"Hello Friend"

Id contact each utility company, gas and electric in your area...and
have THEM convince you with documentation/calculations which is best to
go with.

In general, someone else doing your work for you will only convince you of
what will make them the most money.

1 kilowatt-hour = 3412.142 BTU
1 Therm = 100,000.4 BTU

Some bills charge you for therms, ie, heating value of gas actually
delivered to the house. Make sure to include that.

Derate the K-watts/BTU's/Therms by the general efficiencies of the furnace.

Electric - generally close to 100%, however I'd use 95-100% or so depending
on the condition of the unit.
Gas - generally less than 80%. 70% if older, 90+% if very new and well
installed.

The rest of the info you need is on your utility bill and the faceplate of
the furnaces. This will get you in the ballpark.

I have a newer 90,000 btu furnace running at about 90%.

The other inefficiencies of what actually gets transferred to the house
through your ventilation will be present in both systems, so can be ignored.


- Nate