I post this as I have some real-world experience with this type of conversion.  Quebec Canada mandated that all oil furnaces be replaced by heat pumps, and this impacted my retired in-laws.  As they could not find any source for heating oil, they reluctantly had the old furnace removed and had a new heat pump installed. 

During their first winter, they found that the warmest room in the house was in the basement due to the equipment for the heat pump.  They found that the second-floor bedrooms were not receiving enough heat and took to using more blankets and even wearing a knit cap during the coldest weather. To help remedy the problem, they looked at adding additional insulation and installing siding over the second story brick outside walls.

In the end, it cost them tens of thousands of dollars, all of it from their retirement funds. 

While subsidies may be available with the California plan, where does the money come from?  The government?  No, the government does not produce anything of value in the open market.  It comes from TAXES. So, the old law of government is proven:

The government creates a problem, then to solve the problem they create a bureaucracy which needs to be paid for by raising taxes.  In some places, this is called (excuse the French) a circle jerk.

https://www.city-journal.org/article/californias-heat-pump-fantasy