How to add energy monitoring to an old panel

Adding energy monitoring to an older electrical panel is one of the most valuable upgrades you can make for a local-first smart home. Unlike cloud-dependent energy monitors, the options below keep your data local, private, and controllable through Home Assistant, Hubitat, or Apple HomeKit.

The good news: you don’t need to replace your panel or hire an electrician for most solutions. Here are your real options, from easiest to most involved.

Smart Meter Integration (Easiest Path)

If you have a smart meter with a P1 port on the street side of your meter, you’re in luck. The HomeWizard P1 Meter reads your entire home’s consumption directly from your utility meter via the P1 data port. It requires zero panel work—no rewiring, no CT clamps, no electrician visits.

Setup takes about 15 minutes: connect the P1 cable to your meter, plug the receiver into power, and integrate it into Home Assistant. The device pushes data locally without cloud dependency. You’ll get whole-home consumption data accurate to what your utility bills you.

The tradeoffs: you only see total consumption, not per-circuit breakdown. If you want to know whether your HVAC or your server rack is driving your bill, you’ll need more granular options. Also, P1 availability depends on your utility—most newer smart meters have it, but older ones may not.

A complementary option for individual device monitoring is the HomeWizard Energy Socket, which tracks specific appliances but only handles devices up to its outlet rating.

Per-Circuit Monitoring with CT Clamps

For detailed breakdown by circuit, you need CT (current transformer) clamps around individual wires in your panel. This is where Shelly devices excel. The Shelly Plus 2PM and similar models support external CT clamps for power monitoring on dedicated circuits.

Installation requires opening your panel and wrapping CT clamps around the hot wires of circuits you want to track—240V circuits, HVAC, electric dryer, whatever you’re curious about. This does require working inside the panel, so if you’re not comfortable doing this yourself, hire an electrician. It’s a two-hour job for a pro.

The Shelly Plus Plug S offers simpler plug-level monitoring for devices that have outlets nearby, but it won’t give you circuit-level data. For whole-panel monitoring, look at the Shelly Wave 2PM if you prefer Z-Wave over WiFi—the Wave series uses Z-Wave Long Range for better range and reliability in panel-dense environments.

Z-Wave options from Zooz also exist—the Zooz Zen04 handles up to 15A and provides energy monitoring, but it’s limited to plug-in loads, not hardwired circuits.

When You Need Dedicated Energy Monitoring

If you want professional-grade monitoring with voltage and power factor data, the Frient Electricity Meter connects to your panel’s busbar and provides detailed metrics beyond simple wattage. It’s more expensive than CT-clamp solutions but offers更高的 accuracy for solar or generator installations.

For homes with solar, you need monitoring on both consumption and production. Most CT-clamp solutions handle this, but verify your chosen device supports bidirectional monitoring before buying.

Integration and Local Control

All these devices work locally with Home Assistant—the Shelly devices use MQTT or REST, the HomeWizard uses its own local API, and Frient uses Z-Wave. None require cloud accounts for basic functionality, though initial setup may need the manufacturer’s app.

For Hubitat users, Z-Wave devices like the Frient meter and Shelly Wave series integrate directly. Apple HomeKit support is more limited—Eve Energy offers native HomeKit energy monitoring but lacks the granular circuit-level data of CT-clamp solutions.

Bottom Line

Start with the HomeWizard P1 Meter if you want instant whole-home visibility with zero panel work. Upgrade to Shelly CT-clamp monitoring when you need per-circuit detail. Budget around $50-150 depending on how many circuits you want to track—well worth it for identifying phantom loads and optimizing your energy bill.