'Baseload' is a commonly misunderstood term that refers to the minimum electricity demand used by one or more consumers at any one time, over a period of time.
To illustrate the point simply, imagine you have a car garage with a beer fridge inside. The demand for electricity in that room will vary as you turn the lights on and off, use the electric door, and plug power tools into the power points. But the demand in that room will never drop below the minimum requirement of the fridge, which runs 24/7. So that fridge is setting the baseload of that room.
At an individual scale a single device like a fridge can set the baseload but at scale the grid's baseload is set by our collective requirements.
What is commonly misunderstood about baseload power?
'Baseload' is a commonly misunderstood concept. The fundamental mistake that people make is to think of baseload as a supply-side concept rather than a demand-side concept. This is incorrect. The baseload is the base (i.e. minimum) load (i.e. demand) for electricity over a period of time.
When incorrectly conceived of as a supply-side concept, the term is often misused by categorising power plants as either 'baseload generators' or 'not baseload generators.' The implication is usually that some generators (e.g. wind and solar) cannot always meet our electrical demand while others (e.g. nuclear and coal generators) can.
This is half true. It is true that wind and solar generators are intermittent. But it is untrue that this is a problem. Though at any one time some wind or solar generators may not be working, overall wind and solar (and energy storage systems) can still meet baseload because they will be built in quantities and networked together in a way that fuel-based generators are not.
What are our options for supplying our load?
There is no type of electricity generator that naturally produces electricity in a way that perfectly matches demand. Our demand for electricity constantly changes—often quite randomly—and it is often dramatically volatile. As a result the government constantly monitors demand and frequently intervenes with supply, to ensure that supply and demand are kept in perfect balance.
There are two basic systems that can match an ever-changing load. For the sake of simplicity, we will call them the 'minimum-plus' system and the 'maximum-minus' system.
The minimum-plus system is what we have had historically and continue to have today. It is a system where generation is designed to meet minimum demand and additional generators turned on as required. The maximum-minus system is what we will have in future. It will be a system where generation is designed to exceed maximum demand and generators turned off as required.
Changing from one system to the other is no small feat, however, the maximum-minus system will ultimately be much cleaner, faster, and more affordable than our current minimum-plus system.