Finally (!) we get around to answering the questions on the banner of this site. Those questions are:
Solar Panels alone? Or Solar Panels plus a Home Battery? Or even a Home Battery alone? Which would lower your carbon footprint the most?
Now that we've covered all the other stuff, we're ready for an answer. And the answer is... it depends on where you live. This post will be the first in a series that lays out where (and when) each option reduces one's carbon footprint most effectively.
If you've read through all the previous posts, you know we've come to a few basic conclusions (again I don't pretend that these numbers are all exactly right, but everything I've learned over the past year tells me that they should be "in the ballpark"):
- In a 100% Coal grid, adding Solar above 11 - 15% leads to cycling, and that the cycling of Coal plants can emit as much CO2 as was saved by the Solar.
- In a 100% Nat Gas grid, adding Solar above 15 - 18% leads to cycling, and that the cycling of Nat Gas plants can emit half as much CO2 as was saved by the Solar.
- In a grid that is 50% Coal / 25% Nat Gas / 15% Nuclear (similar to Ohio), adding Solar above 10 - 13% leads to cycling which can emit nearly as much CO2 as was saved by the Solar.
- No grid can handle above 25% Solar if there is no storage (like batteries).
If you take the four bullets above to be true (and I think they are), then you can clearly start to see what to do with your own home in order to lower your carbon footprint as best you can, and it goes something like this:
- If you live a state that generates less than 10% of its electricity from Solar, then probably Solar Panels alone are best. Note that as of 2016, this includes nearly every state in the US.
- If you live in a state that generates between 10 and 18% of its electricity from Solar, then probably Solar Panels plus a Home Battery is best.
- If you live in a state that generates over 18% of its electricity from Solar, then there is too much Solar for the grid to realistically handle already, and a Home Battery alone would be best.
A few comments on the conclusions above. First - if you haven't read the previous posts I encourage you to do so, as I take you step by step through how I reached these conclusions. Secondly, these conclusions apply to the US electrical grid as it exists now - most notably that there is no significant energy storage and no long distance transmission lines connecting the coasts. Thirdly, one has to consider not only how a state generates electricity right now, but also how that state will generate its electricity in the near future. After all, if your state is at 8% Solar, then it will likely be above 10% soon. Fourthly, I'm not taking money into account (a big one, obviously). Finally, if you read about the system in our house you might think putting a Solar + Home Battery system into a home in Ohio was foolish (and you might be right), but I'll get to my reasons for "jumping the gun" on home batteries in a future post.
You also might be thinking... do any of these conditions in 1-3 really exist somewhere in the US? That will be the subject of the next three posts, and if you're skeptical about condition 3, then I encourage you to search the internet regarding the Solar electricity situation in Hawaii.