Grammar · N4
〜ている vs 〜てある
Compare an ongoing/resulting state with an intentionally prepared result.
In short
〜ている can describe an action in progress, a habitual action, or a resulting state depending on the verb. 〜てある commonly describes a state that exists because someone intentionally performed a transitive action.
How it works
窓が開いています can mean the window is open. 窓が開けてあります suggests someone has opened it and left it that way for a purpose.
Useful contrast
The distinction interacts strongly with transitive/intransitive verb pairs and with what is marked by が.
Examples
電気がついています。
The light is on.
資料が机に置いてあります。
The materials have been placed on the desk (ready).
Common pitfall
Do not translate both mechanically as English “is -ing”. Japanese aspect describes different event/state structures.