La classe energetica è bassa, cioè l'edificio consuma molto.

Because classe is a feminine noun in Italian, so it takes the feminine article la.

• la classe = the class / rating
• energetica must also be feminine singular because it agrees with classe

So:

• la classe energetica = the energy rating / energy class

In Italian, adjectives usually agree with the noun in gender and number.

Energetica means energy-related or energetic in the sense of energy use, not in the sense of a lively person.

In this sentence, classe energetica is a fixed expression often used for the official energy efficiency rating of a building, appliance, or home.

So energetica is describing the type of classe.

È with an accent is the 3rd person singular of essere:

• è = is

The accent is important because:

• è = is
• e = and

So in this sentence:

• La classe energetica è bassa = The energy rating is low

Without the accent, it would be a different word.

Because bassa agrees with classe, which is feminine singular.

Agreement works like this:

• masculine singular: basso
• feminine singular: bassa
• masculine plural: bassi
• feminine plural: basse

Since the noun is la classe, the adjective must be bassa.

Cioè means something like:

• that is
• in other words
• that is to say
• sometimes namely

Here it introduces a clarification or explanation:

• La classe energetica è bassa, cioè l'edificio consuma molto.

So the second part explains what the first part means in practical terms.

It is very common in spoken and written Italian when reformulating or explaining something.

Because edificio starts with a vowel, and il becomes l' before a vowel.

So:

• il libro
• l'edificio

This is called elision.

Also note that edificio is masculine, so the full article would normally be il, not lo or la.

Consuma is the 3rd person singular present tense of consumare:

• consumare = to consume, to use up

Since the subject is l'edificio (the building), Italian uses the he/she/it form:

• l'edificio consuma = the building consumes / uses

Italian often uses the same verb form for he, she, and it, so context tells you which one it is.

Because Italian usually drops subject pronouns when they are not needed.

English says:

• it consumes a lot

Italian normally just says:

• consuma molto

The verb ending already shows the person/number, and here the subject l'edificio is stated explicitly, so no extra pronoun is needed.

Here molto means a lot or a great deal, and it is being used as an adverb modifying the verb consuma.

• consuma molto = consumes a lot

When molto is an adverb, it does not change form.

Compare:

• molto grande = very big
• consuma molto = consumes a lot

But when molto is an adjective, it agrees with the noun:

• molta energia = a lot of energy
• molti edifici = many buildings

So in this sentence, molto stays unchanged because it modifies the verb.

Linguistically, bassa just means low, but in this context it refers to energy efficiency rating, so a low rating is usually bad.

That is why the sentence explains it with:

• l'edificio consuma molto = the building uses a lot of energy

So the Italian sentence is helping you understand that bassa here implies poor efficiency.

Not with exactly the same meaning.

• cioè introduces a restatement or explanation: that is / in other words
• perché means because

So:

• La classe energetica è bassa, cioè l'edificio consuma molto.
  = The energy rating is low, that is, the building consumes a lot.

This explains the first statement.

But:

• La classe energetica è bassa perché l'edificio consuma molto.
  = The energy rating is low because the building consumes a lot.

This gives the reason for the low rating.

Both are possible, but they do slightly different jobs.

The most neutral Italian word order is usually:

• subject + verb + other elements

So:

• l'edificio consuma molto

That is the most straightforward order.

Italian can change word order for emphasis, but consuma molto l'edificio would sound marked or unusual in normal context. A learner should usually stick with the standard order unless there is a special reason to move words around.

It is pronounced approximately like cho-EH, with the stress on the last part.

A rough guide:

• ci before o sounds like ch
• oè is pronounced in two syllables

So cioè is about cho-EH.

Also, the accent on è shows the stress and helps distinguish the word in writing.