For more than 100 years utilities have supplied electrical power to customers and have done so with good reliability. The principle is simple. Loads may do as they wish. They may be random or intermittent and generally are not individually monitored by the utility. Generation, on the other hand, MUST be both dispatchable and monitorable, and electric system operators must be able to manage the real and reactive power from a generator.
Historically, utilities have become very adept at managing generation capacity to maintain a continuous balance between supply and demand. But today, the world is faced with a need to reduce or even eliminate carbon emissions, which complicates the supply-demand balance. Most electricity in the US, for example, is generated by burning fossil fuel. This needs to change, along with change to the electricity supply system and the direct customer use of fossil fuel. We are looking to remove the steady performers, and to replace them with supplies that are intermittent and perhaps random, all the time maintaining a balance between supply and demand.