There is enough grid scale battery capacity currently online that we can make reasonable projections as to the costs of a grid supplied by non-dispatchable sources such as solar and wind. Not cheap but not impossible.
Not doing deep checking and just grabbing numbers that look reasonable off the internet (eg. lower quality than WikiPedia
):
4 hour rated grid scale battery storage costs $1400 per kW capacity
https://www.nrel.gov/docs/fy21osti/79236.pdf
natural gas costs between $700 and $1200 per kW capacity
solar PV costs about $2600 per kW capacity
https://www.eia.gov/analysis/studies/powerplants/capitalcost/pdf/capcost_assumption.pdf
So a battery is more expensive than natural gas, and can only run for a few hours before it is depleted. PV is also more expensive than natural gas, and has much lower capacity utilization. But now we have enough information for round numbers.
Assume that to supply enough PV energy you need 4x the capacity of your natural gas system, and that to load shift you need 12 hours of battery capacity. So for each kW of natural gas you would need 4 kW of solar capacity and 3kW of battery storage.
In very rough round numbers if you wanted to tear everything down and replace it with solar and battery it would cost perhaps 10x the cost to do the same with natural gas.
The above analysis is _very_ crude, and I am sure any number of this group could rip huge holes in it. I'm just throwing a dart to get a handle on where reality is between 'of course we can do it but it will cost a bit more' to 'so expensive as to be impossible'.
-Jon