Solar vs. “The Grid”

Solar vs. “The Grid”

How can we know where—and by how much—power from solar photovoltaics (PV) is better than grid electricity? What does this mean for solar subsidies?

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Solar Electricity Lifecycle

Wednesday, June 4, 2014 - 11:15am

CAMPAIGN: Source Energy Blog


One Method for Any Energy Source

Our approach to assessing source energy efficiency is the same for both solar power and grid electricity. And while our analysis is based on large datasets, the results are actually pretty easy to understand.

To do this, we have developed a system that takes time, location, and “site” consumption as inputs, and then provides “source” (life-cycle fossil fuel) consumption as an output. For example, an input may be the kilowatt-hours (kWh) of electricity in a specific location. The output would be the amount of fossil fuel used to generate this electricity, including indirect energy consumption for mining, shipping, etc. We measure it in a unit called an Energy Point, or EP, which is equivalent to the source energy of a gallon of gas. 1 EP equals 144,000 BTU of fossil fuel. One gallon of gasoline typically contains about 114,000 BTU of chemical energy, but sourcing it requires an extra 30,000 BTU, on average. That’s why we’ve chosen our unit to be 144,000 BTU (1.08 gallons) of crude oil or “source energy.”

Solar Efficiency

For comparing solar power to grid power, we’re interested in the kWh out per unit of fossil fuel in.For solar, the source energy efficiency of the photovoltaic system depends on a number of variables. The first is a matter of where and how the panels are manufactured, because of variations in the on-site operational efficiency of the....

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