I'm envious, at 900 pesos I have a mental image of a fan and a single light bulb hanging from a wire.
I lived in a nice apartment in Colinas del Oeste in west Santo Domingo that was 26K a month which is a very nice area.
I moved to a comparable sized apartment in San Cristobal for only 12K a month and negotiated no yearly increases with the owner.
It is a nice 1st floor 3/2 1st floor apartment so it stays fairly cool anyway. I live alone and work so the A/C runs from 5pm to 5am weekdays and 24 hrs Sat and Sun when I'm home.
I have two 12K inverter A/C's, a 43" Flat TV, a 10' projector TV, a stacker washer/dryer, Frigidaire reefer, and inverter Microwave and a Mabe non-electronic gas stove and a 5 gal water heater set very high which means I use little hot water with cold mixed in to lower the temperature when I take a shower and have low volume showerheads.
I only use one light bulb at a time. I have my reefer full of containers of water that I remove as needed to add food. That keeps it from cooling air that's lost every time I open the door.
My A/C's are set at 78 degrees. I only use one at a time so no keeping rooms cold just for the sake of keeping them cold.
I wash 4 loads of clothes once a week. Most of my food is prepared on the gas stove.
It takes some effort, but I think the savings are well worth it.