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Archive for May, 2011

David and Alice Wagner had a 3.6 kilowatt photovoltaic system installed on their home in Altamonte Springs in 2007 and they have opened it to the public in the ASES/FREA Tour of Solar Homes every year.  When you look at David’s meticulously kept records of reduced electrical usage you can see why they’re so happy.

He set up a three-year base period of kilowatt hours purchased monthly from Progress Energy before the installation and compared that to his kwh purchases every month since the installation.  In the base period he purchased an average of 1,688 kwh monthly.  In the three years including ’08, ’09 and 2010 his monthly purchase averaged 373 kwh, about 78 percent less.  Go Figure!  During March, April and May of this year his Progress Energy bill was $34, $19 and $14 respectively.  The cooling load during the summer boosts up his usage and he says he averages $50 to $55 a month over the year.  Quite a savings from the days when he was paying over $200 a month!

In the beginning days of solar photovoltaic homes it was necessary to include electrical storage for nighttime and cloudy days.  This meant the cost of the system was higher because you had to include batteries.  When it became possible to interconnect a system into the local utility grid it was no longer necessary to buy batteries.  The grid acts as an electrical storage system.  Great savings, but still one significant drawback.  When the grid blacks out, say because of a hurricane, PV systems must shut down, too.  The reason is the electronics in your home could be damaged because the power of the sun fluctuates as it moves across the sky during the day.  Your home requires continuous, uninterrupted power.  Nevertheless, most PV owners today are satisfied to rely on the grid.

The Wagners made the additional investment to protect against grid failure.  By keeping eight, 12-volt batteries continuously charged by the solar system, they can keep the refrigerator, computer and some lights running in the event of an emergency.

It’s already been tested, David says, and it works great.  He was on the computer one evening and walked out into the next room to find most lights out and the grid down.  He said the switch to battery backup was instantaneous and he didn’t even know it had happened.  Another back-up option solar homeowners might try would be a diesel generator.  That would typically cost less than batteries and biodiesel is now available in some Florida locations.

David and Alice have incorporated more than energy savings into their lifestyle.  They have also reduced water consumption.  In the front yard they have cut back on the amount of grass that might need irrigation and they are planting a native plant/butterfly garden.  Once these plants become established they’ll survive on rainwater.

David says in the back of his mind he sees an expanded PV system and an electric car in the garage.  Stop by and let him tell you about that during the next Tour of Solar Homes.

Sam Kendall

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