Energy Debt

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I’ve worked in sustainability for a number of years, so I’m very familiar with the difference between a kilowatt and a kilowatt-hour* but a lot of people have little understanding of energy, and don’t know how much they should be using.

A very simple way to improve your energy literacy is to take meter readings regularly (I do mine weekly and monthly). This can help in two very useful ways. Firstly, you can say goodbye to estimated bills, which may be overcharging you (they may undercharge you too, but it will always catch up with you in the end). Secondly, you can start to predict how much you are going to spend each month and put some money aside for it.

Here’s a quick guide:

See this page for pictures of the different meter types.


Your gas meter will either be in cubic metres (m3) or cubic feet, and it should say on the meter. These units are then be converted into kWh.

For meters in cubic metres (m3):

  • Meter reading 1: 12345
  • Meter reading 2: 13345
  • Consumption (m3) = 13445 – 12345 = 1000 m3
  • Consumption (kWh) = 1000 x 11.2 = 11200 kWh
  • Cost (£) = 11200 x 0.041 (1 kWh gas costs 4.1p) = £459.20

For meters in cubic feet:

  • Meter reading 1: 1234
  • Meter reading 2: 1334
  • Consumption (m3) = 1344 – 1234 = 100 m3
  • Consumption (kWh) = 100 x 31.7 = 3170 kWh
  • Cost (£) = 3170 x 0.041 (1 kWh gas costs about 4.1p) = £129.97


Your electricity meter will be either one figure, or two if you are on Economy 7 tariff. The numbers are in kWh so there’s no need to convert. If you have Economy 7, simply record both numbers and add the consumption together.

  • Meter reading 1: 1111
  • Meter reading 2: 1211
  • Consumption (kWh) = 1211 – 1111 = 100 kWh
  • Cost (£) = 100 x 0.14 (1kWh electricity costs about 14p) = £14.00

The longer you keep taking meter readings, the more comfortable you will become with the calculations and it will be easier to predict how much money you need to put aside for the bills.

Of course, many people can’t afford their bills even if they are calculated correctly. The only real solution is to reduce consumption either by turning things off or by having better insulation. More on that in another post though.

*for those who don’t know, 1 kW is the power of an appliance, and 1 kWh is an amount of energy consumed. A good analogy is a tap; a dribble of water coming out is low power (kW), the tap opened full is high power (kW). The total amount that comes out when the tap is on (e.g. a bath-full) is equivalent to the consumption (kWh)