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Friday, September 23, 2011

48% of Our Electricity Comes From Solar


In November of 2010 our 3.4 KW Photovoltaic solar system installation was completed by SolarCity. The question since we started this project was how much of a home's power can you generate with solar power here at 45 degrees North latitude? I've heard people claim 50%.

We are well over 8 months into 2011 and through the month of August our PV solar installation has supplied 48% of our electricity. The chart above, which is a chart supplied by SolarCity automatically shows how much was generated by the solar panels each month and what percentage of our average monthly usage that is.

Monday, February 28, 2011

How Much Of Your Home's Electricity Can Solar Generate?

The chart above shows how much electricity our solar panels generated during the month of February 2011. The vertical green bars show how many kWh (Kilowatt hours) our panels create each day. The red horizontal line is at 21 kWh. 21 kWh is the average amount of electricity that we use each day based on our consumption the last two years (2009 & 2010). 21 kWhrs is also the design target for our solar installation. That is, the most our solar system will generate is right around 21 kWh's. If we are not home and don't use all the power the solar array is generating the unused electricity goes out on the grid and PGE sells it to our neighbors. If we use more than the solar array is generating we use electricity from the the grid.

As you can see about 9 days during February the panels generated over half of our electricity. On 2/25 the panels generated roughly all the electricity we used. As we move towards June 21 when the Sun is the highest angle we'll have more and more days like 2/25 Over the whole month the solar panels generated roughly 44% of our electricity.

The reason there is so much variability from day to day in power output is due to the variation in cloud cover. The other factor that influences power output is how high the Sun is above the Southern horizon. In the summer months there will be more and more days where our solar array will generate all of our power (21 kWhrs)  each day.


Wednesday, February 23, 2011

Well Insulated and Sealed Homes Don't Need a Furnace!


Heat your home by throwing a dinner party?

This concept may sound bizarre, but it's feasible in cutting-edge green homes that are so well-insulated, they don't need a furnace or boiler. They'll stay warm simply with body heat. A hairdryer might also suffice.

"It's like living in a glass thermos," says John Eckfeldt, a physician who built one of these "passive" homes in frigid Isabella, Minn. He says the inside temperature is so even that if he sees snow falling, he's surprised to realize it must be cold outside.

 Click here to read the complete USA Today Article.