I live in Chicago in a 2300 sq ft ranch. The home was built in 1955, and has the original boiler, which was converted from oil to natural gas. Although the boiler is working fine, I wonder about replacing it as the cost of natural gas keeps going up. The efficiency of the new boilers must be far greater than the current one.
How would I go about figuring out if replacing the boiler makes sense? Is there a payback formula I can use? I do not plan on moving for 20 + years.
Also, the newer boilers have the ability to replace the hot water heater with a tank directly attached to the boiler coils. Is this something to consider if I replace the boiler?
Finally, I have seen tankless water heaters. If I am replacing the water heater (9+ years old, 40 gallon), what consideration should I give to the tankless water heater? Is it more efficient to use than a tank, or a tank conneted to a newer style boiler?

Thank you in advance for your time.

Flickit

...heaters...no other present inexpensive technology (including a boiler with a water tank rolled in) compares to the energy savings that come with the on-demand heaters gas heaters.

My daughter and son-in-law went from being nearly in debt to a now comfortable economic lifestyle after I installed one of these to replace the electric they had. These also easily outperform gas types.

Use this in your evaluation.

labman

I think most of the older systems ran about 60 percent efficiency. That means for every 100 btus going into the water, you burned about 167 btus of gas. Replace it with a modern 80% unit and you will use 125 btus, which should reduce your bill to about 75% of what is was. It is possible that a unit converted from oil to gas would be even less efficient. You can buy higher efficiency units, 90 or even 95%. They are more expensive, and tend to have higher maintenance costs.

I have looked at the numbers, and my figures don't add up for the tankless water heaters. They also have a very high original cost. My daughter recently installed a gas tankless hot water heater. I intend to compare gas bills this summer. I think our bill with a gas dryer and a conventional gas hot water heater only runs about $15 a month in the summer with a $10 minimum. Now how long will it take to pay off a $1500 hot water heater with the savings? The tankless units are smaller, but need so much clearance that they can't be located closer to the point of use. Thus you still run the same gallons of heated water down the sink while waiting for hot water to reach the faucet. You can buy conventional water heaters with better insulation and better heat transfer for much less than the tankless ones.

Dig back through this site. There have been several hard to solve problems with the hot water loop in the boiler. I would stick with one of the more efficient, separate, gas water tanks. Mine is over 20 years old and still working fine. I do drain water out the bottom now and then.

Skip the hype in the sales lititure, and read the goverment ratings on hot water heaters.

Flickit

...are that expensive. Don't recall the brand name but wasn't a Bosch and the cost was far less. Unit was engineered in Germany and manufactured in Poland. Someone once told me they ran into the tankless unit in a hotel in Europe somewhere during the 70's. While there are arguments against using these, the cost will eventually come down and the technology improve making it less attractive to own a large reservoir of hot water.

Name of brand was Termet: http://www.go4elite.com/home.htm