EGEE 102
Energy Conservation and Environmental Protection

Annual Heating Costs

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In the example on the page 12, we see that the heat loss from the house (walls, windows, and the roof) was 116.53 MM BTUs. We also know that it costs \$24.77 for 1MM BTUs if electrical resistance heating is used (see Example 17 on page 26). The total cost for the heating can be calculated as follows:

Cost of Heating = ( 116.53 MMBTUs ) ×  $24.77 MMBTUs  = $2,886.44

The price of fuel oil is \$10.50 per MMBtu. The annual heating cost would be:

Cost of Heating = ( 116.53 MMBTUs ) ×  $10.50 MMBTUs  = $1,1223.57

Example

A house in International Falls, MN (HDD = 10,500) consists of 1248 ft2 of walls with an R-value of 13 and 1150 ft2 of roof with an R value of 29. The home is heated with natural gas. The AFUE is 0.90 and the price of natural gas is \$0.88/CCF. What is the annual heating cost?

Energy cost per million BTUs from natural gas can be calculated using the following equation.

Actual Energy Cost =  Fuel Cost ( $ Unit of Fuel ) Heating Value ( MMBTUs Unit of Fuel ) × Efficiency

Actual Energy Cost= $0.88 CCF 0.1 MMBtus CCF ×0.90 (Efficiency) =$9.80/MMBtu

Heat required can be calculated from the heat loss. Heat loss from the house is from two sources: walls and the roof. Heat loss from each of these sources for a year (season) can be calculated by using the following equation.

Heat Loss from Walls= 1,248  f t 2 ×10,500  o f - days × 24 h day 13.0 f t 2   o f h Btu =24.19 MMBtu

Heat Loss from Roof= 1,150  f t 2 ×10,500  o f - days × 24 h day 29.0 f t 2   o f h Btu =9.99 MMBtu

Total heat loss = sum of heat loss from the walls and the roof

= 24.19 + 9.99 = 34.18 MMBTUs

Annual heating cost = Annual heat loss (MMBTUs) x Actual energy cost ($/MMBTU)

=(34.18  MMBtus )× $9.80 MMBtus =$334.96