Within the past few years, solar+batteries is starting to win bids against new natural gas generation in many common peak-related situations (not all yet, but increasingly so). The expectation is that solar+storage will win most peak-related bids by 2025 and then win most baseload bids by 2035.

https://www.woodmac.com/press-releases/batteries-renewables-...

After that, it will likely start to displace existing natural gas similar to what it's doing for coal now.

https://www.forbes.com/sites/energyinnovation/2018/12/03/plu...

You can draw a scenario. Natural gas has to be distributed, either as gas in pipes or as power down lines. Solar can, theoretically, be generated closer to source. Play with the geography enough and you can say that solar is the cheaper option.

Another common way to game the number is to compare the price of installed solar per watt using only generic land prices. A natural gas generator can be installed anywhere. A solar panel needs a southern view, preferably on a south-facing slope, to maximize exposure to direct sun. In my area (BC, Canada) our combination of higher latitudes and mountains mean that solar's land requirements are very specific/expensive in comparison to natural gas generators. Also weather.