Use of singular or plural in “the sum of the power consumption(s)”

Question

Should consumption/consumptions be in singular or in plural here?

1. The total power consumption of a circuit is the sum of the power consumption of the logic cells making up the circuit.

2. The total power consumption of a circuit is the sum of the power consumptions of the logic cells making up the circuit.

Can you have more than one power consumption? Or is consumption uncountable like power is here? How can one in general know what kind of a noun one is dealing with? Are there rules governing this that native speakers all know?

Is this particular context some sort of special case compared with normal usage because of its mathematical nature?

Answer 1

Consumption is a mass noun which does not have a plural form. So, the answer is to use "consumption".

https://en.oxforddictionaries.com/definition/consumption indicates that consumption is a "[mass noun]".

https://en.oxforddictionaries.com/grammar/countable-nouns explains what a mass noun is. "Nouns can be either countable or uncountable. Countable nouns (or count nouns) are those that refer to something that can be counted. They have both singular and plural forms (e.g. cat/cats; woman/women; country/countries). In the singular, they can be preceded by a or an. Most nouns come into this category. A smaller number of nouns do not typically refer to things that can be counted and so they do not regularly have a plural form: these are known as uncountable nouns (or mass nouns). Examples include: rain, flour, earth, wine, or wood. Uncountable nouns can't be preceded by a or an. Many abstract nouns are typically uncountable, e.g. happiness, truth, darkness, humour."