Annual Heating Costs

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:

$C o s t o f H e a t i n g = (116.53 M M B T U s) \times \frac{$ 24.77}{M M B T U s} = $ 2, 886.44$

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

$C o s t o f H e a t i n g = (116.53 M M B T U s) \times \frac{$ 10.50}{M M B T U s} = $ 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.

A c t u a l E n e r g y C o s t = \frac{F u e l C o s t (\frac{$}{U n i t o f F u e l})}{H e a t i n g V a l u e (\frac{M M B T U s}{U n i t o f F u e l}) \times E f f i c i e n c y}

$Actual Energy Cost = \frac{\frac{$ 0.88}{C C F}}{\frac{0.1 M M B t u s}{C C F} \times 0.90 (Efficiency)} = $ 9.80 / M M B t u$

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.

$Heat Loss from Walls = \frac{1, 248 f t^{2} \times 10, 500^{o} f - d a y s \times \frac{24 h}{d a y}}{13.0 \frac{f t^{2}^{o} f h}{B t u}} = 24.19 M M B t u$

$Heat Loss from Roof = \frac{1, 150 f t^{2} \times 10, 500^{o} f - d a y s \times \frac{24 h}{d a y}}{29.0 \frac{f t^{2}^{o} f h}{B t u}} = 9.99 M M B t u$

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

= 24.19 + 9.99 = 34.18 M M B T U s

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

$= (34.18 M M B t u s) \times \frac{$ 9.80}{M M B t u s} = $ 334.96$

Example

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