Smart Home Energy Monitoring: Track Every Watt in Your House

I thought I had a pretty good handle on my electricity usage. I had LED bulbs everywhere, ran the dishwasher at night, and kept the thermostat at reasonable temperatures. Then I installed a whole-home energy monitor and discovered that my 15-year-old chest freezer in the garage was using more electricity than my refrigerator, dishwasher, and washing machine combined. It was pulling over 150 kWh per month — about $20 worth of electricity — because the compressor was running almost continuously. Replacing it with a new Energy Star model cut that to under 30 kWh per month.

That single discovery paid for the energy monitor in less than two months. And it is not an unusual story. Most people have at least one or two energy vampires hiding in their home that they do not know about.

Whole-Home Energy Monitors

These devices install at your electrical panel and measure the power flowing through your circuits. They give you a real-time view of your entire home energy consumption, and the better ones can break it down by individual circuit.

Emporia Vue 2 (~$90 for the 16-circuit bundle) — This is the best value in home energy monitoring by a wide margin. The base unit clamps onto your two main power lines and measures total home consumption. The 16-circuit expansion pack adds individual CT (current transformer) clamps that you put on specific circuit breakers to monitor them independently. So you can see exactly how much your HVAC is using, how much goes to the kitchen circuit, what the dryer pulls, and so on.

Installation requires opening your electrical panel, which makes some people nervous. The CT clamps just clip around the wires — you do not make any electrical connections or touch any terminals. Still, if you are not comfortable working around a live panel, hire an electrician for an hour. The Emporia connects to WiFi and streams data to their cloud app, where you can see real-time usage, historical trends, and estimated costs. It also integrates with Home Assistant through a community integration.

The one downside: Emporia is cloud-dependent. If their servers go down or they shut down the service, the hardware becomes useless. For $90, I think the risk is acceptable, but it is worth knowing.

Sense Energy Monitor (~$300) — Sense takes a different approach. Instead of per-circuit monitoring with CT clamps, it uses machine learning to identify individual devices by their electrical signatures. It clips onto your main power lines and over the course of several weeks, it learns to recognize your refrigerator, HVAC, oven, washing machine, and other devices by the unique electrical patterns they create when they turn on and off.

When it works, it is genuinely magical. The app shows you a real-time bubble chart of exactly which devices are running and how much each one is drawing. The problem is that it does not always work. Device detection is inconsistent and can take weeks or months to identify some devices. Resistive loads (space heaters, hair dryers, ovens) are easy for it. Variable-speed motors and modern inverter-driven appliances are harder. Some devices never get identified at all.

Sense also offers solar monitoring if you have solar panels, and it has a dedicated Alexa skill, Google integration, and a Home Assistant integration. At $300, it is a significant investment, and I would only recommend it if you want the per-device detection magic and are okay with it being imperfect.

IoTaWatt (~$270 for base + 7 CT clamps) — This is the enthusiast pick. IoTaWatt is an open-source energy monitor that stores all data locally — no cloud dependency whatsoever. It runs a local web interface, logs data to InfluxDB, and integrates beautifully with Home Assistant. You buy the base unit and as many CT clamps as you need (up to 14 inputs). The hardware is solid and the community is active.

The tradeoff is that there is no polished consumer app. You are working with a web interface and Home Assistant dashboards. Setup is more involved than Emporia or Sense. But if you want a local-first, privacy-respecting, no-subscription energy monitor that you fully control, IoTaWatt is the way to go.

Smart Plug Energy Monitoring

If you are not ready to open your electrical panel, smart plugs with built-in energy monitoring are a great starting point. Plug them into individual devices and see exactly what each one draws.

TP-Link Kasa KP115 (~$15) — My favorite energy monitoring smart plug. It tracks real-time wattage, voltage, current, and cumulative energy usage over time. The Kasa app shows daily, weekly, and monthly usage graphs. It works with Alexa and Google, and the Home Assistant TP-Link integration provides all the energy data as sensors. Build quality is solid and WiFi connection is reliable. One important note: the KP115 is rated for 15 amps, so it handles most household devices but is not suitable for high-draw appliances like space heaters or window AC units.

