If you are out of your house and willing to know if you left your wifi router powered. Or to be more specific, if you want to know if there is electricity in you room then you can get that information from the ISP.
Generally your ISP provides you with login creds to their customer service panel. There you can see if your subscription has expired or how much volume is remaining.
There must also be showing the user status; it means your internet device whose MAC you have bind with ISP is currently active or not. Like
It also shows you when was the router switched off