Taking a quick look at the kwh-ng prices you posted your electric is
easily double the cost of Ng. So junk the electric and put in gas. A
relocated tankless Ng unit would save you allot.
I have .12kwh costs and nearly the same for gas, I relpaced a good
modern well insulated electric tank with tankless and my bills went down
75% giving a 4 yrs payback on a 600 Bosch tankless. Look into Rinnai
they are 88% efficient vs 83 for Takagi. You will need the 180000 units
and large gas supplys. Relocate them to where the water goes. Takagi
makes Bosches large unit.

Better would be abandon the in concrete Hw pipe , run new pipe and
insulate it well. The concrete is sucking the heat out of your line and
if it is copper the concrete will ruin it anyway in 40 yrs