Comments on: How much natural gas would I use after converting from oil?

By: Is it safe to use a portable gas cooker in the house for cooking, just for a short time.?

Mon, 26 Apr 2010 16:01:41 +0000

[...] How much natural gas would I use after converting from oil? [...]

By: gatorbait

gatorbait — Sun, 25 Apr 2010 14:29:18 +0000

Not really.

Your best bet would be to call 3 or 4 HVAC contractors to give you bids for a gas fired furnace to replace your oil burning unit.
They will base their bid on the type of construction of your house and the internal volume of your house and the area in which you live.
A typical 90% efficient gas furnace with a 100,000 BTU heating capacity would probably cost you $3500 to $4500.
A typical 80% efficient gas furnace with a 100,000 BTU heating capacity would probably cost you $2000 to $3000.
I just installed a new 80 % efficient unit to replace my 28 year old 80% efficient gas furnace. The 90% efficient unit would never have paid for the difference in cost between the two units when you consider that the 90% efficient furnaces do not last as long as the 80% efficient units, and are more prone to breakdowns.

The average heating value for heating oil is about 140,000 BTU/Gallon.
Your oil fired furnace is probably about 60% efficient, so you are probably getting only about 84,000 BTU/Gallon of output from it.
Each Therm of natural gas =100,000 BTU and each Therm of natural gas varies in price depending on where you live, but ours is going to be costing about $1.25 per Therm this coming winter.
Multiply the number of gallons of heating oil you use by 84,000 to get the total amount of heat that you need, then divide that by 100,000 to get the number of therms you will use and then multiply that by $1.25, and then divide that by either 0.90 or 0.80 depending on the efficiency of your new furnace.

By: Chandramohan P.R

Chandramohan P.R — Sun, 25 Apr 2010 14:29:18 +0000

You can calculate the factor by knowing the calorific values of Oil/Gas.

By: Tony Q

Tony Q — Sun, 25 Apr 2010 14:29:18 +0000

the unit used in the metering for gas consumption is cuft, for oil is gal
assuming oil furnace eff is 60%
you want to know how many X cuft of gas to heat the same house using Y gal of oil

the heat content of gas is 1030 Btu / cuft
the heat content of oil is 138,500 Btu / gal

X cuft = [(cuft) / (1030Btu*0.90)][(138500Btu*0.60) / Y (gal)]
X cuft = 89.64 / Y gal
to obtain X cuft of gas, plug in the Y gal of oil you used

since you know how much gal of oil used, you could find out the Btu required to heat the house, approx same Btu is required to install central air conditioning. its good to have statistic data. insulate your house then check the fuel consumption see how much further saving

in case you want to know the saving, the last time i know
cost of oil #2 in us is $2.50/gal
cost of gas in us is $9.00/1000cuft