Home Assistant Energy Dashboards: Turn Smart Plug Data Into Real Savings
When our electricity bill jumped by nearly 40% in a single quarter, we did what most UK households do: we stared at the smart meter in-home display, shrugged, and carried on. The IHD told us the total spend, but it couldn’t tell us why the number was climbing. Was it the tumble dryer? The ageing fridge? The kids’ gaming PCs running all night? We had no idea. So we started experimenting with Home Assistant, a smart plug or two, and a Hildebrand Glow integration pulling data from our SMETS2 meter. Within a month we’d cut roughly £18 off a typical month by finding standby loads we didn’t know existed. This guide walks through exactly how we built our dashboards, what worked, and what we’d do differently.
Why Home Assistant Is the Best Hub for Energy Monitoring
Home Assistant is free, open-source, and runs locally on a Raspberry Pi or mini PC in our hallway cupboard. Unlike the proprietary apps that ship with smart plugs, it doesn’t silo data. We can pull readings from TP-Link Kasa smart plugs in the kitchen, Shelly smart plugs in the office, and our UK smart meter via Hildebrand Glow, then combine them into a single dashboard. That aggregation is the whole point: per-device data is interesting, but the sum across the house is what changes behaviour.
Local control vs cloud dependence
Most smart plug apps phone home to a cloud server. If the vendor’s servers go down, or the company folds, our automations stop working. Home Assistant runs everything on our own hardware. TP-Link Kasa plugs can be controlled locally via the integration, Shelly devices expose a local HTTP API, and Tasmota-flashed plugs never touch the internet at all. For energy monitoring specifically, local polling means we get consistent readings even when the broadband drops for an hour.
Supported smart plug brands (TP-Link Kasa, Shelly, Tasmota)
We’ve tested three families of smart plugs and each has trade-offs:
- TP-Link Kasa smart plugs — cheap, widely available in the UK, and the KP115 and P110 models include energy monitoring. The official Home Assistant integration is solid and works locally once set up.
- Shelly smart plugs — the Shelly Plus Plug UK has excellent power reporting granularity and a local API. Slightly more expensive but far more reliable for automation triggers.
- Tasmota — flashed onto generic plugs (often Gosund or Nous devices). Fully local, no cloud, but you need to be comfortable with flashing firmware. We use these for less critical loads.
Connecting to UK smart meters via Hildebrand Glow and Zigbee
Our SMETS2 meter talks to the national smart meter network, and the Hildebrand Glow integration (via the Glow CAD or the Bright app) exposes that data to Home Assistant. This gives us whole-house electricity and gas consumption in near real time, without needing a CT clamp. For Zigbee-based setups, some users connect a Zigbee coordinator to read directly from the meter’s Zigbee Smart Energy profile, but we found the Hildebrand route simpler and more reliable. Note that SMETS1 meters often need a firmware upgrade before they’ll work with third-party integrations.
Setting Up Your First Energy Dashboard
The setup is more straightforward than it looks. Home Assistant has a built-in Energy integration that handles most of the heavy lifting, and we had our first dashboard running in about 45 minutes.
Adding smart plugs to Home Assistant
We added each smart plug through Settings → Devices & Services. For TP-Link Kasa, the integration auto-discovers devices on the local network. For Shelly, we entered the device IP. Once added, each plug exposes sensors like sensor.kitchen_kettle_power and sensor.kitchen_kettle_energy. The energy sensor (cumulative kWh) is what the Energy dashboard needs, not the real-time wattage sensor.
Configuring the Energy dashboard for gas and electricity
Under Settings → Dashboards → Energy, we added two sources: grid consumption from the Hildebrand Glow electricity sensor, and gas consumption from the corresponding gas sensor. We also entered our tariff rates manually (more on Octopus Agile below). The dashboard then calculates daily, weekly, and monthly costs automatically, splitting usage into peak and off-peak if we’ve configured time-of-use rates.
Using the ‘Individual devices’ section for per-appliance tracking
This is where smart plugs earn their keep. In the Energy dashboard configuration, we added each plug’s cumulative energy sensor as an individual device. The dashboard then shows a breakdown of which appliance consumed what, alongside the whole-house total from the meter. The gap between the sum of individual devices and the meter total is itself useful: it tells us how much is being drawn by things we haven’t plugged into monitors.
Must-Have Cards and Customisations for Energy Data
Once the data is flowing, the default dashboard is fine but limited. We layered in a few cards that made the numbers genuinely actionable.
Built-in Energy cards vs custom cards
The built-in Energy Distribution card shows a pie-style breakdown of consumption by device, and the Energy Sources card tracks grid vs solar. They’re good for a quick glance. For deeper analysis we use ApexCharts to plot historical trends, and the Sankey chart card to visualise energy flow from grid to individual appliances. The Sankey diagram in particular made it obvious that our tumble dryer was consuming more than everything else combined during winter.
