Short Answer
The family calculates annual savings from heating using an old furnace ($144) and a new furnace ($172.8). Ultimately, they face an annual cost increase of $28.8 when switching to the new furnace.
Step 1: Calculate Savings with the Old Furnace
To find out how much the family saves by using the old furnace, we multiply the annual usage of energy by the cost per therm and the efficiency of the furnace. The formula is:
- Savings on Old Furnace = 600 therms * $0.30/therm * 0.80 (efficiency) = $144
Step 2: Calculate Savings with the New Furnace
Next, we calculate the savings when using the new furnace, which operates more efficiently. Again, we multiply the annual energy usage by the cost per therm and the new efficiency rate:
- Savings on New Furnace = 600 therms * $0.30/therm * 0.96 (efficiency) = $172.8
Step 3: Determine Total Annual Savings
To find the family’s total annual savings in heating costs, we subtract the savings of the old furnace from the savings of the new one. This will tell us if there are any savings or additional costs:
- Annual Savings = $172.8 (new furnace) – $144 (old furnace) = -$28.8
Thus, the family experiences an overall cost increase of $28.8 annually in heating expenses.