Le fournisseur d’énergie facture le montant dû.

Here, facture is a verb: the third-person singular present form of facturer.

So the structure is:

• Le fournisseur d’énergie = the subject
• facture = bills / charges / invoices
• le montant dû = the direct object

This can confuse learners because une facture is also a noun meaning bill or invoice.

Compare:

• Le fournisseur facture le montant dû. = the supplier bills the amount due
• La facture est envoyée. = the bill is sent

Same spelling, different job in the sentence.

Because de becomes d’ before a vowel sound.

So:

• de + énergie → d’énergie

This is called elision. French does it to avoid a clumsy vowel sequence.

You see the same thing in:

• d’accord
• d’habitude
• l’énergie
• j’aime

The apostrophe does not change the meaning; it is just the normal written form before a vowel or mute h.

In phrases like fournisseur d’énergie, French often uses de with no article to show a general relationship, category, or function.

So fournisseur d’énergie means:

• supplier of energy
• energy supplier

This is similar to:

• compagnie d’assurance = insurance company
• centre de formation = training center
• fournisseur d’accès = access provider

If you said de l’énergie, it would sound less like a fixed category label and more like you were talking about some energy or the energy in a more literal sense.

Facturer means to bill, to charge, or to invoice.

In business or administrative French, it often means that a company officially charges an amount and puts it on an invoice or statement.

A useful pattern is:

• facturer quelque chose à quelqu’un

Examples:

• Le fournisseur facture le service au client.
• On vous facturera les frais plus tard.

In your sentence, the person being billed is simply not mentioned.

Because le montant dû is the thing being billed, so it is the direct object of facturer.

With facturer, the usual pattern is:

• facturer quelque chose à quelqu’un

So:

• quelque chose = direct object
• à quelqu’un = indirect object

In your sentence:

• le montant dû = what is being billed

If you wanted to add the person, you could say:

• Le fournisseur d’énergie facture le montant dû au client.

So the missing à is not a mistake; it would only appear before the person receiving the charge.

Here, dû means due or owed.

It comes from the verb devoir, whose past participle is dû.

In this sentence, it is being used like an adjective to describe montant:

• le montant dû = the amount owed / the amount due

You will often see dû in formal, financial, or administrative French:

• la somme due = the sum due
• les montants dus = the amounts owed

So although it comes from a verb, here it functions as a descriptive word attached to the noun.

The accent in dû is part of the standard spelling.

It is especially useful because it helps distinguish dû from du:

• dû = due / owed, or past participle of devoir
• du = contraction of de + le

Compare:

• le montant dû = the amount owed
• du montant = of the amount

So the accent is important because it prevents confusion.

Because in French, this kind of adjective or participle usually comes after the noun.

So:

• montant dû = amount due
• somme due = sum owed

This is very normal in French, even though English often puts the equivalent word before the noun:

• due amount is possible in English, but amount due is also common
• in French, montant dû is the natural choice

More generally, many descriptive words in French come after the noun, especially when they are:

• participles
• longer or more formal descriptors
• part of a fixed expression

French uses the definite article very often, sometimes more often than English does.

Here:

• Le fournisseur d’énergie can mean a specific energy supplier known from context, or a generic institutional subject depending on the situation
• le montant dû refers to the specific amount that is owed

English sometimes drops articles where French keeps them, but French usually prefers an article with nouns like these.

Compare:

• Le client paie la facture.
• Le fournisseur envoie le document.

Using le here is completely normal French.

Yes, facture is in the present tense.

In French, the present can express several things depending on context:

• a general fact
  
  • Le fournisseur d’énergie facture le montant dû.
• a habitual action
  
  • the supplier regularly bills the amount due
• an action happening now
  
  • the supplier is billing the amount due

French often uses the simple present where English might choose either:

• bills
• is billing

If you really want to stress right now, French can use:

• est en train de facturer

But the simple present is very common and natural.

A rough pronunciation guide is:

luh foo-rnee-sur day-nayr-zhee fak-tur luh mon-tahn dyu

A few useful pronunciation points:

• fournisseur ends with the French r, not an English r
• d’énergie flows together because of the elision
• montant has a nasal vowel, so the n is not pronounced like a full English n
• dû has the French u sound, which is different from English oo

A more IPA-style version is:

lə fuʁ.ni.sœʁ de.nɛʁ.ʒi fak.tyʁ lə mɔ̃.tɑ̃ dy

If you are reading it aloud, try to make it smooth rather than choppy.