I tried
String serverPath = "http://api.openweathermap.org/data/2.5/onecall?lat=" + mLat + "&lon=" + mLon + "&exclude=minutely&lang=de&appid=" + owmKey;
and got for the size of the JSON String
Size of answer is 18035.
While the same request with excluded hourly gives
Size of answer is 4585.