Stellar vs Retell AI
Stellar vs Retell AI: Business-Ready Agents vs Voice AI Toolkit
Retell AI and Stellar both take voice quality seriously, but they serve different audiences. Retell gives developers a WebSocket-based API for building real-time voice applications with fine-grained control over the conversation pipeline. The developer experience is good, the latency is low, and the documentation is clear. Stellar takes a product-first approach. Instead of giving you building blocks, it gives you finished workflows. You pick a template, answer configuration questions in a visual builder, and your agent is live. Under the hood, Stellar uses GPT Realtime for native speech-to-speech processing, which eliminates the latency penalties of chaining separate STT, LLM, and TTS services.
The verdict
Retell AI builds excellent voice infrastructure with low latency and solid developer tooling. Stellar wraps similar capabilities into a product that non-technical teams can deploy without writing a line of code.
Where Stellar wins
- Zero-code deployment. Visual builder, not API docs.
- GPT Realtime for native speech-to-speech (no STT+LLM+TTS chain latency).
- Three production templates covering the most common SMB voice workflows.
- Google Calendar integration, contact CRM, and call analytics all included.
- TCPA compliance built in: DNC checks, consent tracking, calling hour enforcement.
Where Retell AI wins
- WebSocket-based architecture delivers very low latency for real-time conversations.
- Clean developer experience with well-structured API docs and SDKs.
- Supports custom LLM and voice provider combinations for maximum control.
- Good for building voice AI products (SaaS companies building on top of Retell).
Pricing compared
Retell AI charges per minute with rates that vary based on your chosen providers. Base costs can be competitive, especially if you optimize your LLM and TTS stack. Stellar's pricing is bundled: a 14-day free trial of Growth, then Growth $149/mo (200 min included, $0.18/min overage), Pro $399/mo (750 min included, $0.14/min overage), Scale $899/mo (3,000 min included, $0.11/min overage). Stellar's per-minute rate includes the full product: templates, calendar integration, compliance, CRM, and analytics. With Retell, you pay less per minute but spend engineering hours building everything else.
Switching from Retell AI
Moving from Retell AI to Stellar means transitioning from a code-based integration to a managed product. Your conversation scripts and prompt engineering translate into Stellar's template configuration. The webhook handlers you built for Retell are replaced by Stellar's built-in analytics and routing. Most teams complete the switch in a few hours.
Stellar vs Retell AI: FAQ
Which has lower latency, Stellar or Retell AI?
Both are fast. Retell AI's WebSocket architecture is optimized for minimal round-trip time, and they have done strong work on latency. Stellar uses GPT Realtime, which processes speech-to-speech in a single model pass, avoiding the latency of chaining three separate services. In practice, both deliver sub-second response times. The difference is usually imperceptible to callers.
Can I build a SaaS product on Stellar like I could with Retell?
Retell AI is designed as infrastructure for building voice AI products. If you are a SaaS company creating your own voice application, Retell's API-first approach makes more sense. Stellar is designed for businesses using voice agents, not building voice platforms.
Does Stellar support custom voice providers?
Stellar uses GPT Realtime exclusively, which provides consistent quality across all calls. Retell lets you mix and match STT, LLM, and TTS providers. If you need a very specific voice or model combination, Retell offers more flexibility there.
What happens to my Retell integration if I switch?
Your Retell account and phone numbers remain yours. Stellar provisions new numbers for your agents. You can run both in parallel during transition, then decommission Retell when you are satisfied with Stellar's performance.
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