Assuring Success in Energy Efficiency

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Measurement & Verification


How can you measure an energy saving?

You can't! An energy saving is the absence of energy use. It tells us how much less we have used than we would have had we not implemented an energy conservation measure (ECM).

Measurement & Verification

This might sound obvious, but there is a lot of misunderstanding and disagreement about the idea of an energy saving. For example, if I implement an ECM and my next energy bill is higher than the previous month, does that mean it has failed? Many people, not unreasonably, associate a saving with a reduction in average consumption.

In a real building, though, a variety of factors may affect the energy use, for example the weather, the number of occupants, the number of ‘widgets’ produced in a factory, or any number of other human factors. Sometimes, a change in one or more of these factors may cause energy use to increase, masking the reduction in consumption that your ECM would have given you. So unless we can take the variables into account and adjust for them, we cannot quantify the energy saving properly.

Sometimes this is unavoidable. If no-one has planned in advance how to evaluate the success of the ECM, it can be difficult to retrospectively work out how it has performed, and the best you can do is compare average consumption before and after. If energy use is reasonably consistent this may be acceptable, but it isn't very robust or structured, and leaves you open to the accusation of cheating – i.e. simply comparing two periods that give you a favourable savings figure.

Measurement & Verification

The field of ‘measurement and verification’ (M&V) has developed around the need to provide a structure to the process of objectively assessing an energy saving. Only by following a process like this can we be sure we have taken all necessary steps to take external variables into account. Done properly, M&V provides us with a ‘savings meter’, allowing energy efficiency to be valued alongside renewables as a source of clean energy in its own right. IPMVP (International Performance Measurement and Verification Protocol) provides a framework for M&V – at EEVS we use this for all our energy efficiency analysis.

Some M&V is better than none

You might assume that thorough Measurement & Verification would be very expensive, and in some cases it can be. If the evaluator has to spend large amounts of time on site taking readings and crunching through vast amounts of data, costs will increase. IPMVP advises that annual M&V costs should not be more than 10% of the annual savings, and for complex projects it may be appropriate to spend this much. But at EEVS we believe that even a basic consideration of M&V is better than none, and it is not necessary to spend anywhere near this amount.
For example, installing a new chiller: this does not have to involve an in-depth site assessment to determine the energy savings. Instead, it can often be done reliably from your half-hourly billing meter which will provide baseline data that can be analysed against temperature before the chiller is fitted. This gives you an understanding of how the building behaves, so the change that occurs when the new chiller is installed will be obvious and quantifiable. In this way, there can be no argument with the supplier that the chiller has or has not delivered savings, because the analysis method has been agreed beforehand and the methodology is objective.

We specialise in this approach – making sense of your savings using your main meter data. Our other resources pages show some of the tools we use.