Saturday, October 18

Why does turning the thermostat down 1 °C save money (and Carbon Dioxide)?

To many it may seem at first that turning down the thermostat on the central heating system a tad, as recommended by many government public information films, to be one of those crazy ideas with no founding in science or every day common sense. But when you consider the system as a whole (something that any eco friendly person should do) then you realise it is based on very sound science.

So where do people get the idea that it is crazy?

The reason is that people think of numbers in absolute terms from zero up. So 20°C is obviously greater than 0°C. Hence a 1°C reduction seems small in comparison, just 5% of the total. If that were how a thermostat controlled heating system worked then not much money would be saved.

But the science in that scenario is incorrect. In order to get an accurate estimation of energy saved, the 'heating system' should include the world outside your home. We must include the temperature outside the home in our calculations of energy saved.

So how do we do this?

First of all the minimum temperature possible in the home will be the same temperature that is measured outside it. So if the temperature outside is 14°C and we normally have the thermostat set to 20°C then the difference is 6°C.

In our scenario lets take the thermostat down by 1°C.

Since our temperature difference in the scenario is only 6°C, the percentage saving is now roughly 17%. This is more than triple the original perceived reduction for that particular set of circumstances. Obviously as the temperature outside the home drops further, less will be saved and if the temperature outside increases then more will be saved.

So the main defining factor is the temperature outside the home and the fact that the temperature range the central heating operates, is between the outside temperature and the thermostat setting. Since outside temperatures in the UK are not very often near 0°C, a 1°C reduction in the thermostat setting is often not as small as it seems.

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