Lesson 6: Behind the Scenes
Costs of model training
Training a model can take weeks or months. Epoch estimates it took 3 months to train GPT-4. Above are estimated costs for the electricity and hardware to run the model training, not including the teams of engineers, data collection or years of research. (From Stanford AI Index 2025 and Epoch AI).
What does the money pay for? The table below shows the components that make up the highest costs for training LLMs.
| Cost component | Description |
|---|---|
| GPUs | Thousands of specialised AI chips running 24/7 for months - each costing $25,000+ |
| Electricity | Running and cooling all those chips uses as much power as a small town. |
| Engineers | Teams of researchers and engineers, often for years, before training even begins. |
| Data | Collecting, cleaning, and licensing the billions of pages of text used for training. |