How to keep electricity running consistently in Tropico 5?

I build 5 - 6 power plants at center of my island and those small square power units to spread electricity all over the island. I build mine over all coal deposits to provide coal to the power plants.

At first, the power plants run properly, but then gradually in few months, power outages increase. Most of the times, only 2 out of 6 power plants are generating putting country in red.

I am planning on exporting coal via trade routes. Will it help me??

Well, same as in real world, you should invest in diverse array of energy sources!

• Build wind mills (expensive, no workers)
• Build geothermal plants (cheaper, needs workers)
• Build wave-powered plants (cheapest upkeep, needs workers)
• Build a nuclear power plant (moderate cost, needs workers)

Also you may:

• Increase budgets and/or assign managers (depending on your constitution policies +managers/+budget)
• Import coal/natural gas with power plant upgrade.
• Check logistics - fuel can be stuck in mines/ports and you may be short teamsters.

In my personal experience 1 power plant, 1 nuclear plant and a couple geothermal/wind/wave power plants can sustain a population up to 2000 tropicans given stable supply of fuel and employees.