Does reserving digital solar work the same way as rooftop solar to cut down on my carbon impact?
Somebody recently asked: Using digital solar we aren’t utilising green energy but just offsetting our power bills, so is it really ‘green’?
TL;DR: Yep, what matters is greening our grids’ power mix, which among other ways, is enabled by digital solar.
Now for the slightly long version;
Electricity, like money, is fungible. What that means is 1 kWh (unit) of electricity functions like any other 1 unit of electricity regardless of where it came from. Just like how one ₹10 rupee note has the same value as ten ₹1 coins, irrespective of the fact that their weight, materials used and shapes are all very different.
While electric current remains agnostic, what differs is the energy sources we use to make the electric potential to drive this current. And today it comes from a combination of thermal (coal and oil), hydro, solar and others. The below chart shows what is our ‘power mix’ or what contributes to making of our electric power.
So when we pull power from the grid, a large chunk of that comes from fossil fuels and with getting ‘green energy’, this isn’t really to look at our residence or workplace as an isolated system, but rather what is our contribution in terms of demand from the grid and where the grid is generating supply to meet that demand.
One elegant analogy I have come across that explains this well is from a paper Google wrote when they were exploring off-site solar for themselves:
“Injecting clean power elsewhere on the grid is just as good as consuming the renewable energy directly. That's because electricity on a grid is fungible; electrons generated in one spot can't be directed to any specific user on the grid, any more than a cup of water poured into a river could be directed to a particular stream. So it doesn't make much of a difference where the renewable energy is delivered, as long as it's on the same grid.”
https://sustainability.google/progress/projects/ppa/
Is that the same case for rooftop solar?
Well yes! Most home rooftop systems are grid-tied or grid interactive. What that means is power is injected into the grid (either through net-metering or gross-metering) which enables us to offload surplus power generated, as well as pull power from the grid on a cloudy day or at night, turning the grid into a giant battery of sorts.
Therefore grid power mix is what matters and going solar anywhere the grid is present enables us to participate and do our bit in greening it.
Quick side note; In India, we have five big grid segments (Northern, Western, Eastern, Southern and North-Eastern) out of which multiple power generators and distribution companies (like BESCOM, Tata Power, MSEDCL etc) operate out of. But since all of them are interconnected and supply and demand on one affects the other, when we say ‘the grid’, we mean the national electric grid as a whole.