opinions on cold start

Steve McCarthy_2

Hi folks,
I heat my house for the most part with wood. I have a steel, Axeman-Anderson boiler in the basement for indirectly heating my hot water and for heat when I am away or when I can't get out of bed in the morning and stoke the wood stove. The boiler is direct vented and fired with a Riello. I now use about 250 to 300 gallons of oil per year. My building heat load is 38,500 BTU's in a 7700 degre day heating climate.
I would like to start heating my domestic water with the sun. Presently, the only thing that keeps my boiler warm is the daily firing to heat my water. If I start heating my water with the sun, it is likely that my boiler will make a lot more cold starts when its cloudy or I can't get out of bed.
Is this situation likely to lead to premature boiler death? Is there a low cost solution? Is a cast iron boiler more resistant to the condensation that occurs on a cold startup?

Thanks Steve McCarthy