Building Energy Management: Monitoring

MONITOR

The first step of building energy management (after you’ve decided you are going to do it and are committed to it!) is energy monitoring. Why monitor energy use? Well, you need to understand what amounts of energy are being used where before you can effectively think about how to reduce that. Of course the way a building uses energy changes over time – between weekdays and weekends, over the holidays, with changes in the weather and with changes in use.

Energy needs to be monitored over time to account for this – which is why SMEasure recommends weekly meter readings. Weekly meter readings increase the power of analysis and benchmarking procedures. However, you will still get some benefit from fortnightly or monthly readings. Follow the links to get help with reading gas and electricity meters.

Once you understand how much energy is used, you can begin to think about what is driving this usage. This involves analysing the energy use you have monitored. SMEasure helps in this process by doing some analysis for you through:
• taking account of your building type and occupancy;
• giving you graphs to help you understand what might be driving your energy use;
• factoring in the weather conditions;
• giving you energy ratings to help you benchmark and track improvements.

Monitoring and analysing energy use involves a number of steps. The links below break this down into manageable chunks, taking you through the different elements of what SMEasure can do for you.

• The largest user of energy is often heating. Heating in a building will be influenced by the outside temperature – defined as ‘degree days’. Why this needs to be taken into account in analysis is explained through ‘what is the value of degree days for building energy management?’.

• One of the graphs that SMEasure gives you once you have taken a few readings is a performance chart which shows you the relationship between your building’s heating energy (i.e. gas) use and the outside temperature. Three parts of this chart are particularly important – the slope, its R-value and where the line crosses the graph’s y-axis. Generally this chart is useful for showing you the quality of your building fabric (i.e. how well it keeps the heat in), how well the heating controls are working and the amount of gas used for non-heating uses.

• A second graph you get is called a control chart. The control chart shows you when heating energy use is higher or lower than expected. So this is particularly useful for spotting problems/unusual energy use behaviour in your premises.

A final graph isn’t produced by SMEasure itself, but can easily be made by exporting your meter readings into Excel. This graph is produced when you do CUSUM analysis. CUSUM analysis is useful because it can clearly show longer term trends in your energy use – for example illustrating the impact of energy savings over time. This can be a nice way to illustrate your achievements to staff, customers and management.

The feedback that SMEasure gives you mostly relates to heating energy use as this is often the biggest user of energy in a building. However, all of these analysis tools can be used for other driving factors if you think there might be something else that strongly determines energy use in your buildings.

A good first step is to plot energy use against other factors you think might be influential (like through-put in a factory) and add a line of best fit. The closer the R value of the line is to 1, the stronger the influence of this factor. If the R-value is over 0.5 there is a reasonably strong relationship (not the same as causation!) between the factor of interest and energy use. If this is the case you will need to consider this variable when setting targets and thinking of how to reduce energy use.