Last week, we threw the switch to our geothermal HVAC system that is correctly called a ground source heat pump. When we bought this house, we knew the almost 20 year old, inefficient HVAC propane heat pump had to be replaced before winter. As we made plans for this conversion, we learned that we had one factor in our favor. Joe, the original owner/builder had two wells put in and both were plumbed underneath the house. Joe wanted to make sure he had water. One of the major deterrents to the geothermal system is drilling and putting in the wells. Luckily, we did not have this cost, and the backup well pumps at 80 gallons a minute, and the geothermal process takes 3 gallons per minute which helped our conversion in this project. The only additional cost incurred was running a 2-inch PVC drain line to our pond.
The story only gets better. First, all ground source heat pumps are about 60% more efficient than high efficiency heat pumps. Second, we will program the system to run based on the “time of use” rate so most of the time it will run at .049 kW, not the normal .12 kW rate.
The next big benefit is free hot water. Remember, we kept our electric hot water tank and installed a timer. The ground source heat pump when running will discharge 150F water. That hot water tank will be used as a storage tank, and it will only come on in the early AM as a backup, if the heat pump does not come on. Husbands take note; it is not a good marriage plan to have the wife take a cold shower.
The final icing on the cake is related to the tax breaks: 30% federal tax credit for the total investment and 35% North Carolina personal tax credit. Roll it all up; I estimate this will have a payback of less than two years!
Since moving into the house, I have used our Plotwatt data to determine that our hot water and HVAC use accounts for almost 40% of our electric bill. So, I am optimistically expecting a big drop in our electric bill and that is why I see our HERS rating improved from 90 to 61.
Stay tuned, we are over half way to the net zero home!