Northwood News ♦ February 2016

Installing a Geothermal Heat Pump in Our Back Yard

By Bob Loube

Installing a geothermal heat pump is an adventure.  We had a system put in last July, when our air conditioner died.

First, the tomatoes, corn, and topsoil in our backyard vegetable garden were removed so workers could use enormous drilling equipment to dig a 341-foot well about a foot in diameter.  When the drill bit hit the water table, brown water gushed out of the well like a small geyser.

Next, they dug a trench from the well to the back of our house.  Pipes were inserted in the well and the trench.  The pipes carry the fluid that helps the heat pump heat and cool our house.

In the summer, the geothermal heat pump transfers heat from the house to the 50-degree earth.  A standard air conditioner transfers heat from a house to the 90-or-so-degree air outside.  Because it is easier to transfer heat to 50-degree earth than to 90-degree air, the geothermal heat pump should cut our air conditioning electricity needs in half.  As an additional benefit, the geothermal heat pump has no outside unit, so our backyard is now quiet in the summer.

In the winter, the geothermal heat pump extracts heat from the 50-degree earth to heat our house.  A standard heat pump must extract heat from the 30-or-so-degree winter air to heat a house.  Due to the difference in the temperatures of the two heat sources (earth vs. air), the geothermal heat pump should reduce the winter heating bill for a home currently using a standard heat pump.  In our case, because we previously heated with natural gas, our winter electricity bill has increased, but our winter gas bill now looks like our low summer gas bill.

To achieve these savings, it was necessary to spend additional dollars today to purchase and install the geothermal system.  The cost of the geothermal system was greater than the cost of simply replacing our air conditioner would have been.  Part of that additional cost was offset by rebates from Pepco and the State of Maryland, plus a federal tax credit.

Given the low price of natural gas, I have estimated that there will be an eight- to 10-year payback period associated with our purchase.  For someone already heating with a standard heat pump, the payback period should decrease to five years.

To summarize, the benefits of a geothermal heat pump include reduced utility bills, reduced usage of fossil fuels, and a quiet backyard.  The costs include the additional initial cost of the system, the loss of one year’s vegetable crop (we’ve been able to replace the vegetable garden over the site of the well), and the need to reseed the grass where the trench was dug.

[Bob and Robin Loube live on Cavalier Drive.]   ■