Hello Sharon, a flight from the UK to Cuba is approximately 10 hours long, and you can expect the temperature in Cuba to be a very nice mid/high 20s.
To my knowledge, powercuts are not all that frequent, we certainly don't get many stories from our customers about them. However, if you are worried then you could pack a torch as part of your luggage, should a powercut actually occur in the evening.
Regarding Malaria tablets, I would recommend that you contact your GP to advise you on such matters.
I hope this information has been helpful and if you have any further queries then feel free to email me.
Kind regards
James, your editor