Better alternatives to "Save me!" - meaning to save electricity

I suppose conserve would be a more correct (or at least less ambiguous) term for what's meant.

But as I said in the comment, "Save me!" is a bit funnier and draws your attention as it personifies the electricity (or the light switch) a little, like it's asking for your help as well as asking you to save electricity.

Save me is fine because it does not necessarily only mean to save something or someone from something.

If you look at the Oxford Dictionaries Online definitions for save, you'll see five definitions including the following:

Keep safe or rescue (someone or something) from harm or danger.

• ‘they brought him in to help save the club from bankruptcy’

The definition above fits the save from context

The definition relevant to the save electricity context is actually:

Preserve (something) by not expending or using it.

• ‘save your strength till later’

I would say "save me" is fine in English. It ends up as somewhat of a pun, which doesn't translate well and might have been unintentional, but I don't think that detracts from the message.

It's common in English to talk about "saving electricity" or saving some other resource like money. This is listed as definition 4 of Save on dictionary.com:

to avoid the spending, consumption, or waste of

This works fairly well, and is extremely common in English. The only point for potential confusion is that the label is on a switch, so it could come across more as "save the light switch" rather than "save electricity". This is also where the double-meaning comes in; this interpretation invokes definition 1 or 2 instead:

1. to rescue from danger or possible harm, injury, or loss
2. to keep safe, intact, or unhurt; safeguard; preserve

In this context, the object is being personified and asking for help in some way. "Save me!" without any indication as to what they might need saving from is perfectly acceptable in English, though it does imply that there is some kind of danger that exists.

For a fluent English speaker, I think "Save me!" is fine and the dual interpretations are likely to be clear enough to understand, while the slight pun and personification will make the message more memorable and eye-catching. However, since the message is intended for a "bilingual school" it's possible that the double-meaning will be more confusing than it is worth. An alternative would be the more unambiguous "Save electricity!" which dodges the second meaning arising from "me". A shorter version could be "Save power"; it seems awkward to me, but it's comprehensible enough.