Learn Hardcore Indonesian: Kami boros listrik jika lampu dibiarkan menyala. - We are wasteful with electricity if the lights are left on.

kami = we (excluding the listener).
kita = we (including the listener). Here the speaker is probably excluding the person being addressed. If you want to include your listener in the generalization, you can say: Kita boros listrik jika lampu dibiarkan menyala.

Is boros an adjective or a verb? Why is there no “to be”?

boros is an adjective meaning “wasteful.”
Indonesian doesn’t need a linking verb like “to be” before adjectives. So Kami boros listrik literally “We wasteful (with) electricity.”

Do I need a preposition (like “with”) after boros?

No. The usual pattern is boros + resource:

boros uang (wasteful with money)
boros waktu (wasteful with time)
boros listrik (wasteful with electricity)

Can I say memboroskan listrik or membuang-buang listrik instead?

memboroskan listrik is grammatically fine (“to waste electricity”) but is less common in everyday speech than boros listrik.
membuang-buang listrik (“to squander electricity”) is also natural and sounds stronger/criticizing. All are correct; boros listrik is short and idiomatic.

What’s the opposite of boros?

hemat or irit (frugal, economical).
Example: Kita harus hemat listrik.

What nuance does jika have compared with kalau, bila/apabila, and ketika?

jika/bila/apabila = “if” (conditional). apabila is the most formal; jika and bila are also formal/neutral.
kalau = very common in speech; can mean “if/when (whenever).”
ketika = “when” (time, not condition). You could say: Kalau lampu dibiarkan menyala, kami boros listrik.

Can I put the jika-clause first?

Yes. Both are natural:

Kami boros listrik jika lampu dibiarkan menyala.
Jika lampu dibiarkan menyala, kami boros listrik. (Use a comma when it’s first.)

Why is lampu singular—shouldn’t it be “lights”?

Indonesian nouns don’t need plural markers. lampu can mean “light” or “lights” from context. To stress plurality or specificity:

lampu-lampu (lights, plural)
semua lampu (all the lights)
lampunya (the light(s), specific/known)

What is dibiarkan exactly, and who is the agent?

dibiarkan is the passive form of membiarkan “to let/leave (something)”.
Root: biar → membiarkan (active) → dibiarkan (passive).
The agent is omitted (generic). You could add one: … jika lampu dibiarkan (oleh kami) menyala, but it’s usually unnecessary.

Why passive dibiarkan menyala instead of active membiarkan lampu menyala?

Passive highlights the thing affected (lampu) and allows you to omit the doer. Both are correct:

Passive: Jika lampu dibiarkan menyala, …
Active: Jika kami/kita membiarkan lampu menyala, …

What’s the difference between menyala, menyalakan, and nyala?

menyala = to be on/lit (intransitive). Example: Lampu menyala.
menyalakan = to switch/turn something on (transitive). Example: Menyalakan lampu.
nyala = the root/noun “flame/glow” and the base for the verbs. Spelling note: meN- + nyala → menyala.

Is hidup interchangeable with menyala for lights?

Often yes. Lampu masih hidup ≈ Lampu masih menyala (“The light is still on”). menyala is very common for lights; hidup is broader (devices, machines).

Can I say meninggalkan lampu menyala to mean “leave the light on”?

That’s not idiomatic. meninggalkan means “to leave/abandon (a place/thing).” Use:

membiarkan/biarkan lampu menyala (leave the light on)
or express the opposite: jangan matikan lampunya / jangan biarkan lampu menyala (don’t leave it on).

How can I emphasize “left on” as “kept on”?

Add tetap or terus:

… jika lampu dibiarkan tetap menyala.
… jika lampu dibiarkan terus menyala.

How do I negate this idea?

Predicate negation: Kami tidak boros (listrik) jika lampu dimatikan.
Imperative: Tolong jangan biarkan lampu menyala. / Tolong matikan lampunya.

Does this sentence have tense? Could it mean future?

Indonesian doesn’t mark tense by default; context decides. It can be general/habitual. To stress future, you can add akan:

Kami akan boros listrik jika lampu dibiarkan menyala. Many speakers also use jadi for a result: Kami jadi boros listrik kalau lampu dibiarkan menyala.

What does -nya do if I say lampunya?

-nya often marks definiteness (“the/that/its”). lampunya can mean “the light(s)” (already known) or “its light.” Example: Jika lampunya dibiarkan menyala, … = “If the light(s) are left on, …”

Is there a more casual spoken version?

Yes, colloquial Jakarta-style:

Kita boros listrik kalau lampu dibiarin nyala. Notes: dibiarin (colloquial passive of biarin), and nyala used as a bare stative in speech.

Pronunciation tips?

ny in menyala/nyala is one sound like “ny” in “canyon.”
biar in dibiarkan has two vowel sounds: bi-ar.
Stress is relatively even; don’t over-stress any one syllable.