Creating a demand response automation with smart plugs
We use mini-graph-card for real-time smart plug wattage on a secondary dashboard, which is handy for spotting a device that’s been left on. But the more powerful use is automation. When our Octopus Agile prices spike above a threshold, an automation turns off non-essential smart plugs (the dehumidifier, the spare fridge in the garage) and sends a notification. This is demand response in miniature: we shift load away from peak periods and get paid for it through the tariff.
Visualising cost with the Octopus Energy integration
The Octopus Energy integration pulls half-hourly prices and consumption data directly into Home Assistant. We built a card showing the current price per kWh, the next 24 hours of rates, and our running daily cost. On Agile, prices can go negative during high wind generation, and we’ve set an automation to switch on the immersion heater when the price drops below zero. That’s a genuine saving, not a theoretical one.
Using Dashboards to Drive Energy Saving and Demand Response
A dashboard is only useful if it changes what we do. Here’s how ours drives actual behaviour.
Automating smart plugs based on real-time prices
We set up price-threshold automations for Octopus Agile: above 30p/kWh, the tumble dryer plug is disabled and we get a push notification. Below 10p/kWh, the dishwasher and washing machine plugs are enabled and we’re prompted to run a load. This is a simple form of demand response, and over a month it shifted roughly 12 kWh of usage into cheaper windows.
Setting up alerts for high standby consumption
Our biggest discovery was standby draw. An automation alerts us if any smart plug reports more than 5W for over two hours while the device is supposedly off. That’s how we found the set-top box drawing 14W continuously and the old microwave pulling 8W just to run its clock. Turning those off at the plug saved around 190 kWh a year.
Participating in demand response with Home Assistant
Octopus runs Saving Sessions and other demand response events where households are paid to reduce usage during peak windows. We built an automation that, when a session is active, turns off selected smart plugs and lowers the heat pump setpoint. The dashboard tracks our baseline versus actual usage so we can see the reduction in real time. It’s not a huge sum per event, but it stacks up over a winter.
Common Pitfalls and How We Avoided Them
We made plenty of mistakes. Here are the ones that cost us the most time.
Choosing smart plugs with power monitoring
Not all smart plugs report power. The cheapest TP-Link Kasa models (the HS100, for example) only switch; they don’t measure. We standardised on the KP115 and P110 for TP-Link, and the Shelly Plus Plug UK for anything needing fine-grained data. Buying a plug without monitoring is a false economy if energy tracking is the goal.
Managing recorder and database size
Smart plugs poll frequently. If every plug reports every second, the Home Assistant database balloons. We set the recorder to exclude high-frequency wattage sensors and keep only the cumulative energy sensors, then used a 10-day purge interval. Our database stayed under 2GB instead of growing past 10GB within a month.
Ensuring reliable smart meter data in the UK
SMETS2 meter data via Hildebrand Glow can lag by up to half an hour, and occasionally drops out if the CAD loses its connection. We added a template sensor that flags stale data (no update in 45 minutes) and sends a notification. We also kept the in-home display as a fallback for checking totals. Don’t rely solely on the integration for time-critical automations.
FAQ
Do I need a smart meter to use Home Assistant energy monitoring?
No. Smart plugs alone can give you per-appliance data and a partial whole-house picture. But a UK smart meter (SMETS2) via Hildebrand Glow gives you the full total, including hardwired loads like ovens and lighting that smart plugs can’t reach.
Will TP-Link Kasa smart plugs work with Home Assistant without the cloud?
Yes, once set up. The official integration communicates locally with the plugs, though the initial setup may require the Kasa app. After that, Home Assistant polls the devices directly on your network.
Can I use Home Assistant to participate in Octopus Agile or demand response events?
Yes. The Octopus Energy integration pulls Agile prices into Home Assistant, and you can build automations that respond to price spikes or Saving Sessions. We use smart plugs to switch off non-essential loads during peak windows.
Why is my smart meter data delayed in Home Assistant?
SMETS2 data via Hildebrand Glow typically updates every 30 minutes, and the national network can introduce further lag. If you need real-time data, add a CT clamp or use smart plugs for the devices you want to monitor closely.
What’s the best smart plug for energy monitoring in the UK?
For most households, the TP-Link Kasa KP115 or P110 offers the best balance of price and reliability. For more granular data and local control, the Shelly Plus Plug UK is excellent. Tasmota-flashed plugs are the most private option but require more setup.
Building a Home Assistant energy dashboard turned our vague anxiety about bills into a concrete list of things to fix. The smart plugs told us where the power was going, the smart meter integration gave us the whole-house total, and the automations quietly trimmed the waste. None of it required replacing appliances or spending thousands on a solar system. It just required a hub, a few plugs, and a willingness to look at the data. If you’re on a time-of-use tariff like Octopus Agile, the savings compound further, and the demand response automations mean our household is actively helping balance the grid rather than just complaining about it.