| If you are interested in recording the minute-by-minute pattern of your electricity demand but don't want to invest in a profile analyser, this DIY recorder can be cobbled together for about £40 to £70. It will record single-phase power (or power in one phase of three) up to a limit of 15 kW or so. | |
| Start with a domestic power monitor like the Electrisave Owl (right) which is the cheapest available and can be obtained for about £35 from Windtrap and other suppliers of energy-saving gadgets. Note: you could just buy a current transformer (they call it a 'sensor') on its own for about £9, or if you already have an Efergy meter, use the CT off that. |
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| Get hold of a multimeter with computer connectivity. The N56FU from Maplin Electronics is discounted to £30 until 10 June 2008 and although its PC software lacks any kind of installation or operating instructions, once you have figured it out, it works quite well. (Note: the procedure that worked for me was to plug in the meter's USB connection and allow Windows to install what it needs to install using the supplied CD, but then run setup.exe from the CD as well). |
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| All you really need from the Owl kit is the current transformer, to which you will need to connect a length of two-core cable. The CT's output is under 5V so it is quite safe. Clip the CT to the power cable near the mains supply meter (as in the normal installation) and run the two-core cable back to your PC. |
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 Connect the two-core cable to the multimeter, set the range to AC volts, start the PC software and start recording. The software allows you to save the data in a text file or spreadsheet. When you come to analyse the saved data, all you need do is multiply the recorded voltage by a factor to convert to kWh (with the Owl CT it appears to be about 130 mV per kW but that can only be approximate because it does not take mains voltage or power factor into account). |
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