Where Are We On The Road To Net Zero?
Today's date is September 15, 2011 and I can tell you what really happened.
We are not quite Net Zero.
Our first full year in the house produced a net energy use of 2,000 KWh's and the second year required 1500 more KWhs than we produced. Not bad for a 2,130 square foot house, but not Net Zero. Our 3.3 KW solar PV array is just a little small. Some day we will install another 1.5 to 2.0 KW of additional PV and that will do it.
Until then I will explore what sort of cost-effective measures we can undertake to further reduce our energy demand. And from now on, I plan on being more diligent in updating this web site, too.
Toward a True Net Zero Energy Home
(December 2009)
Our "Smart Meter" was installed on February 5, 2009 and our 3.3 KW PV Solar Array was activated on the same day. Our Solar Thermal Domestic Hot Water system and our insulating Levolor "honeycomb" window shades had been installed in our all-electric home in December of 2008, so we were fully functional and ready to kick some carbon!
With all systems functioning, the smart meter slowly accumulated KWh's on the consumed (positive) side of the meter until April 20 when we reached the level of 347 KWh's consumed. Warmer weather and longer days started a steady decline on the positive side of the meter until June 13, when we hit zero!
We are now into the negative side of the meter and it sure looks strange to see a reading like 99979 ! (For comparison, Xcel's average residential customer in Colorado uses 632 KWh's of electricity and 69 Therms of natural gas per month! That is equivalent to approximately 30,000 KWh's per year for the mythical "Average House". We expect to use and generate just under 5,000 KWh's per year resulting in a true Net Zero Site Energy house!)
Progress Report
We continued to generate excess electricity throughout the summer and early fall until October 8, when we hit our low point of 99156 on our Smart Meter. Cold weather and snow (covering our flush-mounted PV panels) have put us in the conventional situation of actually using power from the grid on a monthly basis and we are creeping up from negative use to Net Zero energy use.
We have had a bout of real winter weather here in early December, with days of no sun at all and temperatures no higher than the low teens! Heating the house has resulted in total electrical usage in the 60 to 80 KWh's per day for several days in a row.
My best guess, today, (December 12), is that we will end up seven to eight hundred KWh's on the net consumed side of the Smart Meter on December 31. Of course, we did not get the Smart Meter installed until February 5, 2009, so the true first full year net energy use figure will not be known until February 5, 2010.
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