Location when on home wifi is wrong; can I disable using known wireless networks to get location?
I suppose Android is recognizing the WiFi router with it's MAC address. Since this is not easily changeable on most routers (you could do so with a custom firmware like DD-WRT), you can set your Android to use only GPS as a location source as a workaround.

Depending on your Android version, you should be able to do that under  Settings - Security &amp; Privacy - Location - Mode. Set it to Device only.

Please note that this disables location determination via mobile network so you might experience your GPS being used more often and the accuracy being lower when you're inside a building.