AI receptionist platforms compared: Retell AI, Vapi and Synthflow in 2026

Is Retell, Vapi or Synthflow a ready-made AI receptionist?

No. All three are platforms for building an AI voice agent. You get the engine: a language model, a synthetic voice, speech transcription and a phone connection. You still have to write what the agent says, decide when it transfers a call, connect your calendar or CRM, and test it on real calls.

That matters if you are a small business looking for an “AI receptionist” that answers the phone tomorrow morning. None of these three tools is a plug-in switchboard. What differs is how much of the assembly is left to you: little with Synthflow, which includes launch support in its contracts; a fair amount with Retell; the most with Vapi, which is built for developers working through an API.

What goes into the cost of one minute of an AI call?

A voice agent stacks four paid components on every call minute:

• The language model, which decides what to answer.
• The voice, which turns the answer into speech.
• Transcription, which turns the caller’s words into text.
• Telephony, the phone number and the line that carries the call.

Each platform bills these layers differently:

The practical consequence: Retell gives you a published range, so you can estimate a budget before building anything. Vapi shows only its own share, and you have to add up each provider yourself. Synthflow publishes no per-minute price at all.

How much do Retell AI, Vapi and Synthflow cost in 2026?

These prices were read on each official pricing page on 23 September 2026.

Retell AI has no subscription. You pay 0.07 to 0.31 USD per minute depending on the model, the voice and the telephony, with 10 USD in credits at sign-up. For 1,000 minutes of calls a month, that works out to between 70 and 310 USD, plus 2 USD per phone number. The Enterprise plan adds volume pricing, SSO and 24/7 support, on quote.

Vapi starts without a plan: 5 USD in credits, then 0.05 USD per minute of hosting plus provider costs. The Core plan costs 29 USD a month on top of usage and raises the limits to 10 concurrent calls and 30 days of data retention. Pro costs 10% of hosting fees with a minimum of 999 USD a month. Premier is on quote.

Synthflow lists only enterprise contracts, from 30,000 USD a year, which is 2,500 USD a month at minimum. There is no free plan and no trial mentioned.

Retell vs Vapi: which one should you start with?

Our reading: Retell is easier to start with, Vapi goes further. Retell’s single per-minute range and its 20 included concurrent calls make it possible to test a receptionist without a contract and without doing arithmetic across five invoices. Its weak point is support, limited to the community and email outside Enterprise.

Vapi lets you choose every building block: the model, the voice, the transcription. Models are re-billed without markup. In exchange, its ease of use scores 2.5 out of 5 on our grid, against 3.5 for Retell, because everything has to be assembled.

The step to watch at Vapi is the jump from Core at 29 USD to Pro at a 999 USD minimum. Pro brings 30 concurrent calls, 180 days of retention, role-based access and a 99% uptime SLA. A team that only needs more than 10 simultaneous calls has no plan in between.

Overall scores on our grid: Vapi 3.7, Retell AI 3.6, Synthflow 2.9. Synthflow loses points on price and on the absence of a free option, not on features.

Where is call data stored, and does it matter?

A receptionist records names, phone numbers and sometimes health or payment details. Where that data lives is a real question, not a formality.

• Retell AI processes and stores data in the United States on AWS. Its documentation says it does not yet operate services in the EU. It holds SOC 2 Type 1 and Type 2 and HIPAA, and offers a DPA with EU Standard Contractual Clauses, signable online at no cost. Retention can be set per agent, from 1 day to 2 years.
• Vapi runs on AWS with deployments in the United States and the EU. Each organization belongs to one region. The Trust Center lists SOC 2 Type II, SOC 3, HIPAA, GDPR, CCPA and PCI DSS. The HIPAA option with a standard BAA costs 2,000 USD a month.
• Synthflow announces SOC 2 Type 2, ISO/IEC 27001, ISO/IEC 42001, HIPAA, GDPR and PCI DSS, with a DPA on request. Its hosting region is not published on the pages we checked.

If you serve European customers, Vapi is the only one of the three with a documented EU region.

What do you need before choosing?

Three questions settle most of the choice.

Skills. Is there someone who can configure an agent, write prompts and connect an API? If not, Retell is the gentler start, and Synthflow the only one that sells guided deployment, at 30,000 USD a year minimum. Vapi assumes a developer.

Call volume. Count your monthly minutes and your peak of simultaneous calls. At a few hundred minutes, per-minute billing at Retell or Vapi stays small. Above 10 simultaneous calls, Vapi pushes you toward the 999 USD plan, while Retell includes 20.

Data. Decide whether call data may leave your region. If it must stay in the EU, Retell is ruled out today. If you handle health data in the United States, check the HIPAA terms: included at Retell, 2,000 USD a month at Vapi.

Which platform fits which case?

For a small business testing an AI receptionist on a single line, start with Retell’s 10 USD of credits. For a product team building voice into its own software, Vapi gives the most control. For a contact center with a yearly budget and a need for support, Synthflow is the only one of the three that sells a supported rollout.