The OWL Electricity Monitor



The OWL Electricity Monitor shows the cost of the electricity that you use - as you use it.

Boil an electric kettle and you see the cost of your consumption rise; switch off a fan heater and you see the cost fall.

Awareness of how much electricity is being used is a powerful incentive to managing consumption and, therefore, your costs.

Background Consumption

Once an OWL is installed it soon becomes clear that electricity is being consumed ‘in the background’, ie with little or no human intervention. This includes the electricity used by refrigerators, central heating systems, televisions on stand-by, trickle chargers etc. In fact it is very difficult to consume no electricity. Only a power cut seems to be able to reduce our consumption to ‘Nil’.

Nevertheless, it is a good idea to find out just what your background cost is. For example, looking at my OWL (2pm, 3rd February, no central heating on) my background costs are 4.5p per hour, which sounds modest but is equivalent to around £400 per year, a significant percentage of my annual electricity bill. When the (gas) central heating comes on at 4.30pm, and a few lights are switched on, the rate will rise to about 5.5p per hour, equivalent to around £500 per year.

In practice I can do little about my energy-efficient refrigerators, but I can do something about my gas-fired central heating system if I choose to run it for shorter hours (coupled with bursts from a fan heater in the room I am working in) and/or settle for a lower thermostat temperature (coupled with warmer clothing of course) – and you may have more items on stand-by and trickle charge than you think. It is a matter of managing one’s life-style – not of abandoning it.

Your cost of background electricity will differ from mine, but it is certain to be a significant part of your total bill, and worthy of your attention.

Discretionary Consumption

Some examples:

  • My electric kettle costs about 2.5p per minute, depending on how much water I boil; the microwave oven costs about 1.5p per minute.
  • My R80 spotlights cost about 1p per hour; the florescent strip lights about 0.3p per hour; the energy-efficient lamps about 0.2p per hour.
  • The computer costs about 9p per 24-hour day, unless I switch the printer on, when it goes up to 22p per day. etc etc.

OWL Costs and Savings

It is, of course, difficult to remember all the various consumption costs, but equally it is astonishing how a little knowledge (even if it is a dangerous thing) leads to quite significant changes to long-ingrained habits.

The OWL is a portable, neat device about 12cm high by 11cm wide and 3cm deep. It is simple to instal without the need for an electrician The cost, and cumulative cost, of electricity being consumed, together with room temperature, are clearly displayed … and it is a WHICH ‘Best Buy’. Our OWL (model CM119) cost £35, but it paid for itself within twelve months.

There is also a smaller, and cheaper, OWL MICRO (model CM130), which costs £25, but this model does not display cumulative cost or room temperature.


Without in any way inconveniencing ourselves, we now

  • are aware of the cost of what we are doing
  • use doors to regulate heat flow. For example, in winter if there is sun on the conservatory, its door is left open (and vice-versa) – similarly with a heated kitchen. Even the heat from a desktop computer will keep the chill off a small room with a closed door
  • use spot heating / closed doors where we work (outside central heating times)
  • are aware of room temperatures (the OWL itself shows temperature, and simple thermometers are cheap and unobtrusive). The reaction to ‘I’m feeling cold’ is to check the room temperature before switching on a heat source. If the room temperature is OK, the solution is warmer clothing (and/or see a doctor)
  • use, wherever practicable, low-energy bulbs and switch off unnecessary lights before bedtime
  • etc etc

How one makes use of the information from an OWL is a matter of judgement, a trade-off between cost and inconvenience. For example, my television consumes 2 watts on standby – too little to worry about – but when on, it consumes over 100 watts – so I switch it off more often than I used to.

More information about the OWLs is given on its website, or is available from:

2 Save Energy Ltd. The Annexe, Field House Barn, Chineham Lane, Sherborne St John, Basingstoke, Hampshire RG24 9LR. Tel: 01256 383 430

Should you wish to have more information from the writer of this Case Study please

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