I have noticed that some trains have plug sockets installed, presumably for commuters to use to charge their devices etc.
However, some trains seem to have these all over the place, while others have none.
Is there a general rule for which trains and services provide this facility, and can they be used for free? Thinking just UK.
(for bonus) Thinking about services in the EU.
Generally, new and longer-distance trains will, older suburban ones won't. Quite a few have them in first class, but not in standard.
CrossCountry Voyager trains have power available in most seats, and a nice seating plan:
East Midland have power on their 'Meridian' trains but not their HSTs - link
South West Trains don't generally - it appears that some of their carriages do (the non-first-class driving cars of the class 444 units at least), but it's not publicised...
Virgin West Coast
Super Voyager have power at all window seats.
Pendolino First Class have power at all window seats.
Pendolino Standard Class have power at window seats with tables.
Virgin East Coast
Seats with tables have power (all first class seats have tables) link
UK answer.
Fast long distance "intercity" trains and some newer "regional" trains tend to have sockets in the seating areas for the passengers to use, these are usually these are often labeled something like "laptops and mobile phones only" reflecting their intended use. Local and "regional" trains are less likely to have them. There is no charge for using them. The sockets are standard BS1363 ("type G") sockets. Note that the sockets frequently have metal face-plates. Some dodgy travel adapters have been known to cause short circuits when used with metal faced sockets.
Socket locations and quantity vary between train operators and models but as a general rule seats with tables are more likely to have them than those without and seats in first class are more likely to have them than those in standard class. Usually there is one socket for a pair of seats but some older coaches (not sure if any of these are still in service) had one socket per table (a table normally has four seats).
You also get sockets that are not intended for public use and are labeled as such. Often in the back of luggage racks and similar locations. Sometimes people use them anyway and sometimes this gets them into trouble (though from what I can gather most of the time they get away with it). Some of these sockets also have warnings that voltage and frequency may vary......
Some of the most recently refurbished trains have USB charging in addition to the "type G" sockets. It also seems that at least some "EMR regional" trains have USB charging points but not mains sockets.
