Commentary: Does a net-zero energy home live up to expectations?

By Van Gooch, member of Citizens for a Sustainable Future, Alexandria, MN

After 12 years living in our net-zero energy home, featured twice on the front page of this newspaper (October 6, 2015 and July 7, 2011), I thought an update of its energy performance would be of interest. The data show that our 7.6 KW solar panel system has provided ALL of the kWh used by our all-electric home. When the sun shines, we are generally making more energy than we need, so we sell the extra to Runestone Electric Association in a program called “Net Metering.” When the sun is not shining, we buy back the needed energy largely at “off-peak” rates. Over a year, the energy produced by our solar panels covers our needs for heating, cooling, hot water, appliances, etc. The solar panels pay for almost all of our electricity, while we still pay a monthly service charge to be connected to the grid.

We built the house with energy efficiency in mind. Extra insulation beyond code is in the ceiling, in our one-foot-thick walls and under our cement slab. Heating, which uses 43% of our annual energy, is achieved by using a highly efficient ground source heat pump. In the summer the heat pump can be reversed for cooling, which accounts for only 2% of our total yearly energy. When the sun shines in the winter, the triple pane windows that are facing south are very effective at providing a source of heat (known as passive solar heating). In the summer, the sun is at a higher angle such that our four-foot eaves block the direct entry of sunlight through these windows.

In examination of monthly data, our solar panels have shown zero depreciation of effectiveness over the past 12 years. In the summer we produce on the average 923 kWh per month and in the winter the production is 626 kWh per month; this drop from summer to winter may not seem as large as one might expect. Two factors help energy production in the winter: a), I tilt the panels so that they better face the winter sun and b) electricity flows more efficiently in solar panels as the temperature drops.

So, does our net-zero energy home live up to our expectations? The answer is a resounding YES.

We built this home as a model to demonstrate what can be done in our challenging northern climate and I encourage anyone to contact me for more in-depth information. This is a great time to consider using more sustainable energy sources. The Inflation Reduction Act recently passed by the federal government, offers many opportunities to lower the use of climate-warming fossil fuels. The IRA is designed to most help the median and low-income earner. A good place to learn about the IRA as it applies to Minnesota is the CERT’s website ( www.cleanenergyresourceteams.org ).