28 Sep 2026
Carbon awareness vs. energy efficiency
When people talk about greener software, they usually mean making it more efficient: fewer servers, lighter pages, fewer tokens. That matters, but it's only one of two levers.
Efficiency reduces how much energy the software uses. Carbon awareness is about which energy it uses. The same kilowatt-hour can come mostly from wind or mostly from gas, depending on the time of day and the region.
A 2011 study on the Irish grid made this very concrete for me. The authors calculated the CO₂ of a single computing job and showed that running it at a different time would cut its emissions by about 45%, without changing a line of code.
I thought about this recently with a client project. We have an AI forecasting job that runs every two weeks, and I scheduled it at an off-peak hour because one provider charges half price then. Good for the budget. But when I reviewed it later, I realized I had chosen that hour for the price, not for the grid. The cheapest hour and the cleanest hour are not always the same.
So now I ask two questions about any workload. Can it use less? And can it wait, or run somewhere else? A live online store can mostly answer only the first one. A scheduled job like that forecast can answer both.
Originally posted on LinkedIn ↗