1. Under what conditions is converting to geothermal heating & cooling the most economically attractive?
Several factors play a part in determining the cost of installation and the annual energy savings which together determine how quickly your investment is going to pay you back.
- The amount of heat required to maintain a comfortable indoor temperature is largely determined by the size of the heated space and how airtight and well insulated the space is. Large leaky and/or poorly insulated homes will have higher the heat loads, resulting in the greater energy savings from conversion to geothermal.
- Current fuel type and unit cost is often the most significant factor. Natural gas is relatively cheap (per unit of heat) so the savings will generally be less than if you’re currently heating with propane, oil, or electric resistance. As fossil fuel prices increase, the savings from geothermal, which runs solely on electricity, will generally increase as electricity prices are historically more stable than fossil fuel prices.
- If there is enough open space adjacent to the building so that the ground loop can be installed in trenches or a sufficiently large pond is nearby in which to immerse the loop, the upfront cost of installation will be thousands of dollars less than if the ground loop has to be installed in vertical wells.
- If the existing heat distribution system does not require modification to accommodate the geothermal system, the upfront cost of installation will be less. Generally, forced-air ductwork and radiant floor systems will not require accommodations, whereas baseboard or stove heating likely will.
- If you need to replace an aging furnace/boiler or need to install new heating system (e.g. new construction), then the economic comparison between fossil fuel and geothermal becomes one of incremental (rather than total) cost of a geothermal system.
If most of these factors line up in favor of geothermal, the payback could be as little as two years. In the last couple years, many banks have made available equity-based loans with terms to 20 years; these make it possible have a system installed with no upfront investment and often the energy savings exceeds the repayment installments, enabling the project to be immediately cash flow positive.
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2. How long does it take to convert an existing heating system to a geothermal system?
- Typically, installation of the ground loop (and penetration to your basement) will take one to three days depending on size and ground conditions.
- If no modifications to the inside distribution system are required (see FAQ#1), replacement of your existing furnace or boiler, connection to the loop, and final commissioning to bring the system online will usually take two to three days.
These two steps, depending on scheduling, can sometimes be accomplish concurrently.
3. How does geothermal heating work?
Cold water is warmed by recirculating it through a network of pipes buried in the ground or at the bottom of a pond, after which it passes through a heat pump located inside to extract its heat and reduce its temperature before it returns to the outside piping network to be reheated. This portion of the system is commonly referred to as “the loop”.
The heat pump uses refrigeration technology to concentrate the heat extracted from the loop, which increases its temperature to greater than 100oF. Now it can be used to heat the air or water which is distributed throughout your house via your existing distribution system (e.g. forced-air duct work, radiant flooring, hydronic baseboard). In forced-air systems, the process can be reversed to provide air conditioning.
For a more in-depth explanation, see https://lakecountrygeothermal.com/geothermal-heat-pumps-and-ground-loops/.
4. Does geothermal require a backup heat source?
No, unlike air-sourced heat pumps which dramatically lose efficiency as the outside air temperature drops, necessitating a back-up source of heat, the heat source for geothermal (aka ground-source) heat pumps is at least 6 feet below the surface and unaffected by local weather conditions.
However, back-up heat is commonly employed with single- or two-stage forced-air geothermal (commonly referred to as water-to-air) heat pumps. In this application, the heat pump is purposely undersized relative to the heat capacity required during the heart of the winter, so that it can be better matched to the heat required during the shoulder seasons, reducing the cycling frequency which reduces system efficiency and creates addition wear on the heat pump. Electric resistance heating coils are integrated into this configuration to provide auxiliary heat when needed – when outside temperatures dip to their lowest.
5. Can geothermal heat my potable hot water?
Yes. There are a few different options depending on the specific situation.
6. Do geothermal systems require more maintenance than fossil-fueled furnaces and boilers?
No. In fact, the loop and heat pump – the major components that set it apart from fossil-fueled systems – require almost no maintenance. For more details, see https://lakecountrygeothermal.com/maintenance/.
7. What happens to a geothermal system when the power goes out?
The system will not operate. This is also true of modern furnaces and boilers which utilize an electric igniter to turn them on.