How to Use the Right AI Model for Greener Use
Most of us open ChatGPT, Gemini, Claude or Copilot and use whatever setting comes up. More and more often, that means a large model that “thinks” before it answers. Using that to tidy an email is like hiring a removals van to post a letter.
Choosing a smaller, faster setting is one of the simplest Green AI habits there is. It costs nothing, takes a second, and for most everyday jobs the answer is just as good.
What are “smaller” and “faster” settings?
Most AI apps let you choose how hard the AI works, usually from a menu next to the message box. There are two main choices:
- The model. Apps offer a lighter, faster model and one or more larger ones.
- Thinking mode. Also called reasoning. The AI works through a problem step by step before it replies. That helps with hard problems but takes far more work behind the scenes.
Why it matters
Every answer an AI gives uses electricity in a data centre. Bigger models and Thinking modes do much more work for each answer, so they use much more energy.
- Bigger models: the most capable models are estimated to use nearly 4 times the energy of fast ones, on average.
- Thinking mode: in independent tests on open AI models, reasoning used 30 times more energy on average.
One quick question makes little difference on its own. But habits add up across a day, a team and a year, and choosing the right setting is the easiest habit to change.
How to use smaller, faster AI day to day
Start with the fast setting and step up only when you need to. Here’s how in each app. The names change often, so check yours.
- ChatGPT: in the model menu, choose Instant and make sure Thinking is switched off.
- Claude: in the model menu next to the send button, choose Haiku. If you see an Effort setting, set it to Low.
- Gemini: choose Flash or Flash-Lite, and leave the thinking level on Low, which is the default.
- Copilot: choose Quick response rather than Think Deeper.
Then:
- Step up only if you need to. If the answer isn’t good enough, try again with a bigger model or Thinking on.
- Go back to the fast setting for your next everyday task.
- Save the big models for hard problems. Complex analysis, maths and multi-step research.
Which setting for which job?
| Job | Setting |
|---|---|
| Tidy or rewrite an email | Fast, Thinking off |
| Summarise a document | Fast, Thinking off |
| Brainstorm ideas | Fast, Thinking off |
| Hard maths or data analysis | Thinking on, or a bigger model |
| Complex research | Bigger model with Thinking on |
What we don’t know yet
AI companies don’t publish energy figures for each setting, so the numbers above are independent estimates, not exact measurements. Those estimates are improving all the time, and we’ll update this guide as they do.
It’s also worth remembering that easier AI can mean more AI. Choosing a smaller model helps most when we keep asking whether we need AI for the task at all.
Frequently asked questions
Is ChatGPT Instant greener than Thinking?
We don’t know for certain. OpenAI doesn’t publish energy figures for Instant or Thinking, and nobody outside the company has measured them. But related research points the same way: estimates suggest top-tier models use nearly 4 times the energy of fast, lightweight ones, and tests on open AI models found reasoning used 30 times more energy on average. So Instant is likely the greener choice for everyday tasks, but that’s an informed judgement, not a measurement.
Is a smaller model less accurate?
For hard problems, often yes. For everyday jobs like rewriting, summarising and brainstorming, a fast model usually does just as well.
What if my app chooses the model for me?
Settings like Auto in Gemini or Smart in Copilot pick a model for each question. They’re convenient, but you can’t see which model answered. If you want to be sure, choose the fast option yourself.
Getting started
Next time you open your AI app, check the setting before you type. Start small, step up when you need to, and let the habit grow from there.
For more simple ways to get good answers with less waste, try our free Green AI Prompting Guide. If your team is working out how to use AI well, add model choice to your responsible AI policy, or book a free call and we can talk it through.