Dokud nesnížíme spotřebu energie, úspora nebude velká.

This is a very common point of confusion for English speakers.

In Czech, dokud often appears with a negative perfective verb to express the idea of English until.

So:

• Dokud nesnížíme spotřebu energie, ...
  means Until we reduce energy consumption, ...

Even though nesnížíme is formally negative, the whole structure does not mean until we do not reduce. It means that the action in the main clause continues up to the point when the reduction happens.

This is a normal Czech pattern:

• Dokud nepřijde, nezačneme. = We won’t start until he comes.
• Dokud to neuděláš, nepomůžu ti. = Until you do it, I won’t help you.

So here, ne- is part of the standard grammar after dokud in this kind of sentence.

Because snížit is a perfective verb.

In Czech, perfective verbs do not normally have a true present tense meaning. Their non-past forms usually refer to the future.

So:

• snížíme literally looks like a present form
• but with a perfective verb, it means we will reduce

Compare:

• snižujeme = we are reducing / we reduce
  imperfective
• snížíme = we will reduce
  perfective

That is why nesnížíme here means we do not reduce yet / we will not have reduced, depending on context, and in this sentence it works as until we reduce.

The key difference is aspect:

• snížit = perfective
  focuses on a completed result: to reduce
• snižovat = imperfective
  focuses on process, repetition, or ongoing action: to be reducing / to reduce regularly

In this sentence, the speaker is talking about reaching a result:

• until we reduce energy consumption

That is why snížit is the natural choice.

If you used the imperfective, the meaning would shift more toward process or habitual action, and it would not fit as neatly here.

Because spotřebu is the accusative singular form, and it is the direct object of the verb snížit.

Dictionary form:

• spotřeba = consumption

Cases:

• spotřeba = nominative singular
• spotřebu = accusative singular

Since we are saying reduce what? → consumption, Czech uses the accusative:

• snížit spotřebu

So:

• nesnížíme spotřebu energie = we do not reduce energy consumption

Because energie here depends on spotřeba and means consumption of energy.

After a noun like spotřeba (consumption), Czech commonly uses the genitive:

• spotřeba čeho? = consumption of what?
• energie

For the noun energie, the genitive singular is also energie, which happens to look the same as the nominative singular.

So:

• spotřeba energie = energy consumption

By contrast:

• energii is usually accusative singular or dative singular

That would not fit here.

Because úspora is the subject of the main clause.

Main clause:

• úspora nebude velká

Ask:

• What will not be large?
• úspora = the saving / the savings

So úspora is in the nominative, the normal case for the subject.

Because velká agrees with úspora.

• úspora is feminine singular nominative
• so the adjective must also be feminine singular nominative

That gives:

• velká úspora = a large saving
• úspora nebude velká = the saving will not be large

This is standard adjective agreement in Czech.

Because the main clause talks about the future:

• úspora nebude velká = the saving will not be large

The verb být (to be) forms the future like this:

• budu, budeš, bude, budeme, budete, budou

With negation:

• nebudu, nebudeš, nebude, nebudeme, nebudete, nebudou

So:

• nebude = will not be

It agrees with úspora, which is third person singular.

In this sentence, either can work depending on context.

• úspora literally means saving
• in natural English, savings may sometimes sound better

So the sentence could be understood as:

• Until we reduce energy consumption, the savings won’t be large.
• Until we reduce energy consumption, the saving won’t be significant.

If the context is economics, environment, or efficiency, English often prefers savings.

Because the sentence begins with a subordinate clause:

• Dokud nesnížíme spotřebu energie, ...

Then comes the main clause:

• úspora nebude velká.

In Czech, subordinate clauses are separated by commas. Since the dokud clause comes first, a comma is needed before the main clause.

This is very standard Czech punctuation.

Yes. Czech word order is flexible, although some versions sound more natural than others.

The original sentence:

• Dokud nesnížíme spotřebu energie, úspora nebude velká.

You could also say:

• Úspora nebude velká, dokud nesnížíme spotřebu energie.

That means essentially the same thing: The savings won’t be large until we reduce energy consumption.

The version with dokud first often sounds a bit more structured or emphatic, because it sets the condition first.

A rough English-friendly guide is:

• ne-SNEE-zhee-meh

More carefully:

• ne = short neh
• sní = like snee
• ží = like zhee
• me = meh

A few sound notes:

• ž sounds like the s in measure
• í is a long ee
• Czech stress is usually on the first syllable, so: NE-sní-ží-me

In this sentence, that would not sound right.

With dokud, Czech normally uses the negative form in this until meaning:

• Dokud nesnížíme spotřebu energie, ...

If you remove the ne-, the sentence becomes unnatural or changes the structure in a way that native speakers would not normally use here.

So for learners, the safest rule is:

• with dokud meaning until, expect negative perfective very often

It is basically:

• Dokud + negative perfective verb clause,
  main clause in the future

So here:

1. Dokud nesnížíme spotřebu energie
   = Until we reduce energy consumption
2. úspora nebude velká
   = the savings will not be large

This is a very useful Czech pattern for expressing:

• until X happens, Y will not happen / will remain true

You can use it in many everyday sentences.