Keeping a boiler hot all year to provide hot water is not particularly efficient. An indirect WH is often a good choice, but not all boilers can stand cooling off in between calls for heat on the indirect, and still must idle at a moderate temperature. A modern mod-con will cost a good deal of money. If you have natural gas available, it might work out to just add a traditional gas WH and shut down the boiler for the summer. One thing most people do not realize is that the state of the art on heat pumps has evolved so that they can often be a great alternative to older methods and would provide a/c as well. It would help if you related what brand/model you actually have in place. Chances are, it is significantly oversized, and there may be some add-on controls that could help make it more efficient. The first step is to figure out what your actual heat loads are. There are lots of threads here that describe how to get a reasonable WAG based on oil use, boiler efficiency, and heating degree days. Your existing boiler is probably 2-3x oversized for your needs, and this alone is likely a big part of the expense - the more oversized, the less efficient primarily because it will often short-cycle.