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.