One Year of Experience with Geothermal
We have just completed all the arithmetic for the first year of operation with geothermal in our new home. Our home replaces a smaller 50-year old home on the same lot. The old home had 4 inch fibreglass batt insulation retrofitting in some but not all walls and R28 fibreglass blown into the attic. The new home has an excellent air seal, 2x4 walls insulated with fibreglass batts, and R40 blown-in fibreglass in the attic. The new home has a high efficiency pleated filter, humidifier, and a UV sanitizer in plenum. The old home had the standard $5 fibreglass pad filter in the air handler for the furnace, and no other enhancements.
The old home was 2050 SF on 2 floors; the new one is 4771 on 3. The new home has aircon and an ERV, the old one had neither. The new home has electric hot water augmented by the geothermal system, the old home had natural gas furnace and hot water. The old home had 2 direct vent gas fireplaces, the new has one. Our climate is very similar to Seattle's.
Total energy cost in the old home was $140 per month (average of last 12 months in the home) while energy in the new one cost us $130 per month (average of first 12 months in the home). If we adjust these costs for the price increases in electricity (up 9%) and natural gas (up 7%) that occurred after the old home was demolished but before we moved into the new home, the price comparison is even more favourable. Before building we estimated the payback period for our geothermal unit at 8 to 12 years, depending on the rate of price increases for electricity and natural gas. That calculation still looks about right with the first year of energy costs known.
The geothermal system has functioned flawlessly after an initial glitch caused by a refrigerant leak that was found in the unit when first started up after installation.