In Depth: Save money by tracking your electricity use
There's nothing like a steep increase in fuel costs to encourage people to start paying attention to how much power they're using in their everyday lives.
Tips on how to save energy are everywhere, but the ideal way to cut back on your power consumption is to isolate the devices using the most energy and either reduce their usage or replace them with more efficient green-rated appliances.
There are guides out there to give you average consumption figures for your electrical goods, but wouldn't it be nicer if you could see exactly how much electricity is being used as you're using it?
If this idea sounds attractive, you'll be pleased to hear that gadgets that monitor electricity usage in real-time are already on the market. We're going to be looking at one such monitor: the Current Cost meter.
This is a portable device that receives a wireless signal from a sensor on your electricity meter, allowing you to monitor your power usage wherever you are in the home. More excitingly, the unit will also allow you to download the data onto your computer thanks to the serial port at its base.
Once downloaded, it's easy to analyse your data and even share it with others using interfaces developed by the community of Current Cost users. This means you can compare – and even compete to lower – your electricity usage with that of other similar households.
We're getting a bit ahead of ourselves here. First we need to buy and set up the Current Cost meter. The unit costs £45. This may seem expensive, but if it encourages you to cut back on your electricity usage, it could pay for itself in a very short time. Some electricity companies are giving them away, so make sure that you check this out before stumping up the cash.
There are currently two versions of the meter, and this tutorial is concerned with the newer CC128 version. However, if you already have the older CC02 model, it's still possible to read its data using these methods and a little care.
Fitting the meter
The meter comes in two parts: the sensor, which fits around the mains cable leading to your home's electricity meter, and the wireless LCD display. Anyone can fit the Current Cost sensor: you just put the sensor jaws loosely around the thick round electrical wire that leads to your house from your meter (typically this is a grey wire).
If you see any burn marks or bare wires around your home meter, call in a professional electrician to check it out before installing the Current Cost device.
The sensor jaws work by using electromagnetic induction to measure the flow of electricity going through the wire. This doesn't provide an exact reading, as there are many variables to consider – the insulation on the wires, how close the clamp is to the wire and so on – but it does provide a way to monitor changes in demand, and as these are all relative, they provide a useful indication of your electricity use.
The sensor runs on batteries and sends the collected data wirelessly to the LCD display unit. On this you can see your usage measured in watts, the calculated cost per month and simple charts showing the previous day's usage, the total kWh used in the past day and month, and the temperature and time. If you tell the meter the cost of your electricity, it will also show how much you're spending.
From meter to PC
To get this data out of the display unit and onto your PC, you need a specialised USB lead. These are available from the Current Cost Ebay page (see the Resources box for the URL).
Although the port on the base of the Current Cost meter looks like a typical Ethernet socket, it won't connect to another Ethernet port. This is because it's treated as a serial connection. The Current Cost USB lead available from the Ebay store allows the connection to be seen as a virtual COM port on your computer.
The Prolific PL-2303 drivers provided support Windows 2000 and XP, Mac OS X and Linux (although some kernels include support without extra drivers).
The data is sent out in XML format every six seconds, so in principle it's easy to monitor everything in real-time. As the meter only stores a limited amount of historical data, it's much better to dump the data onto your computer instead.
To see what's in the feed, use something like HyperTerminal on Windows XP (if you're using Vista, try Putty). It will look something like this:
Each reading is sent out as a single line of XML. XML uses a similar tagging method to HTML, but where HTML tags specify how to display the data in a browser, XML defines the content.
Let's break down the Current Cost feed into its components by describing what the tags mean:
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At a longer interval (one minute past every odd hour), the unit also provides historical data measured in kWh in periods of two hours (
If you're interested in delving deeper, there's a much fuller explanation of the tags at CurrentCost.com.
Converting the data
Now we know what the data means, we can start using it to produce graphs that will allow us to interpret it.
As it's provided in a relative way – as in 'this is the electricity used two days ago' – it would be handy to get the exact date and time that the reading was taken. To convert the data we could just write a bit of code, but fortunately we don't need to; Current Cost enthusiast Dale Lane has already done this for us. This handy application is available for free.
His open-source Python script transforms XML data such as
Again, rather than us having to write our own application to handle this, Dale has already taken the process one step further and produced a graphical user interface to produce our graphs for us. All we need to do is feed the data into it direct from the Current Cost meter. Again, the code is open source and is available with some very useful guidance notes. Just download the latest version to get going.
The first time you use Dale's GUI (by unzipping the download and clicking on the '.exe' file) it will ask you where you want to store your data as a '.ccd' file. Next, you need to populate the app with your Current Cost data.
Go to 'Download history' on the toolbar and choose to download the data that you have so far ('Download once | Download via serial port') or remain connected to the serial port for real-time data ('Stay Connected | Download via serial port'). The app will prompt you to let it know which COM port it needs to connect to (you can find out which one it is on your PC by going to 'Device manager' and choosing 'Ports').
The first time that you do this, it can take quite a while to get everything downloaded, depending on how long your Current Cost meter has been collecting data – so this might be a good time to go and put your eco-friendly kettle on. The graphs will appear as soon as the download is complete.
The tabs below the toolbar allow you to toggle between the numerous different views. You can choose to view your data hourly, daily or monthly, and decide whether you want to see the live feed or an average of your daily and monthly electricity use.
Costing the earth
Aside from graphs, the data can be displayed in three ways. To swap between them, change the option ticked in the Data dropdown menu. The 'Display kWh' setting shows your electricity usage in kWh. The 'Display GBP' setting displays how much your electricity is costing you. When you choose this option, the app will prompt you to enter the cost of your electricity in pounds sterling per kWh.
This information will normally be available from your electricity bill. Finally, the 'Display CO2' setting is a simple indication of how many kg of CO2 you are producing with your energy usage. This calculation is based on data from the main electricity suppliers. You'll also notice that there is an option on the Data menu to 'Set personal target'. This lets you tell the app how much you want to spend on electricity.
After you've done this, it will add a horizontal line to your graphs. Stay below that line and you are on target to achieve your goal. If you've only just got your Current Cost meter, the graphs will look a little sparse, but once you've been collecting data for a month or so, the displays quickly let you work out a lot of useful information.
For example, you can see which appliances use the most energy by comparing the time that they were switched on with the energy consumption at that point. You can even work out the repercussions of leaving your appliances on standby instead of switching them off.
For a quick summation of your electricity usage, just click on the Trends tab. If you discover what has caused an unusually high or low reading, you can also annotate your graphs as an aide-memoire – just click on the bar in the graph that you're interested in to add a note. Each graph can be zoomed into or saved as a PNG image file by using the icons at the bottom left of the screen. You can also download the data as a CSV file by clicking on 'Export history'.
Comparing your data
The application has another trick up its sleeve: you can compare your data to that of others and let them see yours. This involves putting your data onto a publicly accessible Google web server. The process requires your Google username and password (you can set one up when you first visit if you don't already have one).
There are clearly some privacy concerns here, but Dale assures us that every effort is being made to keep the data anonymous. Once you're logged in, you can choose friends that you know are participating using the 'Manage your friends' list.
Don't know anyone else with a meter? Not a problem: the 'Manage your groups' option allows you to get data from those in a particular demographic ('two-bedroom houses' for example), allowing a fair comparison between you and them. You can even compare your data to that produced by the National Grid, which can help you to avoid using expensive peaktime electricity.
And there you have it: a simple way to get your electricity usage broken down in real-time, ready to analyse and work out how to reduce it. It's easy to get obsessive about this, though: watch out that you don't end up sitting in the dark, wincing every time someone presses the doorbell.
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