Checking electricity consumption

Increased electricity costs and the need to conserve energy make it even more desirable to keep a check on household consumption. To do this you must read your meter and check it is functioning correctly; you will also need to know how much power different appliances in the home consume; check this on our chart.

Reading your meter

The digital type of meter is similar to a distance meter in a car; you simply read the figures from left to right. The dial type which is probably the most common, requires more attention. It comprises five black dials and one red dial. Since the red dial measures tenths of a unit it can, for this purpose, be ignored.

The black dials show from left to right 10,000, 1000, 100, 10 and single units. Each dial is read in the opposite direction to its neighbour; the 10,000 unit dial is read clockwise, the 1000 dial is read anticlockwise and so on. When the pointer of a dial is between two figures, always take the lower figure. For example, if the 100s pointer is between 1 and 2, it means that 100-plus units have been recorded. The l0s pointer will show the extra amount in 10s; if it is between 5 and 6, the number of units is 50- plus. The final figure is given by the single units dial which should always be read to the nearest unit.

By subtracting the previous week’s reading from the current one, you can see how many units you have used in a week. Multiply this figure by the unit cost (shown on your bill) and you will have the price of the electricity, excluding the standing charge and the fuel cost adjustment.

Checking your meter

On your meter is a rotating disc which revolves a certain number of times for every kWh (kilowatt-hour) or unit of electricity consumed. The number of revolutions per kWh will be marked on the face of your meter. The disc is placed so you can see only the edge on which there is a black mark. You can count the revolutions by noting the number of times the black mark comes into view.

By a simple process you can check if your meter is registering correctly. If, for example, it is marked 500 revs/kWh, a total load of I kW (for example, a one-bar electric fire or ten 100 watt lamps) will cause the disc to revolve 500 times in one hour. But there is no need for you to watch the disc for a whole hour. Switch off all the electrical equipment in the house and check the disc on the meter is stationary. Then switch on, for example, five 100 watt bulbs so you have a total test load of ½ kW. Count the number of times the black mark on the dial comes round in six minutes, using a stop-watch or a watch with a second hand for timing. Work out how many revolutions the disc should make in this time by using the following equation :

500 (revs/kWh) x ½ (kW) x 1/10 (of an hour) = 25.

Compare this figure with the number of revolutions you counted. Allowing for variations in the manufacture of the lamps used, the disc should rotate to within a couple of revolutions of the calculated figure. But before you rush off to tell the electricity company that your meter is wrong, double check there is no other equipment switched on. To do this, switch off the test load — the disc should come to a complete standstill.

If you have an hour to spare, you need not count the revolutions. Instead, you can use the sixth (red) dial which measures one tenth of a unit. Since one complete revolution equals one whole unit, just note the position of the pointer at the beginning and end of one hour. If you use a total load of lkW, the pointer of the dial should make one complete revolution.

Unit consumption of domestic appliances

Appliance – Wattage Use – Units used

  • Blanket (over) 120 All-night warmth for one week about 6
  • Blanket (under) 60 Seven evenings 1
  • Blender 200 500 pints of soup 1
  • Coffee percolator 750 About 75 cups of coffee 1
  • Cooker 12000 Cooking for family of four for one week 20
  • Dishwasher 3000 Washing a family’s dinner dishes 1
  • Extractor fan 75 12 hours’ use 1
  • Food mixer (stand model) 400 Mixing 65 cakes 1
  • Freezer (chest model) 300 One week’s running per litre of space 0.05 (per cubic foot of space) (1.4)
  • Freezer (upright model) 300 One week’s running per litre of space 0.06 (per cubic foot of space) (1.7)
  • Hair dryer 350 Three hours’ drying 1
  • Heater 2000 One hour’s heat 2
  • Immersion heater 3000 Hot water for a family of four for one week 70
  • Iron 750-1250 More than two hours’ ironing 1
  • Kettle 2500-3000 Boils about 7 litres (12 pints) water 1
  • Light (filament lamp) 100 Ten hours of light 1
  • Light (fluorescent tube) 1500mm (5ft) 80 (100W Ten hours of light (gives four times as circuit rating) much light as 100W filament lamp) 1
  • Refrigerator (table top height) 100 One day’s running 1
  • Shaver 16 1800 shaves 1
  • Spin dryer 300 Spins about five weeks’ laundry 1
  • Stereo system 100-125 Eight to ten hours listening 1
  • Television 350 Three hours’ viewing 1
  • Toaster 1000-1350 70 slices of toast 1
  • Tumble dryer 2500 One hour’s drying 2
  • Vacuum cleaner 500 Two hours’ cleaning 1
  • Washing machine (automatic) 2500 Weekly wash for a family of four 8-9 (17kg/371b) dry weight laundry
  • Washing machine (twin-tub) 2000 Weekly wash as above (one wash per fill; uses more water than automatic) 11-12
  • Waste disposal unit 250 Grinds 50kg (1 cwt) of rubbish 1

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