Many zoo facilities will not run unless they are powered, therefore maintaining a power supply is essential to maintaining a functioning zoo.
A power source will power anything that touches its radius, even if the object or habitat is only partially within it. Power facilities will deteriorate and lose efficiency over time; transformers are more resilient to deterioration than wind turbines, while solar panels are the least durable.
Once a power facility's efficiency reaches 50%, its effective radius will start to shrink. This may mean that they stop powering critical facilities and these in turn will fail. When the efficiency rating reaches 0%, the power system will fail completely.
There are a number of ways to provide power for your facilities.
Transformers
Relatively cheap to build and have a large functional radius, but are a non-renewable source of energy and have a running cost based on the number of items they are powering. Guests are not impressed by seeing transformers and will become unhappy if they meet the eye; place them away from sight to avoid this.
Wind Turbines
A renewable energy source that’s more efficient in windy, colder climes. They cost more to purchase than a transformer, but incur no running costs. Guests understand the benefit of wind turbines, but they are noisy and so they still incur a small happiness penalty.
Solar Panels
A renewable energy source that's more efficient in warmer, sunny climates. Like Wind Turbines, they cost more to purchase than Transformers but don't have a running cost. Guests understand the benefit of Solar panels so they're neutral to their presence.
Both forms of renewable energy will help boost the zoo's conservation rating.