop, the heating curve is wrong or the house is leaking heat. Smooth curves at 600 W = perfectly tuned.
📉 Optimisation
By comparing consumption before and after an adjustment (e.g. changing the heating curve), you prove whether the change helped. No guessing - you measure.
📜 Real-time COP
Combine the electricity meter with a heat meter and you calculate the heat pump's COP in real time. You know exactly how many kWh of heat you get per 1 kWh of electricity.
4. The "Marriage" with Solar Panels
This is where technology "peaks". One CT clamp on the electricity you consume, one on the electricity you produce. The monitor sees both.
☀️ Free energy → hot water
"When solar panels produce 3,000 W surplus, automatically switch on the water heater to store free energy as hot water." Zero grid export, maximum self-consumption.
❄️ Free cooling
"Before sunset, fire the AC at 24 °C to cool the house with free electricity - instead of paying the utility at night." The house becomes a thermal battery.
📊 Net Metering dashboard
See live: how many kWh you produce, how many you consume, how many you export to the grid. At month's end, you know your exact energy balance - before the bill arrives.
💡 Payback
A monitor costing under €100 helps you increase self-consumption by 20-30%. That means hundreds of euros less on the electricity bill annually. Payback in a few months.
⚡ Knowledge is power - and in energy, knowledge is money. Under €100 changes your mindset: you stop guessing, instantly spot "vampires," and control your expensive HVAC machines with precision.
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