يخفض مدقق الطاقة استهلاك الطاقة بالعداد الذكي.

Because Arabic very often uses verb–subject–object order, especially in straightforward statements.

So:

• يخفض مدقق الطاقة استهلاك الطاقة... = literally reduces the energy auditor the energy consumption...

This is normal Arabic word order.
You could also say:

• مدقق الطاقة يخفض استهلاك الطاقة...

That version is also correct, but it puts more focus on the energy auditor as the topic.

يخفض is a present/imperfect tense verb, 3rd person masculine singular.

It means:

• he reduces / lowers
• or sometimes it reduces / lowers, depending on the subject

Here the subject is مدقق الطاقة, which is masculine singular, so يخفض matches it.

The يـ at the beginning is the usual prefix for he / it in this tense.

Because مدقق الطاقة is an iḍāfa construction, often called a construct phrase.

In an iḍāfa:

• the first noun normally does not take ال
• the second noun shows whether the whole phrase is definite

So:

• مدقق الطاقة = auditor of the energy → naturally the energy auditor

Since الطاقة is definite because it has ال, the whole phrase becomes definite.

This is why Arabic says:

• مدقق الطاقة

not

• المدقق الطاقة

It is a noun phrase made of:

• مدقق = auditor / checker / inspector
• الطاقة = energy

Together, they form an iḍāfa:

• مدقق الطاقة = energy auditor

Grammatically, this whole phrase is the subject of the verb يخفض.

استهلاك الطاقة is the direct object of the verb يخفض.

It means:

• energy consumption

Again, this is another iḍāfa phrase:

• استهلاك = consumption
• الطاقة = energy

So the structure is:

• يخفض = reduces
• مدقق الطاقة = the energy auditor
• استهلاك الطاقة = energy consumption

In other words, energy consumption is the thing being reduced.

Because the sentence contains two different iḍāfa phrases:

• مدقق الطاقة = energy auditor
• استهلاك الطاقة = energy consumption

Even though English might sometimes avoid repetition, Arabic often repeats the noun naturally when it belongs to two different noun phrases.

So the two instances of الطاقة are not redundant; each one belongs to a different structure.

Here بـ means something like:

• with
• by means of
• using

So:

• بالعداد الذكي = with the smart meter / using the smart meter

Also, بالعداد is just:

• بِ + العداد

written together, as is normal in Arabic.

Because Arabic adjectives normally come after the noun they describe.

So:

• العداد الذكي = the smart meter

not the English order smart meter.

Also, adjectives in Arabic must agree with the noun they describe in:

• definiteness
• gender
• number
• case

Since العداد is:

• masculine
• singular
• definite

the adjective must match it:

• الذكي

If the noun has ال, the adjective usually has ال too.

A fully vocalized version would be:

يَخْفِضُ مُدَقِّقُ الطَّاقَةِ اسْتِهْلَاكَ الطَّاقَةِ بِالْعَدَّادِ الذَّكِيِّ.

This helps show the grammar:

• يَخْفِضُ = verb
• مُدَقِّقُ = subject, nominative
• الطَّاقَةِ = genitive because it is the second part of iḍāfa
• اسْتِهْلَاكَ = direct object, accusative
• الطَّاقَةِ = genitive in iḍāfa
• بِالْعَدَّادِ = genitive after بِ
• الذَّكِيِّ = adjective agreeing with العداد

There are a few clues:

• After a verb, Arabic commonly places the subject next.
• مدقق الطاقة is a person/job title, so it makes sense as the doer.
• استهلاك الطاقة is an abstract thing, so it makes sense as the thing being reduced.

With full case endings, the roles are even clearer:

• مُدَقِّقُ has nominative -u → subject
• اسْتِهْلَاكَ has accusative -a → direct object

In everyday unvowelled Arabic, readers usually rely on syntax and meaning to understand this.

In this sentence, the most natural reading is that it modifies the action:

• the energy auditor reduces energy consumption using the smart meter

So it most naturally goes with يخفض.

In theory, Arabic prepositional phrases can sometimes be ambiguous, but here context strongly favors the instrumental meaning with / by means of the smart meter, rather than describing one of the nouns.