Lessons Learned From Our First Net Zero Energy Cost Model Home

Posted By on August 4, 2011

$67.53 (Sixty Seven Dollars and fifty three cents).  That’s how much we ended up owing Duke Energy for an entire YEAR’s worth of power on our Net Zero Research & Development model home in Northwind. That translates to just $5.63 per month.

If you’ve been following Potterhill Homes for the past year, then chances are you have heard about this R&D home we built in June of 2010. This home is an 1,800 square foot ranch style home on a full basement.  It has 3 bedrooms, 2 full bathrooms, and ample living space.  We built the home with our signature Potterhill Homes standards including blown cellulose insulation, Low-E EnergyStar Rated Windows, programmable thermostat and compact florescent light bulbs (CFL’s).  Then, we added a geothermal heat pump to heat and cool the home and 3 KW of solar panels to help reduce the energy purchased from Duke Energy.  These two options actually cost less each month when financed on a homeowners’ mortgage than the amount that homeowner will save each month on their utility bill.  These are the only options that actually pay for themselves starting the very first month a homeowner buys them. Granite countertops certainly can’t say that!

When we started construction on this home, our intention was to watch the actual operation of the home’s energy usage for a period of 1 year in order to give us a thorough understanding of what the different seasons did to the homes’ energy use and solar production.

We tracked the amount of money that went out versus the amount of money that came in.  The amount of money that went out was based on how much money we owed Duke Energy each month.  The amount of money that came in was based on the income we earned from the production on our solar panels.  You see, because the home has solar panels, the utility company actually buys Solar Renewable Energy Credits from the system owner, and actually cuts a check to the homeowner for these credits. 

The net result? As of our June Duke Energy statement, the total bill for 1 year of service (which we paid monthly as we went along) was $1280.53.  Then, we subtract the amount of income we received from selling our solar credits.  This amounts to $1227.  The result is a difference of $67.53.  So, our “Net Zero Energy Cost” home actually cost us $67.53 for the entire year’s worth of energy.  Not bad as far as we are concerned!

Our goal this year and beyond is to not only get to a true Net Zero Energy Cost, but to actually earn a small amount of income from this.  We’ll take our lessons learned from this year’s exercise and share them with you here.

First, we learned that geothermal systems almost always need to have air removed from the underground loops a few months after installation.  While there is probably a technical term, we call this “burping” the system.  This process will help the geothermal system operate more efficiently and help save even more money.

Second, we learned that a HERS rating (Home Energy Rating) does not necessarily correspond with energy costs.  In other words, you can manage a HERS score and you can manage energy costs, but lowering your HERS rating does not necessarily mean that you are lowering the cost of energy usage in your home. This is evident in our R& D home.  We installed a gas hot water heater because it lowered our HERS rating, but it actually cost us more to operate than an electric water heater would have because the geothermal unit actually heats the majority of hot water needed in the home, and only operates with electric water heaters.

Third, we learned that having natural gas hooked up to the home costs a minimum of $30 per month even if you don’t use any gas that month.  If we had not had a gas hot water heater and a gas stove, we would have saved $30 per month on our Duke gas bill.  This amount alone would have put us “over the top” and we would have actually come out ahead in our Net Energy Cost for the year.

Fourth, we learned that Duke Energy’s Smart Meters do not work with solar panels.  The Smart Meters will not allow the meter to run backwards- which it often does when solar panels are installed on the home.  We briefly had a Smart Meter installed on our R&D home until we realized this flaw in the technology.  We lost a couple weeks’ worth of solar (income) because of this.

Lastly, we learned not to use the programmable thermostat’s abilities.  With a geothermal unit, it is better to just set the temperature on the thermostat and keep it there.  We found that setting the thermostat on 70 degrees in the winter and on 76 degrees in the summer is very comfortable. Using the programmable thermostat to change the temperature 2-3 degrees when you aren’t home doesn’t make sense with a geothermal unit because it uses more electric to get the temperature back to the comfort zone than it does to just keep the temperature at the comfort zone temperature all of the time.

Even though we are happy with this year’s results, with these fine-tuning tips & tricks, we expect we will actually earn about $220 more than we pay during the second year of the home’s operation.

If you would like to visit our R&D Net Zero Energy Home in Northside, visit our website for directions: http://www.potterhillhomes.com/communities/northwind/northwind.php?id=128

Stay tuned as we post future results.

Potterhill's first ever Net Zero Energy Home in Northside

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About the author

Carolyn Rolfes is the President of Potterhill Homes. And she's also a Rolfes - as in daughter of Dan Rolfes, the infamous Red Tag Man of Holiday Homes. So what does that say about Carolyn and who she is? Plenty. When you grow up the daughter of man who does commercials in his red underwear, you have no choice but to have a great sense of humor and humility from a very young age. Carolyn and Dan founded Potterhill Homes in 2001 and she has grown it to be one of the most successful home builders in Cincinnati. Home building is in her blood and she has a keen awareness of what consumers look for in a new home and how to deliver value at all levels. And while we don't make Carolyn dress up in green underwear for our commercials, we bet she would if we asked!

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About Potterhill Homes

Cincinnati-based Potterhill Homes is a premier builder of affordable, environmentally friendly homes in Greater Cincinnati. Our homes are built with traditional Cincinnati architectural styles and are perfect for both urban infill and suburban development. To learn more about Potterhill Homes,visit www.potterhillhomes.com.


About the authors

Carolyn Rolfes is the President of Potterhill Homes. And she's also a Rolfes - as in daughter of Dan Rolfes, the infamous Red Tag Man of Holiday Homes. So what does that say about Carolyn and who she is? Plenty. When you grow up the daughter of man who does commercials in his red underwear, you have no choice but to have a great sense of humor and humility from a very young age. Carolyn and Dan founded Potterhill Homes in 2001 and she has grown it to be one of the most successful home builders in Cincinnati. Home building is in her blood and she has a keen awareness of what consumers look for in a new home and how to deliver value at all levels. And while we don't make Carolyn dress up in green underwear for our commercials, we bet she would if we asked!