Retell AI vs Synthflow
Retell AI charges usage-based and Synthflow charges usage-based. Here's how they compare on price, features and compliance, using each vendor's own published information.
Checked October 15, 2026 (Retell AI) and October 15, 2026 (Synthflow)
| Detail | Retell AI | Synthflow |
|---|---|---|
| Charges by | Usage-based | Usage-based |
| Starts at | Free tier | $2,500/mo |
| Includes | $10 in free credits; 20 concurrent calls at no charge | — |
| Overage | — | — |
| Per minute | $0.07 | — |
| Free trial | $10 in free credits on sign-up | — |
| How it works | AI only | AI only |
| Answers inbound calls | Yes | Yes |
| Places outbound calls | Yes | Yes |
| Books appointments | Yes | Yes |
| Warm transfer to a person | Yes | Yes |
| Text follow-up | Yes | Yes |
| Call recording | Yes | Yes |
| Transcripts | Yes | Yes |
| CRM sync | Yes | Yes |
| Keep your number (porting) | Unconfirmed | Unconfirmed |
| Spanish | Yes | Yes |
| Other languages | Yes | Yes |
| Web chat | Yes | Yes |
| API | Yes | Yes |
| Custom voice | Yes | Yes |
| Signs a HIPAA BAA | Yes | Yes |
| SOC 2 | SOC 2 Type II | SOC 2 Type II |
Integrations
Both list: GoHighLevel, HubSpot, Zoho CRM, Salesforce, Monday.com, Airtable, Pipedrive, Cal.com, Twilio, Vonage, Telnyx, Five9, RingCentral, Make, n8n, Zapier, Zendesk, Intercom, WhatsApp, Dentrix, Shopify, Stripe, ServiceTitan.
Only Retell AI: Microsoft Dynamics 365, Keap, Smartsheet, Calendly, NICE, Talkdesk, LiveVox, Amazon Connect, Freshdesk, Slack, Microsoft Teams, Jane App, Open Dental, Epic, ChiroTouch, QuickBooks, Xero, DATEV, Google Workspace, DocuSign, ServiceNow, ClickUp, Asana.
Only Synthflow: Google Calendar, Outlook Calendar, 8x8, Genesys, OpenPhone, Dialpad, 3CX, JustCall, CloudTalk, Cisco, Avaya, Intermedia, Freshworks, ActiveCampaign, Jobber, Follow Up Boss, Housecall Pro, Velocify, Practice Better, Bitrix24, athenaOne, Clay, Apollo.io, Gong, Outreach, Asterisk, GoTo, Plivo, Ooma, Activepieces.
Pricing notes
Retell AI: Retell lists voice agents at $0.07-$0.31 per minute, built from separate components. Its default calculator setup totals $0.11/min: Retell voice infrastructure $0.055/min, LLM $0.04/min, TTS $0.015/min, telephony $0.00. LLM is billed per minute by model (from $0.0016/min to $0.64/min on the listed models). TTS is $0.015/min for Retell, MiniMax, Fish, Cartesia, OpenAI and Inworld voices, and $0.04-$0.10/min for ElevenLabs voices. Telephony through Retell (Twilio or Telnyx) is $0.015/min; SIP trunking or custom telephony has no Retell telephony charge. Per-call add-ons: knowledge base +$0.005/min, batch call +$0.005/dial, branded call +$0.10 per outbound call, advanced denoising +$0.005/min, safety guardrails +$0.005/min, PII removal +$0.01/min, AI quality assurance $0.10/min after 100 free minutes, SMS $0.01/message. Monthly items: Retell phone numbers $2/month, Retell SMS $20/month, concurrency beyond 20 at $8 per concurrent call per month, knowledge bases beyond 10 at $8 each per month, verified phone number $10/number. Calls are billed to the second; after a transfer the AI fee stops but telephony continues; silence and hold time are billed; failed calls are not billed.
Synthflow: Synthflow's pricing page lists only an Enterprise offering: 'Enterprise contracts start at $30,000 annually' (shown here as $2,500/month, our conversion of the annual minimum). No per-minute rate is published. Telephony (Synthflow native telephony, SIP trunking or approved enterprise telephony), concurrency planning, integrations and launch support are scoped into the contract. The homepage FAQ separately says agents can be built for free and that launched agents move to pay-as-you-go billing for calls and chats. Synthflow's usage docs say calls are billed per second (rounded up), no-answer and voicemail hang-ups count as 5 seconds, failed calls are not billed, usage after a transfer is not counted, and 5 chat messages count as 1 usage minute. Rates come from each customer's agreement.
Full profiles: Retell AI and Synthflow, with sources linked.