How to use 40lb Propane tanks in a residential hook up

It's possible, but unless your furnace is way over sized, you can't just stick a heavier box in the same packaging and burn wood in it. You can reuse the duct work and blower, but everything else would need to be replaced. Depending on how much heat you need, it may not make sense to place the fire box where your furnace is. Further more, you may want to keep the propane as a back up. Don't discount how convenient it might be once in a while to turn a valve, strike a match, turn a switch and have instant heat.

Heating 100% with wood in any cold climate takes a huge volume of wood. If you don't plan for easy transport of fuel from storage into the firebox, as well as good storage convenient to vehicle access, the scheme is doomed. Because of this, many serious wood burners have a boiler system to move heat from the firebox to the air handling unit (or directly to radiators). It's much easier to move heat stored in a fluid than to lug blocks of wood through the house and up and down stairs.

Consider carefully if you're ready for this. Every part of wood burning is dirty, hard work. When you factor in all the costs and effort, propane can be a competitive alternative. Another option many people take is to leave the HVAC system and install a wood stove in the main living area at a central location. The wood stove is capable of heating much of the house. The HVAC system is used to keep the outer rooms heated. This will typically involve re-balancing the duct system and moving the thermostat.

There's a lot of different possible solutions, what's best will depend on climate, house size, lifestyle, personal habits and preferences, etc. Locate contractors that specialize in wood fired heating systems, not just simple stove installations. It takes someone with that experience to make a reasonable recommendation based on your particular situation.

First, check to see if there are any tax breaks on the LP system for your area.

My rule of thumb on energy savings savings is, it must pay off in less than 10 years or half of it's usable life (which ever is shorter). Since you have to replace the unit, see if the difference in cost - expected savings in energy over 10 years justifies going LP. A lot of times, the energy efficient items don't pay off unless they have a tax break or you have to replace an entire system anyways.

Edit: I was curious about the results and looked up the values. Assuming you are using 800 gallons of oil each year at a rate of $4.21 a gallon = $3368 year. You would need 1060 gallons of propane to match the 800 gallons (taking into account different efficiency) at a rate of $3.80 a gallon = $4028 a year.

Cost data came from here: http://www.eia.gov/dnav/pet/pet_pri_wfr_a_EPLLPA_PRS_dpgal_w.htm BTUs of propane: 91,500 per gallon BTUs of heating oil: 135,000 per gallon Conversion from oil to propane used: oil gallons * oil BTUs * oil efficiency = 92,880,000 effective BTUs used each yet. 92,880,000 / propane efficiency / propane BTUs = 1057.38 gallons of propane used.