seems like it’s around 0.5-1% of total capacity 😔, but still poggers 
edit from real source https://en.granma.cu/mundo/2025-11-13/chinas-cooperation-with-cuba-in-the-energy-sector-remains-strong-and-steady
The official launch of Mártires de Barbados II was led by the First Secretary of the Party’s Central Committee and President of the Republic, Miguel Díaz-Canel Bermúdez, and it is now connected to the SEN, as are its 5 MW counterparts built in several provinces, with a combined generation capacity of 35 MW. Following the completion of this phase, the second stage, already underway, is expected to be completed by next April and will include 13 5 MW PSFV and two 10 MW PSFV, with a total power of 85 MW and batteries to store 20% of the generation produced.
that would put maximal capacity at 3% which is mega pog 
probably at utilization rates of 1-1.5%, depending on batteries and transmission
And the ecological disaster that follows from smelt fish landing on it!