Q: Should I replace my 21 year old natural gas boiler and water heater with separate units like I have now, or should I consider a combination unit that handles both space heating and domestic hot water in one? I’ve been quoted $8400 for a boiler only, and $9200 for a combination unit.
A: At 21 years old, you’re wise to think about replacement. Combination units are becoming more popular and they work well. On the other hand, one nice thing about having a separate boiler for heating, and a separate water heater for domestic hot water is an increase in overall reliability. If your boiler goes down, you’ve still got hot water. If your water heater goes down, you still have space heat. With a combination unit, you’ll lose both if the system fails.
Another thing to think about is cost. Have you ever considered going with a heavy duty tank-style water heater that’s also rated for space heating applications, instead of a combination boiler? I know the Polaris tank-style heater is made especially for dual application (heating and domestic hot water) and it costs $4k the last time I checked. That’s less than half of the quote you received for a combination boiler that would do the same job. Click here for a detailed technical article, video and schematic diagram about using the right kind of tank-style water heater for space heating. A surprising number of people, even professionals, say you can’t use a tank-style water heater for heating. They’re wrong because units are specifically made for the job.