Kami memasak di rumah supaya lebih hemat.

Kami means we, but it is exclusive: it does not include the person being spoken to.

So Kami memasak di rumah... means We cook at home..., where the listener is not part of we.

By contrast, kita is inclusive and includes the listener:

• Kami memasak di rumah = We cook at home (not including you)
• Kita memasak di rumah = We cook at home (including you)

This is a very common thing English speakers need to get used to, because English we does not make this distinction.

Masak is the base word and can mean to cook or cooked, depending on context.

Memasak is the verb form meaning to cook.

The prefix meN- often forms active verbs in Indonesian. With masak, it becomes memasak.

Compare:

• Saya suka memasak. = I like cooking / to cook.
• Nasinya sudah masak. = The rice is already cooked.

So in your sentence, memasak is clearly the action to cook.

No, that is completely natural in Indonesian.

Memasak can be used without an object if the object is obvious, unimportant, or general. It simply means to cook in a general sense.

So:

• Kami memasak di rumah. = We cook at home.
• Kami memasak nasi di rumah. = We cook rice at home.

Both are correct. The version without an object is just more general.

Di rumah means at home or in the house, depending on context.

Here:

• di = a preposition meaning in / at / on
• rumah = house / home

So di rumah is a location phrase.

A useful comparison:

• di rumah = at home
• ke rumah = to home / to the house
• dari rumah = from home

Also note the spelling:

• di rumah = correct, because di is a preposition
• dirumah = incorrect in standard spelling

Supaya means so that, in order that, or so.

It introduces a purpose or intended result.

So the structure is:

• Kami memasak di rumah = main action
• supaya lebih hemat = purpose/result

Other common words with a similar meaning are:

• agar = also so that, often a little more formal or neutral
• biar = can also mean so that, but is often more casual

Examples:

• Kami memasak di rumah supaya lebih hemat.
• Kami memasak di rumah agar lebih hemat.

Both are natural.

Because Indonesian often expresses this idea more simply than English.

Lebih hemat literally means more economical / more thrifty / more cost-saving.

After supaya, Indonesian often leaves out words that English might include, such as we can be or it will be.

So:

• supaya lebih hemat = so that it’s more economical / so we can save more money

You could make it longer:

• supaya kami lebih hemat
• supaya menjadi lebih hemat

But in everyday Indonesian, the shorter supaya lebih hemat sounds very natural.

Not exactly.

Hemat means something like:

• economical
• thrifty
• cost-saving
• not wasteful

It is about using less money, energy, time, or resources efficiently.

It is not exactly the same as murah, which means cheap / inexpensive.

Compare:

• Makanan ini murah. = This food is cheap.
• Memasak di rumah lebih hemat. = Cooking at home is more economical / saves more money.

So hemat focuses on saving, not just low price.

It can be, but Indonesian often omits the repeated subject when it is already clear from context.

So these are both natural:

• Kami memasak di rumah supaya lebih hemat.
• Kami memasak di rumah supaya kami lebih hemat.

The first one is more concise and very common. The subject kami is understood automatically.

This happens a lot in Indonesian: if something is obvious, it is often left unstated.

Yes. Indonesian word order is flexible in many cases.

The most neutral order here is:

• Kami memasak di rumah supaya lebih hemat.

But you could also say:

• Supaya lebih hemat, kami memasak di rumah.

That puts more emphasis on the purpose: To save money / To be more economical, we cook at home.

Both are correct. The difference is mostly about focus and style, not basic meaning.

Supaya is very common and natural in everyday Indonesian. It is not wrong or too informal here.

Agar is also very common and may sound slightly more formal or written, but in many situations they are interchangeable.

So both are good:

• Kami memasak di rumah supaya lebih hemat.
• Kami memasak di rumah agar lebih hemat.

If you are speaking normally in daily conversation, supaya is perfectly fine.

Yes, in theory hemat can refer to being economical with different resources, such as:

• money
• electricity
• time
• fuel

For example:

• hemat listrik = save electricity
• hemat waktu = save time

But in Kami memasak di rumah supaya lebih hemat, the most natural interpretation is saving money. The context strongly suggests that cooking at home is cheaper than eating out or buying prepared food.