Question: How can I be certain that the geothermal system in my new home is set to run in the most efficient, cost effective mode? Also, is there an online tool or chart that will help me determine if my electricity consumption is above normal for my size home using a geo unit? It sure seems like my first month’s electric bill was quite high... higher than I guess I was expecting. – Cory, a Smart Choices reader
Mr. Tight-Watt called on Rick Rockacy, Iowa representative for WaterFurnace International, a geothermal manufacturer, to weigh in on Cory’s questions.
Answer: Cory, first, congratulations on selecting the most energy efficient heating and cooling system available! You have made a wise investment.
A new home can be a bit of a challenge to determine “typical” utility costs. It is important to bear in mind that the geothermal system uses electricity to operate compressors, fans and pumps in the operation of the system. Thus the electrical usage may be greater compared to a conventional (gas, propane) system due to longer run times of the geothermal system. However, to compare true costs of heating and cooling your home, you must also add the additional fossil fuel costs to estimated electrical costs, which should make your geothermal unit “shine” in comparison!
Many geothermal systems today are designed to operate in the most efficient and cost effective mode. This is controlled by the microprocessor board in the unit. It is also impacted by the type of compressor, fan and other components that were specified for your home by the dealer. Geothermal systems are designed to operate properly without a great deal of attention by the homeowner … other than the items noted below:
1. It is important that the contractor properly size the geothermal system. That means that the dealer should perform what is known in the HVAC industry as a Manual J Heating and Cooling load calculation before bidding on your project. This is a calculation that determines the amount of heat (expressed in BTUs) your new home gains and loses throughout the year. Due to the precise nature of geothermal systems, proper sizing is critical to the optimum performance of your new geothermal system.
2. The contractor should also size the “loops” in the ground to the load of the new home. In many cases, the contractor will size the loops to the heating load of the home although they can choose to size it to the cooling load as well. One loop can handle 12,000 BTUs of load on your home; the number of loops will be based on the Manual J calculations.
Assuming these two steps were taken, you are well on your way to ensuring your system is set to run most efficiently and cost effectively.
If you are concerned about your electric usage, there are several more steps to consider:
1. Consult with the installer to be sure that all components are functioning properly. Your installing dealer is a good source of guidance and expertise, and should be the first one you contact.
2. If you are an REC member and your geothermal heat pump is separately metered, check with your REC to provide you with a record of geothermal usage separate from other electrical items in your new home. Computers, appliances, TVs and more all draw on electricity; this is to make sure you are looking at what the geo unit is actually consuming.
Cory requested information about ways to calculate what his electrical usage should be with a geothermal unit. Here are several that may help him, and you, too, if you are considering a geo installation for your home.
1. Your electric cooperative subscribes to a calculator that may help you find out more about your home’s energy use. Check out Home Energy Suite and click on the Calculators button.
2. Rick also suggests using the WaterFurnace calculator. He notes that it is primarily designed to help determine what the payback might be in your existing home. In Cory’s case of a new home, Rick suggests, “if the Savings Calculator doesn’t pull the accurate info (due to the home being brand new), put in the home’s square footage and type of “conventional” system he would want to “compare to.”
Maximizing geo efficiency
Over the long term, another key to ensure that your system is running effectively is to keep the temperature set to a level that you are comfortable with, and not changing it from that set point. It is important that once you set the temperature, you don’t want to change it daily, weekly or even monthly. Geothermal systems have a much longer “run time” than conventional systems. This long run time ensures the system is working at its optimum.
Here are a few other things that can be done to insure the equipment is running in the most efficient mode:
• Keep the filter clean – change per the manufacturer’s recommendations
• Check the drain pan – ensure drain hole is not plugged
• Check ductwork – ensure registers are open and ductwork connected
• Check the thermostat – check for fault signals or if emergency heat has come on
• Check the unit – for moisture around units or flow center
Rick Rockacy, Territory Manager
Ask Mr. Tight-Watt a question about lighting or other topics relating to energy use and efficiency and find answers to other questions Mr. Tight-Watt has provided.