The combination of heating load, energy source and equipment efficiency determines the annual cost of heating.
If you are heating with gas and are thinking of converting to a more efficient gas heating system, you may be interested in calculating the savings you could expect. Using Table 1 (on page 49) and the following formula will provide you with reasonably accurate figures. You need to know your annual fuel cost and the type of heating technology you are using. (Note: the published AFUE for propane-fired appliances is based on firing with natural gas. This rating should be adjusted in accordance with the footnotes to Table 1 to arrive at a more accurate rating for calculation purposes.)
Example: How much would you save by changing from a conventional gas furnace to a high-efficiency gas furnace at 96 percent efficiency if your present annual gas cost for space heating is $800?
The seasonal efficiency of the new condensing furnace is 96 percent,and the efficiency of your present gas furnace is 60 percent.Hence, A =96 percent, B =60 percent and C =$800.
Thus, you would save $300 a year in energy costs by installing a high-efficiency gas furnace, and you would also eliminate the need for a chimney.
Gas Heating Appliances –Features and
|Condensing boiler 2,3||
|Conversion burners for oil equipment1||
|Direct-vent wall furnace1||
HEATING COSTS WITH DIFFERENT ENERGY SOURCES
You may be interested in calculating the cost of heating with gas compared with the cost of heating with other energy sources, such as electricity, propane, oil or wood. If this is the case, you can use the following procedure (Steps 1 to 4). You need to find out the cost of the energy sources you want to compare and the types of heating technologies you might want to use.
Call your local fuel and electricity suppliers to find out the cost of energy sources in your area. This should be the total cost delivered to your home, and it should include any basic cost that some suppliers might charge, along with necessary rentals, such as a propane tank. Be sure to get the prices for the energy sources in the same units as shown in Table 2. Write the costs in the spaces provided. If your local natural gas price is given in gigajoules (GJ), you can convert it to cubic metres (m3) by multiplying the price per gigajoule by 0.0375. For example,
$5.17/GJ 3 0.0375 = $0.19/m3
|Energy Source||Energy Content||Local Price|
|Natural Gas||37.5 MJ/m3
|Propane||25.3 MJ/L||$0. _________/L|
|Oil||38.2 MJ/L||$0. _________/L|
|Electricity||3.6 MJ/kWh||$0. _________/kWh|
|Hardwood*||30 600 MJ/cord||$_________/cord|
|Softwood*||18 700 MJ/cord||$_________/cord|
|Wood Pellets||19 800 MJ/tonne||$_________/tonne|
Choose the type of equipment you want to compare from the list of appliance types in Table 3 on page 52. Note the efficiency figures in the column titled "Seasonal Efficiency." By using these figures, you can calculate the savings you can achieve by upgrading an older system to a newer, more energy-efficient one or by choosing a higher-efficiency appliance that uses an alternative energy source.
If you know your bill for space heating and the unit cost of your energy source, you can determine your annual heating load in gigajoules from the following equation:
For example,you have been able to determine that your annual bill for space heating with natural gas is $687, gas costs $0.22/m3, and you have an old conventional gas furnace with a seasonal efficiency of 60 percent (see Table 3).
The energy content of natural gas is 37.5 MJ/m3 (see Table 2).
If your bills also include tap water heating and even equipment rentals, you can still calculate your annual heating load, but it will require a little more care and calculation to separate your heating-only portion.
If you cannot get your heating bills, you can estimate your annual heating load in gigajoules from Table 4 on page 53 by selecting the house type and location that is closest to you.
% of Base1
tap water condensing
|Oil||Cast-iron head burner (old furnace)
|Flame-retention head replacement burner||70–78||14–23|
|High-static replacement burner||74–82||19–27|
|New standard model||78–86||23–30|
|Integrated space/tap water
|Electric furnace or boiler||100|
|Air-source heat pump||1.7 COP2|
(ground-source heat pump)
|Conventional stove (properly located)||55–70|
|"High-tech" stove3 (properly located)||70–80|
|Advanced combustion fireplace||50–70|
||Old Detached||New Detached||New Semi-Detached||Town-house|
Old detached – approximately 186 m2 (2000 sq. ft.)
New detached – approximately 186 m2 (2000 sq. ft.)
New semi-detached – approximately 139 m2 (1500 sq. ft.)
Townhouse – inside unit, approximately 93 m2 (1000 sq. ft.)
The annual heating cost is calculated as follows:
The result should give you an approximate heating cost for your house. If you know your actual heating costs and the type of heating system you have, you can modify the heating load originally taken from Table 4 to suit your specific house.
Sample Calculation: You have an old detached home in Edmundston, and you would like to find out what the annual heating cost would be with a high-efficiency condensing natural gas furnace at 96 percent efficiency with gas costing $0.18/m3. The house heating load is 120 GJ (see Table 4), and the energy content is 37.5 MJ/m3 (see Table 3).
If you would like to compare this heating cost with that of other types of heating systems or energy sources, replace the numbers in the formula with the appropriate ones for your comparison using Tables 2 and 3.
Source: Natural Resources Canada (NRCan) - Office of Energy Efficiency