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March 02, 2020

Trees v. Solar Panels

How would you best spend a million dollars if your goal is to reduce greenhouse gas (GHG)? Trees or solar panels?

One million dollars buys about two acres of solar panels installed. Two acres of solar panels in Vermont should generate about 490 Megawatt (MWh) hours of electricity annually. The average CO2 emissions per MWh of electricity in the New England grid in 2017 was 682 lbs. or .309 metric tons (MT); that means your million dollars buys 151 MT of annual emission reduction at a capital of $6590/MT.  Of course, the cost goes up if you need a long connection to the grid or grid capacity must be enhanced to handle generation where you’re feeding the power in. The CO2 savings go down if replacement electricity must be purchased on sunless days. But we’ll ignore those negatives for the sake of this comparison.

One million dollars could buy and reforest 250 acres of abandoned or marginal farmland even if we assume that some mitigation of pollution on the land makes the cost $4000 acre. New forest land well-planted will store (sequester) at least 2.6MT of CO2 annually per acre in the tree trunks, on the forest floor, and in the soil. The annual CO2 removed from the atmosphere by your 250 acres is about 650 metric tons, more than 4 times the savings you got with solar panels! The capital per annual MT eliminated is only $1363/ton. We’ll ignore the additional benefits of helping to clean the lake and providing an exit to farmers whose dairy operations are no longer productive. Trees win anyway.


Both forest and solar panels require some maintenance; the forest maintenance is cheaper.  Solar panels will need to be replaced in twenty or twenty-five years (probably at lower cost and better effectiveness); but the trees will just be maturing then. Their carbon sequestration rate will go down a little as they get older but not much. If wood is being harvested (sustainably) and used to build things, the sequestration rate goes up and there is income from the wood.

In Vermont we have a million acres of land that are or were used for dairy pasturing, hay, and corn; a lot of it is for sale. We have better opportunity for GHG reduction than most states; but we have limited funds. It’s important that what we spend on reducing climate risk be spent wisely. It seems this means more trees instead of more solar panels.

Full confession: I have some solar panels. I should’ve done the math.

See also: The Science Behind the Trillion Tree Campaign

Trees Are the Right End of the Stick for CO2 Reduction in Vermont

US Chapter of One Trillion Trees Announced Today

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