| Introduction| Glossary|

M&T analysis on a 'campaign' basis

It is a basic principle of M&T, that consumption is in many instances determined by measurable driving factors according to consistent relationships which, once determined, enable accurate weekly or monthly targets to be set using expected-consumption formulae. Often the relationship between consumption and its drivers is either naturally a straight line or can be manipulated to be one; M&T analysis campaigns involve looking at these straight-line relationships, as applied to historical consumption and driver figures, to see if they make sense.

Here are three examples for buildings heated by steam. The weekly steam quantity consumed is related to the number of degree days per week (the degree day figure is an index of how cold the week was).

The first is quite a typical example. About 60,000 kg per week is used regardless of the weather, on top of which the consumption varies in proportion to the degree-day value.

Note: You might consider the illustrated target characteristic line is too low on the chart. Click here for an explanation of how such an 'aggressive' target can be shown to be achievable.

This example looks abnormal for a space-heating load since the line has a shallower slope, and higher intercept on the y axis, than might be expected. This suggests that too much heat is being delivered in mild weather (low degree-day values). Such behaviour may suggest inadequate control, excessive standing heat loss from the heating plant, or possibly (if the building has air conditioning) simultaneous heating and cooling.

This final example has the lowest fixed consumption of the three, suggesting that fuel is used exclusively for space heating and without substantial standing losses. However, the scatter of points on the chart is very broad, indicating that there are factors other than simple prevailing air temperature influencing consumption. One possible factor might be prevailing wind, and if so, the apparently high sensitivity to the wind could suggest that the building is insufficiently draughtproof.