Key Takeaways
- RTX 4090: 575W. Needs 1200W PSU, excellent case airflow.
- RTX 4080: 320W. Needs 850W PSU, good airflow.
- RTX 4070 Ti: 290W. Needs 750W PSU, adequate airflow.
- M3 Max Mac: 25–35W for inference (extremely efficient).
- Running 24/7 costs: RTX 4090 = $50–70/month, RTX 4070 Ti = $20–25/month.
- As of April 2026, cooling is critical. Poor airflow reduces lifespan and throttles performance.
GPU Power Draw at Full Load
| GPU | Full Load Power | Idle Power | PSU Needed |
|---|---|---|---|
| RTX 5090 | — | — | — |
| RTX 4090 | — | — | — |
| RTX 4080 | — | — | — |
| RTX 4070 Ti | — | — | — |
| RTX 4070 | — | — | — |
| M3 Max Mac (GPU) | — | — | — |
Total System Power Requirements
The GPU is not the only power consumer. Factor in CPU, RAM, storage, and motherboard:
| Component | Power | Notes |
|---|---|---|
| GPU (RTX 4090) | 575W | Peaks at 100% utilization |
| CPU (Ryzen 9 7950X) | 170W | Under load |
| Motherboard + RAM + SSD | 100W | Typical |
| Cooling fans, PSU overhead | 50–100W | Safety margin |
| Total | — | Needs 1200W PSU |
Cost of Electricity to Run 24/7
Assuming $0.12/kWh (US average):
| GPU | Daily Cost | Monthly Cost | Annual Cost |
|---|---|---|---|
| RTX 4090 (600W avg) | $1.73 | — | — |
| RTX 4080 (350W avg) | $1.01 | — | — |
| RTX 4070 Ti (300W avg) | $0.86 | — | — |
| M3 Max Mac (30W avg) | $0.09 | — | — |
Cooling Requirements
Proper cooling is critical for GPU lifespan (5+ years) and preventing thermal throttling.
Adequate case airflow: Front fans pull cool air in, rear/top fans exhaust hot air. RTX 4090 needs large case with 3+ fans.
Ambient temperature: Ideally 18–24°C. In hot climates (30°C+), cooling becomes critical.
Thermal paste: Replace every 2–3 years for optimal heat transfer (if applicable).
Monitoring: Use GPU-Z or nvidia-smi to monitor temperatures. Keep under 80°C sustained.
Common Power and Cooling Mistakes
- Undersizing the PSU. RTX 4090 with 750W PSU will trigger shutdowns under load. Always budget 2× the GPU power draw.
- Ignoring case airflow. Poor airflow causes thermal throttling (~10% performance loss) and shortens GPU lifespan.
- Running 24/7 without considering costs. RTX 4090 costs $50/month electricity. Not practical for personal use unless you run inference constantly.
- Not monitoring GPU temperature. Cards can silently throttle due to thermal stress. Monitor with nvidia-smi.
Sources
- NVIDIA GPU Power Specs — nvidia.com/en-us/geforce
- US Electricity Rates — eia.gov/electricity
- GPU Temperature Monitoring — nvidia.com/en-us/drivers/