Selecting the best-suited HVAC system depends on factors such as cost and availability of the energy source; appliance or system efficiency; cost to purchase, install, and maintain the appliance or system; and environmental impacts associated with the fuel. Energy prices tend to vary somewhat by geographic location because of availability of fuel type and supply, market pressures, production capacity, weather, season, and politics. A common way to compare heating energy costs is by determining the delivered heating cost, expressed in consistent units (i.e., $/MMBtu or $/GJ), based on the cost of the fuel ($/unit), heating value of the fuel (HV), and seasonal efficiency of the system or appliance (η_hs) expressed in decimal form (i.e., 80% = 0.80):

A client is considering heating systems for a 2400 ft2
residence anticipated to have an annual heating load of 90 MMBtu/year. Compute the annual cost of heating the building with these systems:
a. A modern, high-efficiency furnace with a seasonal efficiency of 96% that is fired with natural gas with a heating value of 103 000 Btu/CCF and a cost of $1.50/CCF.
b. A modern, high-efficiency furnace with a seasonal efficiency of 92% that is fired with fuel oil with a heating value of 140 000 Btu/gal and a cost of $3.50/gal.
c. An electric-resistance furnace with a seasonal efficiency of 100% that is electrically powered with a heating value of 3413 Btu/kWh and a cost of $0.15/kWh.
d. An air source heat pump with a seasonal efficiency* of 150% that is electrically powered with a heating value of 3413 Btu/kWh and a cost of
$0.15/kWh.
e. A geothermal heat pump with a seasonal efficiency* of 350% that is electrically powered with a heating value of 3413 Btu/kWh and a cost of $0.15/kWh.

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Delivered Heating Cost ($/MMBtu) = ($/unit 1 000 000 Btu/MMBtu)/(1hs. HV) Delivered Heating Cost ($/GJ) = ($/unit - 1 000 000 kJ/GJ)/(nhs HV)