2 Taking action – energy management systems

2.1 The need to monitor energy use

In this section we look almost entirely at energy, as it is the main contributor to CO₂ emissions, either directly (through burning fuels on site or in vehicles) or indirectly (through purchasing electricity, heat or steam that has come from fossil-fuel sources).

‘If you don’t measure it, you can’t manage it’ sums up the first stage of good energy management – as a prerequisite you need to monitor and report energy consumption on a regular and timely basis. This is not quite the same as calculating your carbon footprint – that may be done on an annual basis; energy needs to be monitored monthly, weekly or daily (or per batch of product) if it is to be effectively controlled. This process is known as monitoring and targeting (M&T). Plotting energy use on a regular time series allows small variations in demand to be seen more clearly – and a cusum (cumulative sum of differences) chart can be used to plot variations against average consumption, normalised for production volumes or temperature differences.

You can see some real-life examples of cusum charts in this slide show.