You are right you need to run numbers, but what makes that...

You are right you need to run numbers, but what makes that virtual power plant idea attractive is that you offset the cost of the batteries at each solar-producing location by avoiding the cost of a power plant. I can guarantee you - with the lower level of competition for industrial components and engineering and construction costs for any plant - that any large-scale utility plant will cost many more times the capital cost of batteries storing an equivalent amount of energy installed to a home. *IF* building a new utility plant can be avoided, it is highly likely that the system saves capital expenses, while simultaneously saving 30% of the transmission losses and adding additional features and lower cost for the users.