How to calculate energy savings of a new furnace?
The first thing you need to do to calculate energy savings of your new gas furnace is to determine the actual cost of heating your home. Your gas bill is filled with extras such as delivery and surcharges and also the energy used to heat your water. A simple way to break these “extras” out is to use your gas bills from the last 12 months. First take the 3 summer months, June, July and August, and add them up, next divide by 3 to get the average monthly bill in the non-heating season and multiply by 12 to establish how much is spent on natural gas for the whole year on everything except the furnace. Now add up all 12 monthly gas bills and subtract the amount that you figured above for the 12 months of other appliances. This gives you a good idea on what you spent on just space heating for an entire year.
Now if your furnace is 25 years old it probably has an efficiency rating of 55% AFUE. That means about 55 cents out of every dollar heats the house and 45 cents goes up the chimney. The new high efficiency furnaces are 95% efficient so only 5 cents out of every dollar is wasted out the vent.
Say your last year’s gas bill for just space heating that you calculated above was $2250.00. This may be a common amount in Alberta.
$2250.00 – ($2250.00 x 55%)/95%= Savings/year
$2250.00 – (1302.63) = $947.37 Savings/year