Retell AI vs Synthflow (2026): which should you pick?

Pick Retell AI if

• Fits if you want to pay per minute with no monthly commitment
• Works for developers wiring phone agents into Twilio or HubSpot

Look elsewhere if

• Pricey if you add it up, as model, voice and telephony sit on top of the $0.055 base
• Watch out: HIPAA and BAA, SSO, role-based access and custom retention are Enterprise only
• Watch out: AI quality assurance and PII removal are charged per minute on top
• Not for you if you want a fixed bill, because cost moves with minutes

Pick Synthflow if

• Fits if you want white-label voice agents under one annual contract
• Makes sense if you use Five9, Salesforce or HubSpot

Look elsewhere if

• Not for you if you want to try it, as the page says no free plan and no trial
• Skip it if you are a small business, since every deployment starts on an Enterprise contract
• Not for you if you want per-minute pricing, because the page says there is none
• Watch out: HIPAA is self-attested in the vendor's own Trust Center summary

Retell AI

• The rate is a sum of parts: voice infrastructure is $0.055 per minute, with model, voice and telephony on top, hence $0.07 to $0.31.
• The comparison table lists HIPAA and BAA, SSO, role-based access and custom data retention for Enterprise only.
• Dedicated implementation support and a dedicated stable server are Enterprise add-ons.
• Add-ons such as AI quality assurance and PII removal are charged per minute on top of the base rate.

Synthflow

• No prices are published. The pricing page says it is an annual enterprise agreement with no free plan, no trial and no per-minute rate.
• Every new deployment starts on an Enterprise contract, so it is not set up for self-serve small-business use.
• HIPAA is listed as self-attested in the vendor's own Trust Center summary.

Retell AI

Inbound and outbound phone agents

Agents answer or place calls, transfer to a human, book appointments, use a knowledge base and navigate keypad menus.

Batch calls and caller ID

The deploy menu lists batch calling for high-volume campaigns, branded caller ID and verified phone numbers.

Testing and monitoring

Simulation testing, call transcripts and analytics, post-call analysis and AI quality assurance are listed for monitoring agents.

Model and voice choice

The cost estimator offers language models from OpenAI, Anthropic and Google and voices from Retell, ElevenLabs, Cartesia, Minimax, Fish and OpenAI.

Chat agents

The same platform runs chat agents, priced from $0.002 per message.

Synthflow

Voice agents for calls

Agents handle customer service, reception, answering service, concierge, appointment booking and IVR use cases over the phone.

Telephony options

The contract can use Synthflow Native Telephony, SIP trunking or approved enterprise telephony, with routing, escalation and fallback logic.

White label

BPOs and software platforms can run it under their own brand, with a workspace per client and one analytics dashboard across them.

Launch support

Where the agreement includes it, Synthflow's forward-deployed engineers implement, test and launch agents with your team. Deployments go live in weeks.

Security and compliance

The Trust Center lists SOC 2 Type 2, ISO 27001, GDPR, HIPAA (self-attested) and PCI DSS v4.0.1, with ISO 42001, DORA and the EU AI Act in progress.

Retell AI

• Pay as you go$0

  to start, then $0.07-$0.31 per minute

  Voice agents at $0.07-$0.31 per minute, chat agents from $0.002 per message, 20 free concurrent calls, API access and email support.

• EnterpriseCustom

  Custom voice and chat pricing, role-based access, custom SSO, MSA, DPA and BAA terms, and 24/7 support with a dedicated portal.

Synthflow

Pricing could not be confirmed. See synthflow.ai.