Shelly Plug S (~$18) — If you want local control without cloud dependency, the Shelly Plug S is excellent. It runs a local web interface, supports MQTT, and integrates natively with Home Assistant. Energy monitoring is accurate and the data stays on your local network. Shelly also supports their own cloud if you want remote access. The plug is compact, which is nice — it does not block adjacent outlets like some bulkier plugs do. Rated for 12 amps.

Setting Up the Home Assistant Energy Dashboard

Home Assistant added a dedicated Energy Dashboard in 2021, and it has become one of the platform's best features. Here is how to set it up:

Step 1: Add your energy sources. Go to Settings > Dashboards > Energy. Under "Electricity grid," add the sensor entity from your energy monitor that tracks total home consumption. This should be a sensor that reports cumulative energy in kWh (not watts — there is an important difference). If you have solar panels, add your solar production sensor under "Solar panels."

Step 2: Add individual devices. Under "Individual devices," add the energy sensors from your smart plugs. Each one will show up as its own entry on the dashboard, so you can see how much each monitored device contributes to your total.

Step 3: Configure your electricity rate. Under "Grid consumption," set your electricity price. If you have a flat rate, just enter the per-kWh cost. If you are on a time-of-use plan, you can set different rates for peak, off-peak, and shoulder periods. This turns all the energy data into actual dollar amounts, which is way more motivating than abstract kWh numbers.

Step 4: Wait for data. The Energy Dashboard needs at least a few hours of data before it starts showing useful graphs. Give it a full day or two before you judge it. Over time, it builds up daily, weekly, and monthly comparisons that let you spot trends and anomalies.

Identifying Energy Vampires

Once you have monitoring in place, here are the most common energy vampires I see people discover:

• Old refrigerators and freezers — Anything more than 12-15 years old is probably using 2-3x what a modern unit would. That second fridge in the garage is often the single biggest energy waster in a home.
• Desktop computers left on 24/7 — A gaming PC with a high-end GPU can draw 100-200W at idle. That is $100-200 per year just sitting there doing nothing. Put it to sleep.
• Set-top boxes and game consoles — Cable boxes are notorious for drawing nearly the same power whether you are watching TV or not. An Xbox Series X draws about 13W in "instant on" standby mode. Put it in energy saver mode.
• Old plasma TVs — If you still have a plasma TV, it is probably drawing 200-400W while in use. Modern OLEDs and LEDs use a fraction of that.
• Dehumidifiers — These run constantly in basements and can easily use 500-800 kWh per year. Make sure yours is Energy Star rated and appropriately sized for the space.

Time-of-Use Optimization

If your utility offers time-of-use rates (and many are moving in that direction), energy monitoring becomes even more valuable. You can see exactly how much power you are consuming during expensive peak hours versus cheap off-peak hours, and shift loads accordingly.

Smart plugs let you automate this. Schedule your EV charger, pool pump, or dehumidifier to run only during off-peak hours. Use Home Assistant automations to shift non-time-sensitive loads automatically based on your rate schedule. Even simple changes — running the dishwasher at 9 PM instead of 7 PM — can save meaningful money if the rate differential is large enough.

Solar Monitoring

If you have solar panels, whole-home energy monitoring is almost mandatory. You want to see not just how much your panels produce, but how much you are consuming simultaneously, how much you are exporting to the grid, and how much you are importing. The Emporia Vue 2, Sense, and IoTaWatt all support solar monitoring with additional CT clamps on your solar circuit breaker.

The Home Assistant Energy Dashboard handles solar beautifully, showing production vs consumption in real-time and calculating your self-consumption percentage. This data helps you decide when to run heavy loads (do laundry when the sun is shining) and evaluate whether adding a battery makes financial sense for your usage pattern.

Start Small, Learn a Lot

You do not need to go all-in on day one. Start with a couple of smart plugs on the devices you are curious about. See what surprises you. Then consider a whole-home monitor when you want the full picture. The data alone changes your behavior — once you can see the cost of leaving something running, you naturally start being more intentional about it. I have cut my electricity bill by about 12% since I started monitoring, and most of that came from just three changes I would never have made without the data to guide me.