| Many a home owner on the look out for | | | | The next step is to apply each appliance's |
| something new to replace an old, inefficient | | | | efficiency to its respective fuel price. But it's not |
| heating system probably knows a thing or two | | | | as simple as multiplying the fuel price by the |
| about the exceptional efficiency of geothermal | | | | percentage of efficiency (95% or 350%). Instead |
| heat pumps. But few people are aware of the | | | | you would use the coefficient of each percentage |
| new 95% efficient condensing boilers fueled by | | | | as a constant to keep the comparison apples to |
| natural gas. | | | | apples. |
| While a geothermal heat pump's 350% efficiency | | | | The condensing boiler efficiency is 95% therefore |
| far outstrips that of a 95% efficient condensing | | | | the coefficient is 1/.95 or 1.05 |
| boiler, higher efficiency ratings don't always mean | | | | The geothermal heat pump efficiency is 350% so |
| lower heating costs. | | | | the coefficient would be 1/3.50 or.29 |
| It's only when the cost of fuel is factored in can | | | | Finally, the efficiency coefficient is multiplied by the |
| you determine the actual cost of heating for each | | | | cost per therm of fuel for each system to |
| system. In the example below the cost to | | | | determine which one produces 100,000 Btu of |
| produce 100,000 Btu will be used to compare the | | | | heat for the least amount of money. |
| systems. | | | | Geothermal Heat Pump:.29 x $4.19 = $1.22 per |
| Since a geothermal heat pump runs on electricity | | | | 100,000 Btu |
| measured in kilowatt hours (kWh), and a | | | | Condensing Boiler: 1.05 x $0.78 = $0.82 per |
| condensing boiler is fueled by natural gas | | | | 100,000 Btu |
| measured in therms, it's necessary to convert | | | | The surprising results show that even though a |
| kWh of electricity into "therms" to make an | | | | geothermal heat pump is 3½ times more |
| accurate comparison. | | | | efficient than a condensing boiler the heat it |
| One therm of gas produces 100,000 Btu so we | | | | produces is 49% more expensive. |
| need to know how many kWh of electricity it | | | | This paradox is brought about by recent low |
| would take to produce 100,000 Btu. Since one | | | | natural gas prices and the high cost of electricity |
| kWh = 3,413 Btu it would require 29.3 kWh to | | | | in New England. |
| produce 100,000 Btu, or one "therm" of electricity. | | | | Depending on where you live, utility rates will vary |
| Here in New England electricity goes for $0.143 | | | | from the ones used in this example but it should |
| per kWh. So a "therm" of electricity would cost | | | | be simple enough to substitute local rates for the |
| $4.19 (29.3 x $0.143). A therm of natural gas, | | | | ones here to make your own comparisons. |
| according to National Grid, retails for $0.78. | | | | |