Room By Room Audit

Once you have your monitor it is time to put it to use. Go through your house and work out what items are either continually plugged into electrical sockets or those which are irregular but frequent. These are the items you want to analyse, in order to understand the cost to you.

Here is an example of the chart that I have been preparing for my own audit. Although not every item is included, I have tried to show what the actual electricity cost is, in real terms, for common appliances in my house per month. 

Here's how to interpret the figures I have used above:

• place the monitor in the socket and click on the watts button. Then take the reading and fill in the chart with a) the usage time in hours per day and b) the usage time in days per month and c) the cost per unit of electricity. The formula is as follows: watts x hours x days x unit cost per Kilowatt hour will give you the actual cost. In Ireland, electricity costs, with recent price increases, are extremely high, at 18cent* for each kilowatt hour used, on the standard rural tariff. So, for example, an appliance using 20watts, on for 24 hours per day, 30 days a month, is calculated as :  20 x 24 x 30 / 1000 x .181 = EUR2.61. Or you get the same value by saying: 20 x 24 x 30 x .000181 = EUR2.61, by building in the Kilowatt hour into the price. That's how I have represented the values in the chart above.
  * domestic rural tariff @ 1st Aug 2008 = EUR0.1812cent, inc. vat. Source: Electricity Supply Board, issue date: 20th Aug 2008
  
  
• energy consumption for a fridge or a fridge-freezer is not constant. They use a cycling on/off system to maintain the temperature. This means that when you plug the monitor in, it may show 0 watts, then a short time later it could show 100 or more watts. So to calculate the real cost you should leave the monitor plugged in and then after a fixed time period (hour, day, week) you check the Kilowatt Hours used on the monitor rather than the watts. Then, once you have the Kilowatt hours used, you multiply this by the real unit cost. For example, I plugged my standalone  upright freezer into the monitor. After a week the Kilowatt hours read 8.37. So I can calculate the average monthly cost as 8.37 * 4.3 (weeks in a month) = 36. Then 36 x .181 = EUR6.51. But once I have calculated this, it is also possible to work out an equivalent average wattage for the appliance based on the hourly usage. So: 50watts x 24 (hrs) x 30 (days) x .000181 = EUR6.51, exactly the same figure! Or to be more precise, 100watts x 12 (hrs) x 30 (days) x .000181 = EUR6.51. So in reality my freezer, although fluctuating in wattage between 0 and 120watts, is actually using 100watts an hour, for 12 hours a day, bearing in mind the cycling on/off process. Then I add these figures to my chart.
  
  
• energy consumption for items which are constant wattage but not plugged in continuously (e.g. a kettle) can be calculated using the method above. Leave the monitor in place for a fixed time period and then work out the monthly cost from that, as we have done for the fridge-freezer above. Remember the wattage is constant, so in the chart above, the kettle is showing 2500 watts, which is correct, but it averages out to an "on" time of 0.3 hours per day (20 minutes), which then gives us the same figure as the 5 Kilowatt hours per week it showed on the energy monitor. Hopefully I have not made this too complicated!
  
  
• washing machine costs can be difficult to estimate accurately. I based the readings in the chart on a standard wash cycle, which consumed 0.6 Kilowatts. This equates to an average wattage of 800watts, based on each wash taking 45 minutes (.75 of an hour), for 20 washes per month. 
  
  
• Remember to include phantom loads. These are the items that are left in standby yet still consume electricity. That's why I have included standby figures for the TV in the lounge, alongside the TV when in use.
  
  
• don't forget to test the lighting. If you have ratings on the bulbs and these are mains voltage lights then you don't need the monitor. If they are low voltage bulbs then remember low voltage does not mean low energy! A low voltage down lighter rated at 50watts is actually using 45watts of electricity, plus perhaps another 3-4 watts for the transformer.
  
  
• It is not possible to gather real running costs of cookers and ovens, as a) these are tied directly to the fuse board and b) their high current draw means they would require specialist equipment to monitor.

I have only shown the main appliances in the chart; your situation may differ but this should give you an idea of what constitutes a large part of your electricity bill. Now, armed with the information above, we then decide what we can do to reduce the electricity requirements.