Vertical Geothermal Systems in Seattle

We’ve been seeing allot of interest in Vertical Geothermal Systems lately in the City. Because horizontal system require a large area of available land, most sites within City limits aren’t feasible for less costly horizontal systems. I’ll start off by explaining the main differences.

Horizontal Geothermal Systems rely on loops buried 4-6 feet below the surface of the ground in a horizontal pattern (shown below). An average 2,000 square foot home requires a minimum of 3,500 square feet of land area to support the heating and cooling load. Most City lots cannot support this system, though it is economical to install.

Vertical Geothermal Systems in contrast rely on vertical loops installed in wells that range between 100-300 feet in depth (shown below).An average 2,000 square foot home requires a minimum of 4 wells at 250′ in depth. Well must be placed 10-20 feet apart. Though wells don’t take up allot of space, drilling rigs typically take up about 600 square feet of land space, and require a path that is a minimum of 10′ wide to move around.

Another variation of a Vertical Geothermal System is an open loop well. An open loop system utilizes an existing water well and pumps water through the Geothermal System for heating and cooling. Open loop systems can be more economical to install, and can be very efficient, however, they are restrictive. You must reject the water that passes through the Geothermal Heat Pump. This is typically done by drilling a relief well where the water is discarded to an underground reservoir. This isn’t difficult to do, but we are restricted to 5,000 gallons per day of flow. This restricts the size of Geothermal System that can be installed to 25,000BTUH. Many energy efficient homes can be heated with this size of System, but older homes will generally require a backup source of heat.

The main driver of cost in Vertical Systems is drilling. Drilling costs can range between $14/FT all the way up to $30/FT in our experience. Where horizontal loop systems can be installed for $8-12K for a 2,000 square foot home, vertical loop systems will generally run $20-40K to install.

It is possible that Vertical Systems can still have a 10 year or better payback with your Federal Tax Credit of 30% however. If you are interested in having your site assessed for feasibility, please call the office to set up an appointment for a Geothermal Designer to visit.

Thank you,

Mitchell Mechanical, Inc.

Mitchell Mechanical staff are certified by the International Ground Source Heat Pump Association for installation of Geothermal Systems. We are one of the most experienced company’s in the city at installing Geothermal Heat Pumps, and have many satisfied clients dating back to 2007. We have tackled many different applications including integration with Radiant Floor Heat, and Solar Thermal Systems, and we’ve been highly successful at every installation we’ve attempted.