Czy masz niedopłatę, odkąd sprzedawca energii zmienił prognozę zużycia?

Czy is a yes/no question particle. It signals that the whole sentence is a question, similar to English do / does / is / are when we ask yes/no questions.

So:

• Masz niedopłatę. = You have an underpayment / balance due.
• Czy masz niedopłatę? = Do you have an underpayment?

In everyday spoken Polish, Czy is often optional, and people may simply rely on intonation:

• Masz niedopłatę?

That sounds natural too.

Masz is the 2nd person singular form of mieć (to have), so it means you have.

The subject ty (you) is not stated because Polish usually drops subject pronouns when the verb ending already shows who the subject is.

So:

• masz = you have
• full version: Czy ty masz niedopłatę...?

Adding ty is possible, but usually only for emphasis or contrast.

Niedopłata means an underpayment, shortfall, or amount still owed after settlement.

In bills and utilities, it often means that your estimated payments were too low, so after the actual usage is calculated, you still owe money.

Compare:

• niedopłata = you still need to pay more
• nadpłata = overpayment; you paid too much and may get money back or a credit

In this sentence, the idea is something like: Do you now owe extra money...?

Because mieć normally takes its direct object in the accusative case.

The dictionary form is:

• niedopłata (nominative)

But after masz (you have), it becomes accusative:

• masz niedopłatę

This is very common in Polish:

• Mam książkę. = I have a book.
• Masz kawę. = You have coffee.
• Masz niedopłatę. = You have an underpayment.

Since niedopłata is a feminine noun ending in -a, its accusative singular changes to -ę.

Odkąd means since or from the time when.

Here it introduces a time clause:

• odkąd sprzedawca energii zmienił prognozę zużycia
• since the energy seller changed the consumption forecast

It connects the current situation (Do you have an underpayment...?) with a point in the past (since the forecast was changed).

So the whole sentence is asking whether this underpayment has existed from that moment onward.

They are very similar, and both can often be translated as since or from when, but they are not always used in exactly the same way.

• odkąd often introduces a clause:
  Odkąd się przeprowadziłem, jestem spokojniejszy.
  = Since I moved, I’ve been calmer.

• od kiedy can also ask since when? or refer more directly to a starting point:
  Od kiedy tu pracujesz?
  = Since when have you worked here?

In your sentence, odkąd is very natural because it introduces a full event: the seller changed the forecast.

Zmienił is the past tense, masculine singular form of zmienić (to change, perfective).

It tells us a few things:

1. It happened in the past
2. The subject is grammatically masculine singular
3. The verb is perfective, so it refers to a completed change

That fits well here, because the sentence refers to a specific completed event: the seller changed the forecast.

If the subject were feminine, you would get:

• zmieniła

If plural masculine-personal:

• zmienili

Zmienił is perfective, which focuses on the completed result: the forecast was changed.

That is the natural choice here because the sentence refers to a specific event that created a new situation.

• zmienił prognozę = changed the forecast / made a change to the forecast

By contrast, zmieniał is imperfective and would usually suggest repeated action, ongoing action, or focus on the process rather than the completed result.

So:

• sprzedawca energii zmienił prognozę = natural here
• sprzedawca energii zmieniał prognozę = would sound more like was changing / used to change the forecast, which does not fit as well

Because energii is in the genitive case and works like of energy.

So:

• sprzedawca = seller
• sprzedawca energii = seller of energy, or more naturally in English, energy supplier / energy seller

This is a very common Polish pattern:

• producent samochodów = producer of cars
• sprzedawca książek = seller of books
• zużycie energii = consumption of energy

After many nouns, Polish uses the genitive to show this kind of relationship.

Energii is the genitive singular of energia.

Dictionary form:

• energia

Genitive singular:

• energii

This form is used because sprzedawca energii means seller of energy.

The same happens later in the sentence with zużycia:

• prognoza zużycia = forecast of consumption

So the sentence contains two noun + genitive combinations:

• sprzedawca energii
• prognozę zużycia

Because the main noun prognoza is the direct object of zmienił, so it appears in the accusative singular:

• prognoza → prognozę

Then zużycia is in the genitive, meaning of consumption:

• prognozę zużycia = the consumption forecast / forecast of consumption

So the structure is:

• zmienił = changed
• prognozę = forecast (accusative, because it is what was changed)
• zużycia = of consumption (genitive, dependent on prognoza)

Zużycie means consumption, usage, or amount used.

In the context of energy bills, it refers to how much electricity or gas is expected to be used.

So:

• prognoza zużycia = forecast of consumption / estimated usage
• zużycie energii = energy consumption

This is common billing vocabulary.

Not completely. Polish word order is fairly flexible, though some versions sound more neutral than others.

The original:

• Czy masz niedopłatę, odkąd sprzedawca energii zmienił prognozę zużycia?

This is natural and clear.

You could also see:

• Czy odkąd sprzedawca energii zmienił prognozę zużycia, masz niedopłatę?

This puts more focus on the time clause since the seller changed...

Because Polish uses cases and verb forms to show grammatical relationships, word order can shift for emphasis, topic, or style. Still, not every rearrangement sounds equally natural, so the original is a good standard version.

Yes, it is understandable and fairly natural, especially in a billing or customer-service context.

That said, in real-life Polish, someone might also phrase it in other ways, for example:

• Czy masz niedopłatę od czasu, gdy sprzedawca energii zmienił prognozę zużycia?
• Czy pojawiła się niedopłata, odkąd sprzedawca energii zmienił prognozę zużycia?

The original sentence sounds slightly formal or administrative, which fits the topic of energy billing.

The sentence has two parts:

1. Czy masz niedopłatę
   = Do you have an underpayment?

2. odkąd sprzedawca energii zmienił prognozę zużycia
   = since the energy seller changed the consumption forecast

So the overall pattern is:

yes/no question + time clause introduced by odkąd

More literally:

• Do you have an underpayment since the energy seller changed the consumption forecast?

In more natural English:

• Do you have an underpayment since the energy supplier changed the usage forecast?
• or better: Have you had a balance due since the energy supplier changed the consumption forecast?

The Polish structure is straightforward once you identify:

• Czy = question marker
• masz = you have
• niedopłatę = underpayment
• odkąd = since
• zmienił = changed
• prognozę zużycia = consumption forecast