Die Anlagenleistung bestimmt den Stromverbrauch.

Because the two nouns have different genders and different roles in the sentence.

• Anlagenleistung is a feminine noun because the last part, Leistung, is feminine. So in the nominative singular, it takes die.
• Stromverbrauch is a masculine noun because Verbrauch is masculine. Here it is the direct object, so it takes the masculine accusative article den.

So:

• die Anlagenleistung = nominative subject
• den Stromverbrauch = accusative object

That is one of the main clues that tells you who is doing what in the sentence.

German often shows this through case marking, especially in the articles.

In Die Anlagenleistung bestimmt den Stromverbrauch:

• die Anlagenleistung is the subject because it is in the nominative
• den Stromverbrauch is the direct object because den marks masculine accusative

So the sentence means that the system/output capacity determines the electricity consumption, not the other way around.

In English, word order usually tells you this. In German, word order matters too, but case is often even more important.

Because the verb is conjugated to match the subject.

The infinitive is bestimmen = to determine.

The subject here is die Anlagenleistung, which is third person singular (it), so the verb becomes:

• ich bestimme
• du bestimmst
• er/sie/es bestimmt

So:

• Die Anlagenleistung bestimmt ...

means The system/output capacity determines ...

Yes. German very often forms compound nouns by combining smaller nouns into one longer word.

Here:

• Anlage = installation, system, plant, facility
• Leistung = performance, output, power, capacity

Together, Anlagenleistung is a technical compound noun. Depending on context, it can mean something like:

• system capacity
• plant output
• installed power
• performance of the installation

German writes these as one word, not as separate words.

Not necessarily. This is a very common learner question.

The Anlagen- part can look like the plural of Anlage, but in compounds German often uses a linking element (called a Fugenlaut), and -n- is a very common one.

So in a compound, Anlagen- does not automatically mean plural.

You usually understand it from context:

• sometimes it really reflects a plural idea
• sometimes it is just the normal form used inside a compound

For learners, the safest approach is: treat Anlagenleistung as a fixed compound noun and learn its meaning from context.

In German compound nouns, the last element decides the gender.

Here the last part is Leistung, and Leistung is feminine:

• die Leistung

So the whole compound is also feminine:

• die Anlagenleistung

This rule is extremely useful in German:

• das Haus
  • die Tür → die Haustür
• der Strom
  • der Verbrauch → der Stromverbrauch
• die Anlage
  • die Leistung → die Anlagenleistung

The final noun controls:

• gender
• plural pattern
• basic grammatical behavior

Here bestimmen means to determine, to dictate, or to have a deciding influence on.

So the sentence does not mean just describe or name. It means that one thing affects or controls the other in an important way.

Depending on context, bestimmen can also mean:

• to determine
• to specify
• to define
• to decide

But in this sentence, the meaning is clearly something like:

• The system/output capacity determines the electricity consumption

Stromverbrauch is another compound noun:

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

So Stromverbrauch means:

• electricity consumption
• power consumption
  (depending on context, though technically electricity consumption is often the safer translation)

It is a masculine noun:

• der Stromverbrauch

And in your sentence it becomes accusative:

• den Stromverbrauch

Yes, German word order is more flexible than English, because the case endings help show the roles.

For example, you could also say:

• Den Stromverbrauch bestimmt die Anlagenleistung.

This still means the same thing, because:

• den Stromverbrauch is still accusative
• die Anlagenleistung is still nominative

But the emphasis changes. Putting Den Stromverbrauch first gives it more focus.

The verb still stays in the second position in a normal main clause:

• Den Stromverbrauch | bestimmt | die Anlagenleistung

Because in German, all nouns are capitalized.

So in this sentence:

• Anlagenleistung is capitalized because it is a noun
• Stromverbrauch is capitalized because it is a noun

This is standard German spelling and applies everywhere, not just at the beginning of a sentence.

It is singular.

Even though Anlagenleistung contains Anlagen-, the full noun die Anlagenleistung is treated here as one singular noun.

You can tell from the verb:

• bestimmt = singular
• if the subject were plural, you would expect bestimmen

So:

• Die Anlagenleistung bestimmt ... = singular subject

If it were plural, it might look like:

• Die Anlagenleistungen bestimmen ...

which would mean The system capacities determine ...