They do. They use power from the grid, of which a significant and increasing fraction is wind and solar (and hydro.)
It doesn't often make sense for factories to have their own power sources, because their power draw varies during the day, while solar and wind output also varies. So they'd need a huge amount of overcapacity to ensure that there's always enough power. The grid is the efficient way of averaging out all the supply and demand fluctuations so the supply is used as efficiently as possible.
This is why the grid has a hard time kicking Solar City homeowners off the grid: they produce dirt-cheap power at peak consumption times. Anyone who remembers the California rolling blackouts (thanks Enron, et al) understands that power consumption peaks in the mid afternoon.
At the same time, homeowners understand why they need to be on the grid: they are at work during the day and run their appliances in the early mornings and evenings when their own solar panels are less than optimal.
Thus the power purchase agreement is the deal that makes sense.
> Anyone who remembers the California rolling blackouts (thanks Enron, et al) understands that power consumption peaks in the mid afternoon.
That's not true. Power consumption tends to peak around 1900-2100, while solar energy production will peak around 1300-1500. The typical load profile is that you have a minimum load around 300 that ramps up to a peak around 900-1200, then plateaus/slowly declines until about 1600-1800, ramps up to a second, higher peak around 1900-2100, and then declines rapidly to the 300 minimum. Exact times and amounts will vary depending on time of year and the local weather and climatic concerns: A/C-heavy summer climates will see an earlier peak consumption and much less of an intra-day climb, while cold winter climates will see later peak consumption with a more prominent higher evening peak.
The extra fun thing that kicks in is that northern climates tend to have minimum solar production during the time of year when energy consumption is highest (winter!), while southern climates tend to have maximum solar production during peak energy consumption. The economics of solar power are quite different for California versus Massachusetts, let alone places such as Alaska.
A larger issue for electric companies is staying on the grid is slowly starting to be a bad deal for home owners. A minimum electric bill with zero usage covers the electric grid and administrative costs etc. It’s normally not much, but ever cheaper solar and battery systems are competing with that same electric grid.
This varies by area, but could quickly become a death spiral over much of the US.
It doesn't often make sense for factories to have their own power sources, because their power draw varies during the day, while solar and wind output also varies. So they'd need a huge amount of overcapacity to ensure that there's always enough power. The grid is the efficient way of averaging out all the supply and demand fluctuations so the supply is used as efficiently as possible.