Break-even index / RTX 4090 / GPT-5.4 / Rhode Island
Will a New RTX 4090 build beat GPT-5.4 in Rhode Island?
Break-even lands around month 20. Real, but slow — a hybrid setup (local for the routine work, cloud for the peaks) usually beats going all-in.
How to read it: OWN — the rig pays for itself inside 18 months. HYBRID — break-even lands between 18 and 36 months; real, but slow. RENT — it never pays off before the hardware is due for replacement. Every formula and threshold is public on the methodology page.
The numbers
| Build cost (New RTX 4090 build) | $2,300 ($2,000–$2,600) |
|---|---|
| Hardware amortized (3 yr) | $63.89/mo |
| Electricity in Rhode Island ($0.301/kWh) | $16.03/mo (53.25 kWh) |
| Local total cost of ownership | $79.92/mo |
| GPT-5.4 at the same usage | $131/mo |
| Break-even | about 20 months |
Assumes the "coding assistant" preset: ~15M tokens/month, 3 h/day active, 5 h/day idle. GPT-5.4 priced at $2.5/M in, $15/M out (verified 2026-07-05). Rig ceiling: 70B at Q4, faster prompt processing. Jargon: VRAM is the GPU memory that decides which models fit; Q4 is 4-bit quantization — a smaller, faster copy of a model with a slight quality cost.
See your verdict — then tweak every number →