Thermo Dynamics
112 N Lexington St. Spring Green, WI 53588
Phone: (608) 588-7079   Fax: (608) 588-2267
Email: info@tdhvac.com

Energy Use and Carbon Footprints
BuiltWithNOF

All heating and cooling systems use energy that comes from burning some type of fuel, be it gas, oil or coal.  The only exceptions to this are the various renewable sources such as wind, solar, hydro and nuclear.  However, even these renewable sources still will use fuels for making the machinery and facilities and for transportation.  As such, no source of energy is truly “carbon free”

For homeowners, there are usually three areas of interest associated with using various fuels for heating and cooling systems:  the fuel costs per unit of heating (or cooling), the cost to install the equipment and the carbon footprint of using this energy.

Energy Costs:

As the primary use of energy in Wisconsin is for heating rather than cooling, we will look at that in more detail.  The following table lists the energy available in the various types of fuel:

Fuel Type

Energy Content

Current Price

Cost per million BTU

Propane (gallon)

91,500 BTU

$ 2.29 / gallon

$ 25.03

Natural Gas (CFT)

1,050 BTU

$12.92 / 1000 CFT

$ 12.30

Heating oil (gallon)

138,500 BTU

$ 3.57 / gallon

$ 25.78

Electricity (kWh)

3,412 BTU

$0.10 / kWh

$ 29.31

From this table it would seem that natural gas is by far the cheapest way of heating a structure.  All of the other fuel source have comparable energy costs.  If we now take into account the efficiency of the various heating appliances and use the highest efficiency of these appliances general utilized, we get the results shown in this table:

Fuel Type

Efficiency

Cost per million BTU

Propane

95%

$ 26.35

Natural gas

95%

$ 12.95

Heating oil

90%

$ 28.64

Electrical resistance heat

100%

$ 29.31

Geothermal heat pump (water to water)

COP of 3.5

$ 8.37

Geothermal heat pump (water to air)

COP of 4.5

$ 6.51

(COP is Coefficient Of Performance which is the number of BTU’s of heat output for every BTU of electricity used)

Thus, taking into account the efficiency of the appliance, geothermal heat pumps will have the lowest energy costs.  This is the case because heat pumps do not generate the heat, they just transfer it from one place to another.  In the case of a geothermal heat pump, the heat is transferred from the ground into the structure when in space heating mode.  When in cooling mode, heat is transferred from the structure into the ground.

Carbon Footprint:

While from the above information, it would seem that geothermal heat pumps are the most efficient, one must also look at the “carbon footprint” of using these various fuels.  Each type of fuel has differing amounts of carbon contained in it which is emitted into the atmosphere when it is burned.  While electricity does not have carbon in it, it must be generated somewhere.  In the United States, the largest fraction of electricity is generated by burning coal, followed by nuclear energy

The following table shows the amount of carbon that is emitted by using various types of fuel to generate a given amount of energy:

Fuel Source

Carbon content (Tons / billion BTU)

Propane

17.02

Natural gas

14.47

Heating oil

21.49

Electricity - Coal

64.28

Electricity - Nuclear

0.40

Electricity - Wind

0.37

Electricity - Photovoltaic

4.6

If we take into account the efficiency of the various heating appliances, we will get the following carbon footprints:

Fuel Type

Efficiency

Carbon emitted (Tons / billion BTU)

Propane

95%

17.92

Natural gas

95%

15.23

Heating oil

90%

23.88

Electricity - Coal

100%

64.28

Electricity - Nuclear

100%

0.40

Electricity - Wind

100%

0.37

Electricity - Photovoltaic

100%

4.6

Electricity - Coal

Geothermal COP of 3.5

18.37

Electricity - Coal

Geothermal COP of 4.5

14.28

Electricity - Nuclear

Geothermal COP of 3.5

0.11

Electricity - Nuclear

Geothermal COP of 4.5

0.09

Electricity - Wind

Geothermal COP of 3.5

0.11

Electricity - Wind

Geothermal COP of 4.5

0.08

Electricity - Photovoltaic

Geothermal COP of 3.5

1.31

Electricity - Photovoltaic

Geothermal COP of 4.5

1.02

Thus, from a carbon footprint, any non coal burning electrical method is good.  But since coal based electrical generation provides the largest percentage of electrical power in the United States, resistance heating will emit the most carbon.  Even using geothermal heat pumps with a COP of 4.5, the carbon footprint is only a little better than natural gas.

Costs:

The installation and maintenance costs for propane, natural has and heating oil based systems are very similar.  Electrical resistance heating is somewhat cheaper to install than fuel burning appliances.  The cost of geothermal systems is substantially more that for any of the other systems.  Actual system costs will depend on the exact installation, but will typically add $6,000 to $15,000 to the system cost.  This additional cost must be amortized over the life of the equipment through savings in energy usage.

 

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