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In the solar industry, we often get trapped in focusing on the investment side of the solar justification while forgetting the energy independence and environmental side.  So I think it is time to take a look at what is the mix of resources being used every time we use a kilowatt of electrical energy. Also, and more importantly, how many pounds of CO2 (green house gases – GHG) are released with each kWh of our electrical usage.  My primary sources come from the US Energy Information Administration, a recent seminar on Impact Sonoma, and my personal experience.  PG&E is one of the cleanest utilities in the nation burning only .65% coal.  The renewable energy figure includes large-scale Hydro (dams), which is not included in most measures as a renewable resource.  And while hard to find, almost 50% of all PG&Es power comes from the burning of Natural Gas.

The primary renewable energy in PG&E’s portfolio mix is our local gem, the Geysers geo-thermal plants.

Calpine Geo-thermal Power Plant

Calpine has the lions share of the plants in this area, producing 725 mw of renewable energy.  This represents 21% of all California renewables and 41% of the geo-thermal energy in the US.  PG&E  considers nuclear energy as part of their renewable energy portfolio, yet this is not a standard interpretation.   While nuclear can produce reliable energy it has a limited life and can cause environmental damage.  Look at the San Onofre power plant that has been off-line since 1/31/12, due to leaks in radiation and excessive tube wear.  Southern California had to scramble to make up this loss to their grid, including firing up two dirty plants to meet the demand.

  So back to the original question, "how much GHG is released when we use a kWh of energy from PG&E"? To answer this question, we need to look at the detailed mix of PG&E’s energy portfolio.  While PG&E burns very little coal (under 1% of the total), the fossil fuel mix is made up of 49% natural gas, 22% nuclear, 18% large Hydro,  and 19% renewable.

While CO2 is naturally released in nature, fossil fuel plants burn a resource that took millions of years to produce, and the process of burning it releases large quantities of CO2 into our atmosphere.

A fossil fuel generation facility

These large releases cannot be absorbed by our plant population which converts CO2 to oxygen naturally.  The excess CO2 is the leading cause of GHG (green house gases), which causes global warming.  This has led to many programs that include planting trees, moving towards high mileage and electric vehicles, and the increasing demand for renewable energies.

Utility scale solar systems are on the rise
 
So if you do not have solar, when you use a kWh from PG&E, some where, fossil fuels are being burned.  One kWh of electrical energy from PG&E releases .77 pounds of CO2 into the atmosphere.  For a typical Sonoma County home that uses 500 kWh per month and this equates to over 2.5 tons of CO2 release every year.  One benefit of renewable energy’s, and solar in particular, is that solar energy creates no CO2.  The sun, while it is burning up, still should provide us with 1 billion years of usable energy.  Another interesting tidbit, the energy it takes to produce a complete solar installation, is made up in the first 1-3 years depending on the system installed – and this will be covered in more detail in my next blog.