Matumizi yaliyokadiriwa ya umeme ni makubwa.

Because Swahili noun classes do not match English singular/plural patterns exactly.

Matumizi is normally treated as a class 6 noun, so other words in the sentence must agree with that class:

• yaliyokadiriwa
• ya
• makubwa

In English, usage/consumption may feel singular, but in Swahili the grammar follows the noun class of matumizi, not English logic.

Matumizi means use, usage, consumption, or expenditure, depending on context.

In this sentence, because it is followed by ya umeme, it means something like:

• electricity usage
• electricity consumption

So matumizi ya umeme is use/consumption of electricity.

Yaliyokadiriwa means estimated or more literally that have been estimated.

It describes matumizi, so:

• matumizi yaliyokadiriwa = estimated usage/consumption

This is a very common Swahili pattern: a verb form can function like an adjective.

It is a relative verb form agreeing with matumizi.

A simple way to understand it is:

• ya- = agreement with class 6 noun matumizi
• -liyo- = relative element, roughly which/that
• kadiriwa = be estimated (passive form)

So the whole word means something like which has/have been estimated.

In natural English, you would usually just say estimated.

Because in this kind of of phrase, the connector agrees with the first noun, not the second one.

Here the first noun is matumizi, and since matumizi is class 6, the connector is ya:

• matumizi ya umeme = use/consumption of electricity

So ya is agreeing with matumizi, not with umeme.

Ni is the copula, the word that works like is/are.

So:

• Matumizi yaliyokadiriwa ya umeme ni makubwa means
• The estimated electricity consumption is high/large

Without ni, the sentence would be missing the basic link between the subject and what is being said about it.

Because adjectives in Swahili must agree with the noun class of the noun they describe.

Since matumizi is class 6, -kubwa takes the class 6 form:

• makubwa = large / big / high for class 6 nouns

So:

• matumizi ... ni makubwa

Even though English may use high, Swahili uses the adjective based on -kubwa.

Yes, -kubwa literally means big, large, or great. But in context it often means:

• high
• large
• considerable
• significant

With things like consumption, cost, loss, or numbers, Swahili often uses -kubwa where English prefers high or large.

So matumizi ... ni makubwa is naturally understood as:

• the consumption is high not just
• the consumption is big

A close breakdown is:

• Matumizi = usage / consumption
• yaliyokadiriwa = estimated
• ya umeme = of electricity
• ni = is/are
• makubwa = large / high

So the structure is roughly:

usage estimated of electricity is large

More natural English: Estimated electricity consumption is high.

Yes, that is also understandable and natural.

Both versions work:

• Matumizi yaliyokadiriwa ya umeme ni makubwa
• Matumizi ya umeme yaliyokadiriwa ni makubwa

The difference is mostly one of phrasing and emphasis:

• the original sounds a bit more like a compact formal noun phrase, estimated electricity consumption
• the second can sound more like the electricity consumption that has been estimated

In many contexts, both are acceptable.