I guess i don’t understand why it’s wasting more energy than would be wasted by running a separate hot water heater.
I don’t have gas close to the places i need hot water (except the washing machine, i suppose, since the gas dryer is next to it) and i don’t really have room to add much in or near the bathrooms. I don’t think point-of-use water heating is practical, given the existing walls and infrastructure.
If you are comparing it to a separate water heater installed somewhere close to the furnace, the difference is going to be pretty small. A water heater and a boiler furnace are both going to release heat into the house. My furnace is in a well-insulated room in the basement with the door always closed, and that room does not get noticeably warmer than other rooms in the basement during the summer. The hot water pipe coming off of the furnace is slightly warm, about the same as you’d expect from a water heater. The baseboard water heat pipe coming off of the furnace is cool, so any heat leaking out through that is minimal.
I would say that the difference in energy cost between a combination boiler furnace and a separate water heater is going to be negligible in the grand scheme of things.
On the other hand, if I had a separate water heater, I could expect to go through three or four water heaters over the lifetime of the furnace (the furnace is designed to last about 40 years, modern water heaters seem to only last about 10 to 15 in my experience). That is a rather significant cost.
If you are comparing a boiler furnace to point-of-use water heaters, from a thermal efficiency point of view the point-of-use heaters will certainly be better. From an overall cost of use though, the additional installation cost, especially in a house that doesn’t have the infrastructure for it, is going to far outweigh the energy savings over the life of the system.
It’s also worth noting that I am using my modern-ish (15 year old) boiler furnace for comparison. The original 1960 boiler furnace was nowhere near as well-insulated and it did heat up the entire room in the summer.
Also, my furnace is a conventional cast-iron furnace. It’s not one of those fancy-shamncy condensing furnaces linked to above. I have no experience with those.
I have no need to fit a furnace in an apartment closet, and i doubt I’ll end up with a fancy schmancy condensing furnace, either.
It will live in the utility room in the basement, and either vent through the existing chimney or through a new vent that might be installed for it.
I don’t know how much heat is released by a gas water heater but my electric heater releases very, very little. Of course there’s no exhaust and burner chamber, the electric elements are completely internal. Water heaters are usually more efficient than boilers at heating water, they’re properly scaled and the boiler body itself is not getting heated up and eventually releasing that heat into the house.
OTOH, they’re making fancy high efficiency stuff these days, maybe they’re reduced these problems to insignificant levels. My experience is with traditional equipment, a little better insulated and more efficient burners, but still basic technology that’s at least 50 years old.
My boiler is literally a water heater. A large, expensive water heater. It might be that because it’s larger it’s less efficient than a smaller hot water heater. But i bet that new boilers are built to higher standards than me got water heaters, just because it’s a bigger-ticket item.
Anyway, i don’t think i can do solar, and electric heat is a lot more expensive than gas, so i plan to stick with gas.
I’m not recommending electric. I think gas will be a much better deal for a long time. I wish there was a gas line on my street. And it sounds like you understand the options, I’m sure you’ll work out the best solution.
I do not recommend tankless water heaters. My summer gas consumption is $10 per month, 90% of that is hot water. A tankless system might save me $3 a month during the summer. For the other nine months, the heat dissappated by the water tank helps the basement temperature. In my bedroom, it takes 20 seconds for hot water to arrive from the tank. At my son’s house (with tankless), it takes an additional 30 seconds for the tankless system to get up to speed. Running two showers, laundry, and a dishwasher at the same time is not a problem with an 80 gallon tank. All this convenience is well worth the $10-$12 extra that I pay per year.