Either mini-splits or variable speed heat pumps are the way to go.
From December 2021 through September 2022 electric bill, my HVAC bill has ranged from about $30-50/mo for the kwh of electricity alone plus a fixed service fee add-on. Tennessee Valley Authority is the electricity producer, largely hydroelectric and nukes, lowest cost technologies.
One outdoor heat pump and two indoor exchange/blowers hanging on the wall. Each indoor unit has a variable speed blower, a programmable thermostat, motorized vanes to direct air up/down and left/right and an option to use a sensor to adjust the thermostat a few degrees higher or lower if no one is in the area. The outdoor unit has variable speed motors on its fan and compressor. Legacy central air components completely removed leaving only the blocked off floor registers.