Imagen 4 Fast vs GPT Image 1.5
Google's Imagen 4 Fast and OpenAI's GPT Image 1.5 both target image generation, but they price and behave differently. Here is the side-by-side.
Pricing checked against provider documentation on . How we verify
The short answer
Imagen 4 Fast is the cheaper option — roughly 2.1x less on a blended workload, and it suits cheapest speed-first generation. GPT Image 1.5 justifies its premium when you need complex multi-subject composition.
Google • Imagen 4
$0.02 / $
/ image (input / output)
Google's efficiency tier for image generation, aimed at high-volume pipelines where throughput matters more than the last increment of quality. Fine for thumbnails, placeholders, and drafts; step up to the Gemini image models when typography or compositing is the point.
OpenAI • GPT Image
$0.04 / $
/ image (input / output)
The strongest current model for scenes with many interacting elements — independent testing puts it ahead of the FLUX line on photorealism and well ahead on compositions involving eight or more subjects. Latency is around five seconds, so it is a considered choice rather than an interactive one.
Input price
GPT Image 1.5 is 2.1x the price than Imagen 4 Fast on input tokens.
Specification comparison
| Attribute | Imagen 4 Fast | GPT Image 1.5 |
|---|---|---|
| Input (/ image) | $0.02 | $0.04 |
| Output (/ image) | — | — |
| Cached input | — | — |
| Context window | — | — |
| Max output | — | — |
| Native reasoning | No | No |
| Knowledge cutoff | — | — |
| Relative latency | low | medium |
| Open weights | No | No |
| API model ID | imagen-4.0-fast-generate-001 | gpt-image-1.5 |
| Status | stable | stable |
Imagen 4 Fast: 1K resolution.
GPT Image 1.5: Medium quality at 1024px. High quality is reported between $0.13 and $0.17 per image and sources disagree on the exact figure — confirm in the console before budgeting. A cheaper Mini variant runs about $0.036 at high quality.
Choose Imagen 4 Fast if…
- High-volume thumbnails
- Draft and placeholder imagery
- Rapid prompt iteration
- Catalogue and listing images
Choose GPT Image 1.5 if…
- Complex photorealistic scenes
- Multi-subject compositions
- Editorial and hero imagery
- Iterative image editing
Frequently asked
Is Imagen 4 Fast or GPT Image 1.5 cheaper?
Imagen 4 Fast is cheaper. On a blended 3:1 input-to-output workload it costs about 2.1x less than GPT Image 1.5.
Which has the larger context window, Imagen 4 Fast or GPT Image 1.5?
Both accept up to — tokens, so context is not a differentiator here.
Should I use Imagen 4 Fast or GPT Image 1.5?
Pick Imagen 4 Fast for cheapest speed-first generation. Pick GPT Image 1.5 for complex multi-subject composition. If cost dominates the decision, Imagen 4 Fast wins; if you need the capability ceiling, benchmark both on your own evals before committing.