By far the quickest and cheapest way to get from Alor Setar to Butterworth (Penang Sentral) is to take one of the trains operated by KTM (Keretapi Tanah Melayu Berhad).
Services on this route are KTM Komuter Utara trains (northern commuter) which are a really cheap way to travel in this part of Malaysia, with regular services starting in the early morning and running until fairly late in the evening.
The long-distance ETS trains no longer operate from Alor Setar to Penang Sentral (Butterworth).
(Jadual KTM Komuter Alor Setar ke Butterworth)
To see the latest KTM Komuter Utara train timetable, please click on the following link:
If you want to travel in the other direction from Butterworth to Alor Setar:
The duration of the train journey to Butterworth (Penang Sentral) from Alor Setar is one hour and 8 minutes which is much quicker than taking a bus (plus, the bus station in Alor Setar is located quite a distance from the centre of the city, while the train station in Alor Setar is located within 10 minutes walk of the centre).
(Harga Tiket KTM dari Alor Setar ke Butterworth)
The ticket price for these trains is only 7.10 MYR making it the cheapest way to travel to Butterworth from Alor Setar.
As Komuter trains are just like Subway or Tube trains you get in the west, there is no need to make an advance booking (unlike ETS trains).
Just go to the station ticket counter, buy your tickets, then take the next train.
These commuter trains can get quite busy (especially during the rush hour with people travelling to/from work) so avoiding these times will mean you are more likely to get a seat.
Arriving at Butterworth:
The train station in Butterworth is just a few minutes walk away from the Penang Sentral terminal building where you can take a bus to just about anywhere in Peninsular Malaysia, or take the ferry over to Penang Island (Pulau Pinang).