2014 Habitat for Humanity Builders Blitz Is Underway
June 5, 2014
Moving into the Evergreen: Green Living
March 19, 2011
Two Homes, One Week
June 19, 2014
Getting to Net-Zero Energy
October 7, 2013
Our new home is very energy efficient, but some people have asked why we weren’t able to achieve Net-Zero Energy use for the home. The simple answer is that it would have cost a lot more money up-front and would involve the installation of photovoltaic panels.
As I mentioned in my previous article, our first energy priority was to reduce electricity consumption through efficiency. We spent time early in the design process to model the energy performance of the home with different windows, insulation, and other products to help us make smart selections. After finishing the renovations, we tested the performance of the home and received a score of 56 on the Home Energy Rating System (HERS). This means our home is 44% more efficient that a standard new home of the same size. The HERS index also provided an estimate of $2,736 for the annual energy costs for the home (approximately $228/month).
A net-zero energy house would have a score of 0 or less on the HERS index, so what could we have done to reduce consumption further? There isn’t a simple answer in our case because interior design and lifestyle decisions had an effect on the overall efficiency of the home. For example, we chose to build a pool in the back yard and pool pumps for pools are traditionally energy hogs. We opted for a variable speed pump to minimize energy use for the pool, but still use more power than if we didn’t have a pool altogether. There were also certain upgrades that we could have chosen in the mechanical systems, but didn’t view them as worthy investments. There are also many other choices on smaller systems that affect overall energy use.
After maximizing efficiency, the simplest way to get to net zero energy is to offset our consumption with the production of power. In our area, photovoltaics (PV or solar arrays) are the most common residential electric production method, so we just have to figure out how large of a system to install. Based upon our HERS index, we should average about 2,000 kWh each month (this is very close to our actual consumption during the first six months of living here). A 16kW PV array would be required to produce this much power and would cost approximately $64,000 before tax credits or utility incentives. There is a federal tax credit of 30% and also some electric utilities offer incentives, but without either of those - the cost is very daunting.
It is generally less expensive to maximize efficiency of a home than it is to offset consumption with power production. In the end, if you truly want a net zero energy home and maintain many of our everyday comforts, you will likely need to install PV panels. We strove to maximize our efficiency, but may consider adding PV to offset our consumption if we qualify for our utility incentive. That may lead to an interesting upcoming article! Always remember to ask your licensed contractor about green building and how they can incorporate any of the ideas I’ve shared into your project.