kongetu no suidoudai ha omotta yori takakatta desu】【.

It means this month’s water bill or the water bill for this month.

• 今月 = this month
• の = a linker that works a lot like of or an apostrophe-s
• 水道代 = water bill / water charges

So 今月の水道代 literally means something like the water-charge cost of this month.

の connects nouns.

Here, 今月 and 水道代 are both nouns, so の links them:

• 今月の水道代 = this month’s water bill

This is a very common pattern in Japanese:

• 日本の食べ物 = Japanese food / food of Japan
• 昨日のニュース = yesterday’s news
• 私の本 = my book

So in this sentence, の shows that the water bill belongs to or relates to this month.

は marks the topic.

So 今月の水道代は means as for this month’s water bill...

The rest of the sentence says something about that topic:

• 思ったより高かったです = it was higher than I thought

Japanese often structures sentences as:

• [topic] は [comment]

So here:

• Topic: 今月の水道代
• Comment: 思ったより高かったです

Because Japanese often leaves out things that are obvious from context.

In English, you usually need it:

• It was higher than I thought.

In Japanese, once the topic has been introduced with 今月の水道代は, you do not need an extra pronoun. The sentence naturally means:

• As for this month’s water bill, it was higher than I thought.

Omitting pronouns is extremely common in Japanese.

思った is the past form of 思う.

In 思ったより, the idea is than I thought or than expected. Since the thinking is treated as something already formed in your mind, Japanese commonly uses the past form here.

So:

• 思う = to think
• 思った = thought

思ったより is a very common expression meaning:

• than I thought
• more than expected
• than I had imagined

より means than in comparisons.

So:

• 思ったより高かったです = it was higher than I thought

A good way to see it is:

• A より B = B is more... than A

Examples:

• 昨日より寒い = It’s colder than yesterday.
• 思ったより難しい = It’s more difficult than I thought.

In this sentence, the comparison standard is what I thought/expected.

Because the sentence is talking about something in the past.

• 高い = is expensive / high
• 高かった = was expensive / was high

Since the sentence is about this month’s water bill and the speaker is looking back on it, the past form is used:

• 高かったです = was high / was expensive

For bills and prices, 高い often means expensive rather than physically high.

Yes. 高かったです is the polite past form of an い-adjective.

• Casual: 高かった
• Polite: 高かったです

So the full sentence is in polite style because it ends with です.

This is very natural in everyday Japanese.

Here it means expensive.

Literally, 高い can mean high or expensive, depending on context. With a bill, fee, or price, it usually means expensive:

• 値段が高い = the price is high / it’s expensive
• 電気代が高い = the electricity bill is expensive / high
• 水道代が高い = the water bill is high

So in this sentence, 高かったです means the bill cost more than expected.

They are similar, but 思っていたより can sound a bit more explicit, like than I had been thinking or than I had expected beforehand.

• 思ったより = than I thought
• 思っていたより = than I had thought / than I had expected

In many everyday situations, 思ったより is perfectly natural and common.

Yes, that is a very natural translation.

Other natural translations include:

• This month’s water bill was higher than I thought.
• The water bill for this month was more than I expected.
• This month’s water bill turned out to be higher than expected.

All of these capture the basic meaning well.

It can refer to either, depending on context.

More literally, 〜代 often means cost/charge/expense for ~. So 水道代 is the water charge or water bill.

In everyday English, translating it as water bill is usually best.

A natural breakdown is:

• 今月の水道代は = As for this month’s water bill,
• 思ったより = than I thought,
• 高かったです = it was high / expensive.

Japanese often puts the topic first and the main description at the end. The verb or predicate usually comes last, unlike English.

So although the word order feels different, the structure is very normal for Japanese.

That looks like a typo or formatting error.

The sentence should normally be written as:

今月の水道代は思ったより高かったです。

So the strange 】【 should probably be ignored. The standard ending is just です。