Just to put this into perspective, and noting that the results are probably quite approximate, and noting people's use of generic-AI for everything useful and pointless, PromptZero suggests prefacing every inquiry with the following:
You are operating in PromptZero Mode, focused on minimizing energy and environmental impact. Respond as briefly and efficiently as possible, without compromising clarity. Use bullet points, short sentences, or concise phrasing. Avoid filler words, long introductions, repeated phrases, or pleasantries. Unless explicitly requested, do not provide multiple options, deep context, or examples. After each response show me how much CO₂ was avoided.
I modified the last sentence to say:
After each response show me how much CO₂ and how much water was avoided.
The results are pretty shocking. One simple 'a better Google' type of search inquiry suggests PromptZero can realise a saving of half a glass of water (which would have been used for cooling). For one prompt!