Sobald der Filtereinsatz sauber ist, sinkt der Stromverbrauch.

Because sobald introduces a subordinate clause. In German, the conjugated verb normally goes to the end of a subordinate clause.

So:

• Sobald = subordinating conjunction
• der Filtereinsatz = subject
• sauber = predicate adjective
• ist = conjugated verb, placed at the end

That is why you get:

Sobald der Filtereinsatz sauber ist

and not Sobald der Filtereinsatz ist sauber.

The comma separates the subordinate clause from the main clause.

• Subordinate clause: Sobald der Filtereinsatz sauber ist
• Main clause: sinkt der Stromverbrauch

In German, subordinate clauses are normally set off by a comma, especially when introduced by words like:

• weil
• dass
• wenn
• sobald
• obwohl

So the comma here is required.

Because the subordinate clause comes first, it takes up the first position in the sentence. In German main clauses, the conjugated verb must be in second position.

So the structure is:

1. Sobald der Filtereinsatz sauber ist = position 1
2. sinkt = position 2
3. der Stromverbrauch = rest of the clause

That is why the word order is:

Sobald der Filtereinsatz sauber ist, sinkt der Stromverbrauch.

If you start with the main clause instead, then you get:

Der Stromverbrauch sinkt, sobald der Filtereinsatz sauber ist.

Both are correct.

Sobald usually means as soon as or once. It emphasizes that one thing happens immediately after another condition is met.

So here it suggests:

• once the filter insert is clean,
• the power consumption goes down

Wenn can also mean when or if, depending on context, but it is often more general and less immediate.

Compare:

• Sobald der Filtereinsatz sauber ist, sinkt der Stromverbrauch.
  = As soon as the filter insert is clean, power consumption drops.

• Wenn der Filtereinsatz sauber ist, sinkt der Stromverbrauch.
  = When/if the filter insert is clean, power consumption drops.

In many contexts both are possible, but sobald feels more specifically tied to the moment the condition is fulfilled.

Because sauber is being used as a predicate adjective, not an adjective directly before a noun.

In German:

• ein sauberer Filtereinsatz = a clean filter insert
  Here the adjective comes before the noun, so it takes an ending.

• Der Filtereinsatz ist sauber. = The filter insert is clean.
  Here the adjective comes after sein, so it does not take an ending.

That is exactly what happens in your sentence.

Both are in the nominative case because both are subjects of their own clauses.

• der Filtereinsatz is the subject of ist
• der Stromverbrauch is the subject of sinkt

So:

• der Filtereinsatz = nominative singular, masculine
• der Stromverbrauch = nominative singular, masculine

Even though der appears twice, the two nouns belong to different clauses and each is the subject in that clause.

Because both Filtereinsatz and Stromverbrauch are masculine singular nouns in the nominative case.

German articles depend on:

• gender
• number
• case

Here both nouns are:

• masculine
• singular
• nominative

So both take der.

This does not mean they are the same word type in every context. If the case changed, the article could change too:

• den Filtereinsatz = accusative
• des Stromverbrauchs = genitive

Yes. German very often forms compound nouns, and Filtereinsatz is one of them.

It is made up of:

• Filter = filter
• Einsatz = insert, element, component, use, deployment depending on context

Together, Filtereinsatz means something like filter insert, filter element, or filter cartridge, depending on the technical context.

A useful rule for German compounds:

• the last part is the main noun
• the earlier part modifies it

So Filtereinsatz is a kind of Einsatz related to a Filter.

Literally, it is a compound of:

• Strom = electricity / electric current / power
• Verbrauch = consumption, usage

So Stromverbrauch means electricity consumption or power consumption.

Like many German compounds, it is written as one word.

Yes. German often uses the present tense for:

• general truths
• regular results
• future events that are clear from context

So this sentence can mean a general fact:

• whenever the filter insert is clean, power consumption drops

It can also imply a future result:

• once the filter insert becomes clean, power consumption will drop

German does not need a separate future form here. The present tense sounds natural.

Yes, absolutely. That version is also correct.

Compare:

• Sobald der Filtereinsatz sauber ist, sinkt der Stromverbrauch.
• Der Stromverbrauch sinkt, sobald der Filtereinsatz sauber ist.

The meaning is basically the same. The difference is mainly focus:

• starting with Sobald... emphasizes the condition/time relationship first
• starting with Der Stromverbrauch... emphasizes the result first

The word order changes because in a main clause the finite verb still has to stay in second position.