Heat pump water heaters are drastically more energy efficient. Also, there are immediate air quality improvements from not burning fracked gas in your home. Also, recent research has shown that methane leaks happen far more than previously realized at every stage of the natural gas ecosystem, from initial extraction to pipelines to refining to residential usage, and every gram of methane is equivalent to something like 30 grams of CO2, so you need to consider the massive savings in warming from reducing that systemic leakage.

Finally, it's important to get these processes started immediately. It's still going to take decades for this policy to result in the millions of houses updating their equipment, and we might be down to a far smaller percent of grid power coming from fossil fuels by then.