Breakdown of denkidai wo setuyakusuru tame, syouenemoodo ni simasita.
をwo
direct object particle
電気代denkidai
electricity bill
節約するsetuyakusuru
to save (on)
ためtame
for (the sake of); in order to
省エネモード に するsyouenemoodo ni suru
to set to energy-saving mode
Elon.io is an online learning platform
We have hundreds of Japanese lessons and thousands of exercises.

Questions & Answers about denkidai wo setuyakusuru tame, syouenemoodo ni simasita.
Why is the subject missing in this sentence?
Japanese often omits the subject when it’s clear from context. Here (I) or we is implied, so you don’t need to explicitly say “I” or “we” as you would in English.
What does 節約するため mean, and why is ため used here?
節約するため literally means “for the purpose of saving (electricity costs).”
- ため is a noun that marks purpose (“in order to…”).
- After a verb dictionary form you normally use ために, but in more formal or written Japanese you can drop the に and simply write ため followed by a comma.
Could we say 節約するために、省エネモードにしました instead? What’s the difference?
Yes. 節約するために is the more standard spoken form. There’s no real change in meaning—ために is slightly more conversational, while ため (without に) feels a bit more formal or concise in writing.
Why is に used in 省エネモードにしました?
In Japanese, noun + に + する means “to make/choose/set something as [noun].”
So 省エネモードにしました = “(I) set it to energy-saving mode.”
What exactly is 省エネモード?
省エネモード is an abbreviation of 省エネルギーモード (energy-saving mode). You’ll see it on TVs, air conditioners, computers, etc., to reduce power consumption.
Why is を used after 電気代?
Because 節約する is a transitive verb meaning “to save (money/time/etc.).” The particle を marks 電気代 (the electricity bill/cost) as the direct object of 節約する.
Why does the sentence end with しました? Could another verb be used?
しました is the polite past of する (“to do/make”). It shows the action of switching to energy-saving mode is completed. You could also say:
省エネモードに設定しました
using 設定する (“to set/configure”) with essentially the same meaning.