Literally, that which can be maintained for a definable period of time, sustainable energy is energy production that can last for the foreseeable future.
Sustainable energy practices must rely on resources which can continue to supply our needs.
These sources must be used cautiously so that they will not be used up, run out, or otherwise become unusable.
Even renewable resources can become unsustainable.
If a resource is used up faster than it can regenerate, it will eventually be entirely depleted despite its renewability.
Conversely, a non-renewable resource can be sustainable if it's used in moderation.
Again, if used without caution, these too may become be depleted in a short time.
For most people sustainable energy use means that the environment is not significantly damaged due to accumulated effects of an energy practice.
This part of the definition of sustainable energy is quite politically charged with widely varying opinions.
Often advocates for fossil fuels will claim that coal, oil and natural gas are sustainable because the reserves for these are so large, discounting the problems with climate change.
All renewable energy sources like solar, wind, geothermal, hydropower and ocean energy are sustainable as they are stable and available in plenty.
While sustainability is a mindset and renewable energy is a method, both are environmentally-focused.
While sustainability is a mindset and renewable energy is a method, both are environmentally-focused.
