Energy monitors provide a real-time display of your electricity consumption. They are a cost-effective way to track an entire home or businesses energy cost and power usage trends.
They are referred to as Household Power Monitors, Home Energy Monitors, Electricity Usage Monitors, or In-Home Displays (IHDs).
We refer to them as Wireless Energy Monitors because they track readings wirelessly. This distinguishes them from power meters which are usually plug-in or hard-wired devices.
How does a Home Energy Monitor work?
Generally speaking, all wireless home electricity monitors have three main components:
1) Electricity Usage Sensor
This is the device that measures electricity consumption. They are typically a current transformer (CT) clamp, optical sensor or magnetometer.
CT Sensor Clamps work by measuring the electromagnetic field around a power cable. They're like a 'clamp meter' that you may have seen an electrician use. As such, they are an ideal non-invasive way to monitor residential energy usage. They clamp around (not on!) the main supply cable or sub-circuit wires in your electricity meter board. The Efergy Elite uses this system as do previous models, including Efergy Engage, Watts Clever EW4008 & EW4009, and Current Cost EnviR.
Note: Clamping a CT sensor around a regular white extension lead will read '0'. This is because the magnetic field from the active and neutral wires cancel each other out. For monitoring individual appliances, we recommend a plug-in power meter.
Optical Sensors work by measuring the pulse output on your utility meter or kWh sub-meter. The pulse output is quite simply a red LED light that flashes in sync with your power usage. Some optical sensors can even measure old-fashioned 'spinning disk' mechanical electricity meters. This technique is deployed by the Powerpal and previously by the Watts Clever EW4030.
Magnetometers are only used, as far as we know, by Powersensor. The word 'magnetometer' became a little more widely known when Apple recently introduced one to 'line up' wireless chargers with the back of the iPhone. They are similar to CT clamps in that they measure the electromagnetic field near a conductor. But they are even easier to install because they don't even need to clamp around a power cable, they just need to be near it.
2) Transmitter
The energy sensor plugs into (or is part of) a transmitter which usually sits inside the switchboard. The job of the transmitter is to transmit data from the sensor to a receiver located elsewhere. Home energy monitor transmitters use a variety of methods to send the data, including:
Bluetooth or Zigbee - both fairly short range but suitable for many applications. Zigbee is often transmitted by your utility's smart meter. But tapping into an existing Zigbee signal is near impossible without the right hardware.
433MHz - similar frequency used by some remotes, weather stations, and other devices. Can send data up to about 70m best case.
Wifi - another option that has a wireless range between the two above options.
Electricity monitor transmitters are typically battery-powered devices.
3) Receiver, Display or Gateway
The receiver can be a display screen, your internet router, a separate 'hub', or even your mobile phone. Sometimes the receiver is just an internet 'gateway' which allows you to view the data elsewhere (such as on your computer, tablet, or mobile phone app). Receivers can be plug-in devices or battery powered.
Put the three together (sensor + transmitter + receiver) and you have an energy monitoring system!
Popular Uses of Energy Monitoring Systems
Some of the most common motivations for installing an electricity usage monitor are:
Keep track of your residential or business energy usagebefore you get stung with a high power bill.
Make the best use of solar power generated on-site with solar PV panels.
Educate your family (or work colleagues) about how much you spend on electricity.
Find out what your standby, after-hours, and/or overnight energy usage is.
Find out if the power company is ripping you off!
Uncover the usage of your air conditioning, electric hot water, lighting, and more.
Facilitate behaviour change to substantially reduce energy consumption.
Help reduce your dependence on fossil fuels and lighten your carbon footprint.
Note: If you want to on-bill a tenant for power usage we recommend an electricity sub meter. Home energy monitors are excellent educational tools, but they are generally not used as metering devices.
