Should I cut down a tree shading my roof to make way for solar panels?
Posted by Jason Ramsdale on 10 December 2015 at 2:15 pm
Solar panels and trees aren’t always the best of companions. Branches and leaves may cast shade over your panels reducing their efficiency.
This is an interesting moral dilemma. On one hand you have the benefits of reducing your carbon footprint by switching to solar power. On the other hand cutting down a tree doesn’t seem like the most environmentally friendly thing to do.
Trimming a few branches may enable you to clear enough space to allow your panels to generate unhindered. However, would sacrificing a tree be for the greater good? To try to solve our moral dilemma, we could ask how much carbon does a tree store and how does this compare to the CO2 savings from solar?
How much carbon does a tree store?
To work out whether it’s worth removing the tree and installing solar panels from a carbon saving perspective requires some maths. In a separate blog, we went through the maths to calculate how much carbon is removed from the atmosphere by a tree, using Ecometrica's example of a 12 metre high sycamore. This is a particularly big tree, about double the height of a normal house! The example tree had taken 3.6 tonnes of CO2 from the atmosphere.
This sounds like a lot! But, to put it into perspective we need to work out how much CO2 will be saved from having solar PV panels instead of taking electricity from the grid.
How does this compare to the CO2 savings from solar?
The amount of CO2 released per kWh is not constant but varies on an hourly, daily and yearly basis. However, we can use 0.4 kg/kWh as a rough estimate for the UK National Grid.
In the UK a 4kWp PV system will typically generate 3,400 kWh per year. Over a 25 year lifetime this equates to 85,000 kWh or 34 tonnes of CO2 saved.
If we subtract the CO2 costs of cutting down the tree (3.6 tonnes) and of installing a 4 kWp system (2.5 tonnes of CO2) we get a saving of around 28 tonnes of CO2.
From a carbon perspective, removing a standard tree to give you the freedom to install solar panels looks to make sense. You'd have to grow around 8 large sycamore trees to maturity to achieve a carbon reduction equivalent to that of a 4kWp PV system. If the PV system lasts longer than 25 years even more CO2 would be saved.
But, our maths have only really considering the impact on the environment with respect to CO2 emissions, and there are other things to take into account. Aside from looking pleasant, trees can provide valuable habitats for animals including birds and bats. Simply replanting a new tree might not serve as an acceptable habitat replacement as it can take a long time for a tree to mature and develop nooks and crannies needed for some animals to roost. Before making a decision to chop down a particularly old tree, like a 200 year old oak, it might be best to consult with a local ecologist to assess what the impacts might be, and how best to mitigate them. In some areas you may need to consult your local council before pruning or felling trees.
 The Eco Experts
 GMI Energy Expert states a panel generating 211 kWh per year creates 0.03 kg per kWh of CO2. A 4 kWp produces 3400 kWh per year. Meaning approximately 16 panels are needed. So a total of 85,000 kWh over a 25 year life time. This equates to around 2.5 tonnes of CO2.
Photo: Sonja Pieper
More information about Solar Electricity on YouGen.
Need help with any Jargon?
If you have a question about anything in the above blog, please ask it in the comments section below.
3 comments - read them below or add one