Electricity can range from 11¢/kWh to 29¢/kWh in California or higher: https://www.energybot.com/electricity-rates/
Natural gas ranges from (converted) ~ 2¢/kWh to 8¢/kWh in Florida: https://www.eia.gov/energyexplained/natural-gas/prices.php (using conversion factors from https://www.nrg.com/resources/energy-tools/energy-conversion..., which I think assumes 1000 ft^3 ~= 1 therm ~= 29.3 kWh)
So your heat pump's COP has to exceed the ratio between natural gas and electricity in your area to make it cost-effective (or you can get solar + battery backup).
Electricity prices can vary quite a bit, too... in Cali, for example, it's gone up from 14¢ to 24¢ over 16 years, which is nearly double the rate of inflation.
What is the make and model of the thermostat you are using?
Is it from the heat pump OEM (Trane?) or a third party?
It’s a rebranded Nexia
* https://www.bayareaservice.com/wp-content/uploads/2020/02/18...
The process to update the costs (which has to be done a few times per year when my utility changes their rates) is not very user friendly - have to get into the technician menus and change scary looking stuff) but it works quite well.
Gas cost has varied a bunch over the years I’ve had it, electricity less so. But the furnace has only run a few days per year and only when when it’s been (depending on gas cost) below 10 to -5 degrees Fahrenheit.
My heat pump (trane xv19) kicks ass and if I were doing the hvac upgrade again I’d skip the furnace entirely and let the heat pump work a little harder/longer on the coldest days.
It’s damned near always more cost-efficient to run the heat pump. And my shiny new high efficiency furnace will never, ever pay itself off saving me a few bucks a day the three or four days per year that the math works in its favor.