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.


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