The electricity supply in Cuba is an interesting mix of 110v/60Hz, 220V and maybe something in between. Both the flat 2 pin and round 2 pin plugs are used.
Before travelling to Cuba buy a Surge Protected Worldwide Travel Adapter with a 6A Fuse. These types of devices or adapters do not convert voltage. You can buy these online or at the airport, at a cost of around £11.99/€16.86/US$18.72/CAD$23.57/AUD$24.92
Surge protection shields your electrical equipment from damaging spikes whilst travelling. (Spikes and brown outs are common in Cuba.) Most come with built-in 6A fuses, safety shutters, AC 110 or 240V inputs and adapters for the UK, Europe, Americas, Japan and Australia.
As I am living here and not just visiting I have experienced many different situations with power. On the whole there are few problems, but I would advise not to leave electrical devices plugged in and then left unattended. Additionally, I would not charge laptops or similar devices or watch TV during electrical storms as most buildings don’t have lightning protection.
There are power cuts, not black outs. Power cuts are isolated to local apartments, blocks or areas and last between 1 minute and a few hours. Blackouts would cover a whole city, which has not happened for a few years.
Showers – It is normal for some showers in Cuba to have electrical cabling on display leading from the showerhead to a fuse breaker. It is usual for sparks, accompanied by loud noises, or a type of electrical arcing to happen when using switches located on the top of the showerhead. Don't worry! This is normal for Cuba. It adds to the sense of adventure and nothing has happened to me or anyone I know – yet! More people slip in the shower while worrying about the electrical cabling!