Ground Source Heat Pumps, or more commonly referred to as geothermal heat pumps are one of the most talked about heating and cooling systems in the consumer market today. Consumers are excited about the incredible energy savings that can be had by installing one of the most efficient heat pumps on the market. The problem you ask? Most contractors and homeowners don’t understand this “new technology” and the benefits they can get by installing geothermal. I will give you some history of the technology and some tips for selecting the right contractor for the job.
Ground source heat pumps have existed for well over 60 years. There is a myth of it being a new technology, the truth is, it is just misunderstood and some HVAC contractors just choose to not install them for fear of how they actually work, or don’t have the knowledge to design it. These systems can achieve energy efficiency ratios (EER) of 41, and a coefficient of performance (COP) of 5.3. The higher the numbers the less money you spend running it, similar to the gas MPG of your vehicles. Air source heat pumps cannot reach 50% of that efficiency and don’t perform well when the temps drop in the single digits. The rate of return on most ground source heat pumps is 3-10 years or sooner with the benefit of tax incentives or power company rebates. These rebates change yearly so be sure to research these costs as they can save you thousands off the initial investment.
The key to selecting the right contractor for your ground source heat pump is to make sure they are designing the system properly. Otherwise, the expected energy savings may not be attained. Make sure installing contractor does the at a minimum calculations called: Manual J and Manual D. Manual J is a calculation which determines the heating and cooling loads on your home based off your homes orientation, outdoor design temperatures, R-Values of the building shell, interior loads, and window performance. Don’t be afraid to ask your contractor for a copy of this Manual J load calculation report. If your contractor doesn’t ask questions about those design values, he may not be sizing it correctly. Manual D takes the design a step further, and designs the ductwork for optimum velocities and pressures needed for correct air delivery. This calculated by using design parameters from the equipment’s blower performance charts and pressure drops on the duct system. Don’t be afraid to ask your contractor for a copy of the Manual D calculation report. The final crucial step for a high performing geothermal system is to ensure the water loop field is designed correctly. Your contractor designing the well systems must research and understand soil types and the ability of the soil to transfer energy. Rock and clay type soils hold more energy therefore the loops may be shorter. Sandy soils absorb less energy therefore your loop field will need to be deeper or more loops may be added.
If done right on new construction, geothermal systems can reduce the HERS score by up to 25 points. With current tax incentives and rebates, they typically cost $4000-$6000 more than a high performing standard system can pay for themselves in less than 5 years.