Sunday, November 19, 2006

How Much Oil Did the Solar Panels Save?

How much oil did the new solar panels save? Short answer is not very much.

To get an estimate, I went to the website of the Energy Information Administration (EIA) which is part of the Department of Energy (DOE). If ever there is a government agency that is worth their salt, it is the EIA. (I'd also put NOAA into that category, but that is a topic for another blog). If one has any interest whatsoever in understanding energy issues in the USA and the world, then a visit to the EIA website ( is a necessary stop. I wouldn't put a lot of trust in their forecasts, but their compilation of historical data is outstanding.

In their section on electricity, one can find the generation data for all states and for the USA as a whole.

The first pie chart shows the generation portfolio for Connecticut. The primary fuel source is nuclear followed by natural gas, cola, renewable, oil, hydro, and lastly other types. For the USA, the generation mix is a little different as seen in the second pie chart. Compared to the rest of the nation, CT uses substantially more nuclear power and substantially less coal.

The striking feature of both charts is how little oil is used (listed at Petro in the bar graphs). Nationally, only 3% of the electricity is generated using petroleum or products. In CT, the fraction is 5%. These values were obtained from the October Monthly data and are the actual fuel mix for the year 2004. One has to go back to before the oil crises in the 1970s to get a higher fraction of oil use in electricity generation.

So how much oil was supplanted? It is tempting to just say that only 5% of the solar power generated by our tiny array was used to supplant the oil, but that isn't exactly correct. The thing that is missed is that with respect to power generation, the different fuel types are used at different times of the day and in different seasons. Power usage peaks in the late afternoon and in the summer.

Generally, the cheapest power to make is generated first, followed by the next cheapest, etc. The base power is nuclear, and this gets generated whenever the power plants are not down for maintenance. Next come hydro (if available) and coal followed by natural gas. Petroleum is usually the last one to be called, and it doesn't happen too often unless the petro plant is a "must run" station that is needed for the stability of the power grid.

The power supplanted, then, is the fuel with the marginal cost at the time that it is generated. Most of the time when the solar power is being generated (mainly summer months and midday), this will be natural gas, but it could also be the other components. I haven't calculated the exact amount, for that would have to be done with hourly data. These hourly data are possible to get, but it would take a bit of time and effort to work out. I may try it in the future, but I haven't done it as yet. But it is safe to say that hardly any coal and nuclear have been eliminated by the solar panels, the bulk of the solar power is substituting for natural gas, and some of the petro is also being substituted out.

The bottom line is that the solar array hasn't as yet made an appreciable dent in my oil consumption, but it has reduced the natural gas usage. This is important if one is concerned about greenhouse gases (and it isn't clear at the moment that I am), but it isn't optimal if that is your primary concern either, for more greenhouse gases are generated by coal and oil than by natural gas.

To eliminate the coal by solar, one has to generate enough for the day usage and also generate and store enough of the solar (or wind) power to last you through the night time as well. It is difficult to see how one could eliminate coal entirely, unless the entire roof of the house was covered with solar panels (not practical today but potentially possible someday), and a large battery or other backup system (which I presently do not have) is installed.

So why did I put in the solar panels then? That is a very good question.

The first answer is that if I had thought about the generation data beforehand, I may not have done the array first. If someone is on a limited budget and looking for methods to reduce dependence on foreign oil or reduce greenhouse gases, the money is best put towards better gas mileage or other forms of heating the home if fuel oil is used. Eventually though, I would have gotten around to it.

The second answer is that natural gas has its own problems (notice the price of natural gas lately?), and I'm trying to stay away from natural gas as well. Further, the use of the sun for power generation fits into the vision of how I think things will go if the peak oil and the peak natural gas people are even half right. That needs elaboration (in a future post).

There is also the fact that any net reduction in natural gas, especially permanent ones like solar panels, will probably end up reducing the use of oil, because the markets tend to used the cheaper sources, and presently that is usually natural gas, so if users of solar power are no longer using as much natural gas for power generation, the price will be lower, making it an even better alternative to oil and products, insuring more natural gas gets used in other areas such as petroleum refining, etc. This substitution, though very real, is a second level effect.

Finally, the primary reason is that it made sense from a financial (as well as a power) risk management perspective. The financial aspect is the subject of the next post.


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12:09 AM, December 15, 2015  

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