this is a weak and somewhat unreliable method, based on the assumption that annual seasonal variations are consistent. While that's true for a small number of cases, the big problem is that consumption in the period you're comparing with might itself have been incorrect
this method assumes that you use energy or other commodity in direct proportion to the measured product output. Dividing energy used by product output gives a figure for kWh per unit produced, which can then be compared with a target ratio. It's a weak approach because actually there are very few processes which exhibit a constant SER; most SERs are variable because there is always an element of fixed, non-throughput-related, consumption.
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the main method propounded in this Guide,
this explicitly allows for the fixed element of consumption which
SER method ignores. The target is in two parts: a fixed ration for the
time-interval spanned, and a variable ration in direct proportion to
production (or other driving factor), giving a straight-line relationship
as illustrated opposite.
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this method must be used for complex scenarios, such as irregular batch production, where numerous factors determine the energy requirement. Strictly speaking this is a particular case of activity-based targeting.