Hi there
In December it was going dark just after 6pm. Main streets are quite bright but I can't remember if it was street lights or just the lights from the shops etc. If your hotel is a bit off the beaten track you will need a torch. We also found that its a lot harder to get a taxi after 11pm. Most seem to have stopped working by then.
Towpal

It gets dark around 6 - 6.30, a small torch is a pretty good idea in some places as the street lights (if any) usually consist of a fluorescent stuck to a pole.

we noticed street lights were all over in candolim well they were flourescent tubes you had years ago in your kitchen

I had a mini tourch i brought last year which was godsend as we had a lot of powercuts when i was there due to the squall !! I would definatly recommend taking one.

It's dark at 6. There are street lights but the electric supply is always on/ off so you would be well advised to take a torch (or better yet buy one there).

Definitely recommend a torch. In fact last year we even had a guy on the beach selling them so there you go!

i think its part of the fun stumbling home during a power cut or even when there's not one