The expected-consumption formula

A key aspect of monitoring and targeting is the calculation of expected consumption for comparison with what was actually used. One good way of doing this (but not the only way) is to relate consumption to some driving factor using a straight-line relationship as illustrated here. The typical driving factors for energy consumption (in simple cases) are things like: Production throughput Weather (measured as heating or cooling degree days) Mileage, or tonne miles etc. These are all things which can be measured, on a weekly or monthly basis, and expressed as a single number. Real-world complications: not every process conforms to the ideal of a straight-line relationship between consumption and a single measurable driving factor. Follow the links to learn about: curved lines, multiple driving factors, varying product grades, and complex scenarios. Whatever the situation, we will have a mathematical formula into which we put the measured driving-factor values in order to obtain an estimate of expected consumption. This is called the expected-consumption formula (ECF).

ECFs can be used for different purposes by adjusting the constants used in the formula. Where a straight-line model is used, these constants are the slope of the line and the intercept on the vertical (energy) axis. By setting these as low as possible, the performance characteristic represents best achievable performance and would be used for routine exception reporting. Click here to learn how to set the characteristic line at the lowest feasible position.

Another important characteristic is the historical baseline. This represents behaviour as it was at the start of your energy-saving programme and it uses the same ECF as the target characteristic, but with any constants set to represent performance as it was at the time.

In general each consumption stream has just one ECF but this may be "set" to compute expected consumption for whichever purpose is needed (operational target, historical baseline, budget projection, etc) by using different values for the constants in the ECF.