Etterisoleringen reduserer strømforbruket.

Etterisoleringen means the additional insulation, the retrofit insulation, or the act/process of insulating something afterwards.

It is built from:

• etter- = after, afterwards
• isolering = insulation / insulating

So etterisolering is not just insulation in general; it specifically refers to adding insulation to something that already exists, such as an older house.

Because Norwegian normally writes compound nouns as one word.

So:

• etter
  • isolering → etterisolering
• strøm
  • forbruk → strømforbruk

This is very common in Norwegian. English often writes similar ideas as two words, but Norwegian usually joins them.

A useful rule is that the last part is the main noun. In etterisolering, the core word is isolering.

The ending -en is the definite article attached to the noun. In English, you use a separate word: the. In Norwegian, it is often added to the end of the noun.

So:

• etterisolering = additional insulation / retrofit insulation
• etterisoleringen = the additional insulation / the retrofit insulation

Here, isolering is a common-gender noun in Bokmål, so the definite singular ending is -en.

Because Norwegian usually expresses definiteness with an ending, not with a separate word.

So instead of:

• English: the insulation
• Norwegian: isoleringen

And instead of:

• English: the electricity consumption
• Norwegian: strømforbruket

A separate word like den/det is often used when there is an adjective:

• etterisoleringen = the retrofit insulation
• den nye etterisoleringen = the new retrofit insulation

This is a very common pattern in Norwegian.

Reduserer is the present tense of å redusere, which means to reduce.

So:

• å redusere = to reduce
• reduserer = reduce / reduces

Unlike English, Norwegian verbs do not change depending on the subject:

• jeg reduserer
• du reduserer
• han reduserer
• etterisoleringen reduserer

So reduserer works for I, you, he/she/it, and noun subjects.

Strømforbruket means the electricity consumption or the power consumption.

It is another compound noun:

• strøm = electricity / electric power
• forbruk = consumption, use

Together:

• strømforbruk = electricity consumption
• strømforbruket = the electricity consumption

Again, Norwegian usually joins compound nouns into one word.

Because the main noun here is forbruk, and forbruk is a neuter noun.

So:

• et forbruk = a consumption
• forbruket = the consumption

When it becomes part of a compound, the gender of the last element still controls the ending:

• strømforbruk = electricity consumption
• strømforbruket = the electricity consumption

So -et tells you it is definite singular neuter.

This sentence has the normal main-clause word order:

• Etterisoleringen = subject
• reduserer = verb
• strømforbruket = object

So it follows the basic pattern:

Subject + Verb + Object

However, Norwegian main clauses also follow the V2 rule, which means the finite verb usually comes in the second position. If you move something else to the front, the verb still stays second:

• Etterisoleringen reduserer strømforbruket.
• I gamle hus reduserer etterisoleringen strømforbruket.

That second example shows the same verb placement rule.

Yes, you could, but the meaning changes slightly.

• Etterisoleringen reduserer strømforbruket = the retrofit insulation reduces electricity consumption

  • This usually refers to a specific insulation measure already known from the context.

• Etterisolering reduserer strømforbruket = retrofit insulation reduces electricity consumption

  • This sounds more like a general statement.

So the definite form -en makes it more specific.

They are related, but not identical.

• isolasjon usually means insulation in a general sense, often the material or the concept
• etterisolering means adding insulation later, especially to an existing building

So if you are talking about a renovation step in an older house, etterisolering is more precise.

For example:

• Huset har god isolasjon = The house has good insulation
• Huset trenger etterisolering = The house needs additional insulation / retrofit insulation

So in your sentence, etterisoleringen refers to the improvement work, not just insulation as a general material.