Equinox House is just about to complete its first fully, solar powered lap around the sun (February 23, 2010 is the solar energy system’s “birthday”).
At a recent holiday party (this is being written in early January, 2011), a neighbor came up and asked what our utility bill was for December (the bills had just arrived). His bill was over $500, and he was quite surprised when he learned that the energy bill for Equinox House was zero….as it has been every month since we switched the solar PV system on last February. December 2010 was the third coldest on record for central Illinois, and was our snowiest December ever with 20 inches of snow (yes, we realize that to our friends in the UP, this is nothing by your standards). This solar stuff really works! But the big question is whether it is worth it or not, so let’s do the numbers.
Overall, our 8.2kW grid-tied, solar photovoltaic (PV) system is designed to produce 10,000kWh of electricity per year. The installed cost of our solar PV system was $35,000. This includes solar panels, wire, postholes, support steel, conduit, concrete, inverters, disconnects, shipping, and labor. The federal tax credit is 30%, so this is a direct rebate from our tax bill of $10,500. This is not a gift from the government. This is a small portion of your tax money that you finally have a say in where it is spent. So, the net cost of the solar system is $24,500. Of this amount, 80% ($19,600) is for the solar system that provides 100% of Equinox House energy needs over the course of the year. The remaining 20% ($4900) of solar system cost is for powering an electric vehicle 6000 to 8000 miles per year at an equivalent gasoline cost that is less than $2 per gallon (see the section on transportation for more details).
So, we have spent $20,000 for a solar energy collection system that provides all the house annual energy needs. Is it worth it? We won’t complicate things with discount rates, escalation factors, opportunity costs, etc, but will keep things simple. The solar panels are warranted for 20 years. So, we’ll figure they will only last 20 years. The infrastructure (~25% of the overall cost) should last longer, and the inverters probably last less than 20 years (warranted for 10 years), but again, without complicating things, we’ll say that the solar system for the house cost $20,000 and lasts 20 years, for an average “electric” cost of $1000 per year.
One way to think about the solar system is that you paid 20 years worth of utility bills up front, and that your monthly energy costs $83 per month ($20,000 divided by 20 years divided by 12 months per year). Not bad! There are many ways to view this investment, and you should decide on the best way to view it for your situation. Regardless of how you think of it on an economic basis, a solar powered house is affordable, it moves your money into your local economy and into the manufacturing sector, which leads to healthy, happy communities.
This brings up the other side of the issue. How do you build a house that only requires $83 per month in energy cost in our challenging climate with lots of cooling, dehumidification and heating requirements? Read our features that cover the costs and performance of Equinox House to learn about places where we spent extra money (insulation and caulk) and where we saved money (no ceiling fans needed or wanted because the house naturally maintains a uniform floor-to-ceiling temperature; no roof vents needed or wanted; no clothes dryer vent needed or wanted; no natural gas needed or wanted along with associated costs of gas fixture installations, generation of indoor air pollutants, flue vent installation costs, and no monthly natural gas customer service fee from the utility that can add up to more than $5000 over 20 years.) And best of all, Equinox House requires no sacrifices…all the expected creature comforts including a custom Italian gourmet kitchen with the highest quality appliances and tiled bathrooms….sustainability and luxury are not mutually exclusive!
December 2010 utility bill showing zero energy cost
Slide from Equinox presentation in Turkey with estimated cost differences between Equinox and conventional residence
Slide from Equinox presentation in Turkey with estimated monthly payment difference between Equinox and conventional residence
