Solar heat from a sunspace can be 100 times cheaper than PVs per peak watt,
and houses need several times more heat than electrical energy.
$00 might buy 200 ft^2 of "solar siding," eg a thermosyphoning air heater
with 4 12'x4' pieces of R2 Thermaglas Plus twinwall polycarbonate with 80%
solar transmission. In full sun (250 Btu/h-ft^2) on a 30 F day, you might
collect 200 Btu/h-ft^2 of 150 F air and lose (150-30)1ft^2/R2 = 60, ie 140
net (41 watts), at $/41 = $.073 per peak watt. The 7.9 kW output could
heat a house and water for showers, with the help of a $5 car radiator and
its 12 V 20 watt fans and a $0 13-gallon 1`x300' pressurized plastic pipe
coil in a polywood tank with a folded EPDM liner.
Ohm's law for heatflow is just Ohm's law for electricity with different units.