Concept explainers
HVAC We can estimate the cost CN (in dollars per million Btu) of a natural gas–powered heating system using the formula
where T is the cost per therm of natural gas and E is the operating efficiency of the system. Similarly, we can estimate the cost CA (also in dollars per million Btu) of an air-source heat pump using the formula
where K is the cost per kilowatt-hour of electricity and R is the efficiency rating of the pump. Assume the following:
- An existing natural-gas heater is 92% efficient. (Use 0.92.)
- A new air-source heat pump would have an efficiency rating of 9.5.
- Electricity costs $0.09 per kilowatt-hour.
What would the cost of natural gas have to be to make the two annual costs the same?
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