First off, there may be a bit of confusion that needs to be cleared up. Are you looking to produce hot water or are you looking for a load to reject waste heat? An absorption chiller will use waste heat and provide a heating load and give you cold water. If you are looking to produce hot water, which is what it sounds like from your post as your alternative is a boiler, I don't think an absorption chiller is what your after.
In any case, I would seriously have second thoughts about an absorption chiller. They tend to be *VERY* maintenance sensitive and require a lot of care and feeding. If not handled properly, they also have short life spans. If you have a decent cooling load, most of the time, with a constant need for hot water, you may want to consider a heat recovery system using an electric chiller. A typical system will produce hot water at ~1.2KW/ton, which may be less than your boiler costs, with the benefit of getting cold water as a side effect. The overall efficiency and cost if you need both heating and cooling can result in a substantial savings. You can also gain better efficiency if you run the chiller at a lower condenser temperature and may be better off overall to use it as a preheat for a boiler system. The other thing to consider is that if you need a cooling load for your cold water in order to make hot water with a chiller.
