House: 90 years old
System Description: In a closed loop piping system, water is pumped 300 feet underground, where it takes on the 55 degree underground temperature. It is pumped back into the basement to a heat pump unit with a set of copper coils containing a refrigerant that has a very low boiling point. Contact with the 55-degree water makes the coolant boil, and the resulting heat is pumped through the house as forced hot air heating. In summer the system runs backwards. The heat pump puts heat from the house back into the water. The water is pumped underground, where it releases the heat and returns to a 55 degree temperature.
Components: Two vertical 300-foot wells, piping, heat exchanger, pump, air ducts
System provides: 100% of home heating, 100% of home cooling (Electricity is used to pump water and distribute warm/cool air.) No hot water is provided. Oil hot water heater is used.
Previous heating and cooling system: Oil furnace, forced air. 2 window air conditioners
Installation: Fall, 2009 by Gray Co. Plumbing, Heating and Air conditioning. Bedford, MA www.graycompany.net
Town permits involved: Yes. About 9 sign-offs needed.
Price: $34,000 minus $10,200 federal tax rebate = $23,800
Price included replacement of leaky air ducts. System eliminated the need to replace the oil furnace.
Payback Period – about 6 years, including amount saved for not having to spend $10,000-$12,000 to replace furnace and air conditioning. Savings: about $1,900 per year for reduced oil expenditures.
Advantages:
- Heat pumps are efficient because they transfer existing heat rather than burning fuel to make heat
- Provides heating and air conditioning in one efficient system with existing ducts
- House is cleaner with no oil or natural gas being burned to heat your home
- Geothermal heat is warm, not hot heat, so it doesn’t dry out your house in winter
- Geothermal air conditioning removes more moisture than a typical central air system because it has more capacity (the size is set for the heating needs)
- Geothermal systems operate most efficiently when kept at near constant temperatures so even though we’re saving significantly on heating we keep the house warmer than we used to both day and night
- Although the system is expensive to install, about ½ the cost is for the wells which won’t need replacement even when the furnace does
- Our “carbon footprint” is lowered beyond our reduced energy use because electricity sources are getting greener and oil isn’t.
- The price of oil is going up, while the price of electricity has been stable.
Disadvantages:
- Cost of upfront installation.
- Remaining challenge to heat areas furthest from the furnace (family room addition)
- Air blows more loudly than oil system.
