Adding solar PV to your structure typically will not lower your natural
gas bill, just your electric bill, but one does have the opportunity while
sizing the solar PV system to make changes to how you use energy that
will lower the natural gas bill. If you know that your gas hot water
heater is on its last legs you may want upsize the solar PV system
slightly and replace the gas hot water heater with an electric hot water
heater that uses your free clean solar electricity to produce potable hot
water. Or if you have cold rooms that your gas furnace can never quite
keeps warm enough to feel comfortable without turning up the entire
home’s thermostat to compensate use portable electric heaters in those
rooms, turn down your furnace temperature, upsize the PV system and
then you will be able to lower your home’s natural gas bill.