Višak električne energije je velik.

Because višak usually takes the genitive: it means a surplus/excess of something.

So:

• višak = surplus / excess
• energija = energy
• energije = of energy (genitive singular)

The adjective električne agrees with energije, so it is also genitive singular feminine:

• električna energija = electrical energy
• električne energije = of electrical energy

So the structure is:

• višak + genitive
• višak električne energije = a surplus of electrical energy

Because the grammatical subject is višak, and višak is a singular masculine noun.

Even though the whole phrase contains more words, the core noun is still višak:

• Višak električne energije je velik.

So Croatian treats this as:

• The surplus is large.

Not:

• The electrical energy is large.

That is why the verb is je (is), not a plural form.

Because velik agrees with višak, which is masculine singular.

Agreement in Croatian depends on the noun being described or linked to the predicate:

• masculine singular: velik
• feminine singular: velika
• neuter singular: veliko
• masculine plural: veliki, etc.

Since višak is masculine singular, the correct form is:

• Višak ... je velik.

This is a very common learner question.

After je in a predicate, Croatian normally uses the short/indefinite adjective form:

• On je velik.
• Problem je ozbiljan.
• Višak električne energije je velik.

The form veliki is the long/definite form, more typical when the adjective stands directly before a noun:

• velik problem = a big problem
• veliki problem = often the big/significant problem or a more definite/stylistically marked form

So in this sentence, je velik is the normal predicative pattern.

Here, višak is in the nominative singular, because it is the subject of the sentence.

You can see the basic structure as:

• Višak = subject
• je = verb
• velik = predicate adjective

Then električne energije is a dependent genitive phrase attached to višak.

So:

• višak — nominative singular
• električne energije — genitive singular

Here it is genitive singular.

That can be confusing, because some Croatian noun forms can look like plurals to English speakers. But in this sentence:

• dictionary form: energija
• genitive singular: energije

So električne energije means of electrical energy, not electrical energies.

Yes, Croatian word order is fairly flexible, but the given order is the most neutral and straightforward:

• Višak električne energije je velik.

Other orders are possible for emphasis, for example:

• Velik je višak električne energije.

This can sound more emphatic, like The surplus of electrical energy is large with extra focus on large.

For learners, the original version is the safest neutral pattern:

• subject + je + adjective

Not in normal standard Croatian prose or speech.

Croatian does not usually omit the present tense of biti (to be) in ordinary sentences like this:

• Višak električne energije je velik. ✅

Without je, it would sound incomplete in standard language. You might see omission in headlines, notes, or very compressed styles, but not as the normal sentence pattern.

Because Croatian has no articles like English a/an/the.

So:

• višak can mean a surplus or the surplus
• the exact sense depends on context

In this sentence, English might translate it as either:

• The surplus of electrical energy is large
• A surplus of electrical energy is large

depending on the broader situation. Croatian does not mark that distinction with an article.

The main ones here are:

• š in Višak: like sh in shoe
• č in električne: like ch in chocolate, but typically a bit firmer/crisper in Croatian

A rough pronunciation guide:

• Višak ≈ VEE-shak
• električne ≈ eh-lek-TREECH-neh
• energije ≈ eh-nehr-GHEE-yeh
• je ≈ yeh
• velik ≈ VEH-leek

Stress in Croatian is not usually marked in normal writing, so beginners often just learn the pronunciation by listening.

All of those are related, but višak is a noun, so in this sentence it is best understood as:

• surplus
• excess

So:

• Višak električne energije je velik.
• The surplus/excess of electrical energy is large.

If you wanted to say there is too much electrical energy, Croatian would usually use a different structure, not necessarily this noun phrase.

So the key point is:

• višak = a thing/state of being extra, a surplus
• not directly the adverbial idea too much

Not exactly.

• električna energija = electrical energy
• struja = electric current / electricity in many everyday contexts

In everyday Croatian, people often say struja when they mean electrical power or electricity in general. But električna energija is more technical or formal.

So this sentence sounds somewhat formal/technical, which fits topics like energy systems, production, or engineering.

No, that would not be correct here.

After je, you want the normal predicate adjective form:

• je velik ✅
• je veliki ❌

So the sentence should stay:

• Višak električne energije je velik.

That is one of the most useful patterns to remember:

• X je velik
• X je važan
• X je dobar

not:

• X je veliki
• X je važni
• X je dobri