30 year old furnace

[RH]

I have a 30 year old gas furnace that heats my house. It's not very efficient though (maybe 40-50% efficient) . A new 80% efficient one cost $1900 installed. We spend $600/yr on gas (furnace is our only has appliance ). Should I pull the trigger and upgrade? We plan on being in the house 5-7 years. If we sold the house , a buyer would ask for a new furnace for safety reasons, etc... I'm not too interested in 95% furnances right now.

[MikeBear]

Is this natural gas, or propane?

Either way, a 30 year old furnace can be outright dangerous, and $1,900 for a new one is a good price, if that's the installed price. I had my 15 year old furnace replaced in 2005, but that was because it exploded due to a gas pocket. Blew the chimney right off the roof, and into the woods. Luckily the furnace contained itself, and didn't do any damage to the house.

[alsoknownasDean]

If if halves your gas bill, then you've got a payoff period of just over six years, and you're planning on staying five to seven years.

From a cost perspective, it's pretty much lineball, but from a safety and environmental perspective (especially considering the existing unit would be 36 years old by then), I'd lean towards replacement.

Then maybe keep it a couple degrees lower to get the bills lower still :)