Should I go to electric hot water

I currently have my HW supplied through a tankless coil in my boiler. This requires year 'round running of the boiler.

I realize that oil BTUs are cheaper than electric ones, but, are they when you figure in the losses associated with firing the boiler year around?

Also, I have a mixing valve which I believe needs cleaning/replacement soon as the shower temps seem to be fluctuating lately.

I was thinking of adding an electric water heater downstream from the tankless coil and eliminating the mixing valve. This would allow me to shut down the boiler for maybe 6-7 months a year and still benefit from the efficiency gains of the tankless coil heated water when the boiler is running.

My concerns are with the boiler sitting cold for extended periods. The boiler is a 4 section smith cast iron, about 10 years old.

I will be doing the install work myself as I am comfortable with pipe sweating and electrical work. So installation labor costs are not an issue.

Using a boiler to heat water in the summer just adds wear to the unit. Letting it sit 'cold' isn't a problem, even though it won't really be cold since its summer. If you want efficiency gains in the summer only, check out those hybrid HWHs. They pull heat from your house and use it to heat water. It's like having an air conditioner too!

I still haven't used one...but I'm waiting to hear feedback.