AI Voice Agent Comparison 2026: ElevenLabs, Retell AI, Vapi and 7 More (Pricing & Free Plans)

If you are considering an AI voice agent, choosing the right tool from dozens of options is not easy. In particular, pricing, free plan availability, Japanese support quality, and platforms matter differently depending on your use case.

This article compares 10 major tools, including ElevenLabs Voice Agent and Retell AI. Based on AIpedia data (as of November 2026), we outline the strengths and weaknesses of each tool. We also clarify differences based on goals, such as whether a tool is for developers or no-code users, or for businesses or individuals.

We also give tips for choosing and recommendations by goal for different business workflows. Use this as a reference when comparing options before adoption or checking compatibility with existing systems. Please verify the latest pricing and feature details on each official website.

What Is an AI Voice Agent? Capabilities and Key Considerations Before Choosing

An AI voice agent is an AI system that uses speech recognition and synthesis technologies to hold human-like conversations over phone or web. Unlike traditional IVR (voice menus), it can understand context and provide natural responses.

• Automating customer support: It answers frequently asked questions and verifies inquiry details 24/7.
• Handling reservations and intake: With calendar integration, it smoothly checks availability and arranges bookings.
• Making outbound calls: It delivers customer guidance and reminders at scale with consistent quality.
• Integrating with backend systems: It connects to CRMs and external APIs to update or retrieve information during calls.

When choosing a tool, first check the "free tier" limits. For example, ElevenLabs Voice Agent and Vapi offer free tiers, Retell AI provides $10 in credits, and Deepgram offers $200 in free credits. In contrast, Synthflow AI only offers paid plans.

Next, the "level of Japanese support" is crucial. Many tools support Japanese only partially, and quality may be lower than in English. Parloa does not support Japanese, so it is not an option for calls in Japanese. Finally, check the "target user base." Vocode and Retell AI feature developer-oriented API designs, while Synthflow AI and ElevenLabs Voice Agent allow no-code construction, making them easy to adopt even without technical knowledge.

Comparison of Top 10 Tools (Pricing, Japanese Support, Platforms)

Tool	AIpedia rating	Main plans	Japanese support	Platforms
ElevenLabs Voice Agent	4.4	Free tier available / Starter $5/month / Scale $22/month	Partial support	Web, API
Retell AI	4.3	Free tier ($10 credit) / Pay-as-you-go $0.07-0.20/minute / Enterprise (contact sales)	Partial support	Web, API
Vapi	4.2	Free tier (10 minutes/month) / Pay As You Go: $0.05/minute / Growth $0.05/minute + $100/month	Partial support	Web, API
Bland AI	4.3	Pay-as-you-go from $0.09/minute / Enterprise (contact sales) (volume discounts available)	Partial support	API, Web
Synthflow AI	4.2	Starter $29/month (50 minutes of calls) / Pro $450/month (2,000 minutes) / Growth $900/month (4,000 minutes) / Agency (contact sales)	Partial support	Web, API
PolyAI	4.2	Custom quote for Enterprise	Partial support	Web, Phone line integration
Parloa	4.1	Enterprise (contact sales) (annual contract basis) / Custom quote / Free demo available	No support	Web, API
Cognigy	4	Enterprise (contact sales)	Partial support	Web, API, Phone line integration
Deepgram	4.3	Free tier ($200 credit) / Pay As You Go: STT from $0.0043/minute / TTS from $0.015/1000 characters	Partial support	API, Web
Vocode	4.1	Open source: free / Hosted API from $0.05/minute / Enterprise (contact sales)	Partial support	Web, API, Self-hosted

Ratings are out of 5 points by the AIpedia editorial team. Pricing and plans may change. Please check the official website of each tool for the latest information before signing a contract.

Features, Pricing, and Best Use Cases for 10 Tools

1. ElevenLabs Voice Agent

ElevenLabs Voice Agent is an AI voice agent building platform that leverages ElevenLabs' speech synthesis technology. It integrates speech recognition with LLMs to achieve low-latency, emotionally rich phone interactions. It supports business automation for tasks such as customer support and appointment scheduling.

• Strengths: Supports 29 languages and can handle interactions with natural-sounding voice.
• Strengths: Features a no-code builder UI, allowing you to build agents without programming knowledge.
• Strengths: Integrates with phone lines from providers like Twilio, enabling operation on existing phone numbers.
• Things to note: ElevenLabs voice API fees are added, which can easily increase costs.
• Things to note: While Japanese is supported, quality may vary compared to English.

Pricing: Free tier available / Starter $5/month / Scale $22/month / Business $99/month / Enterprise (contact sales)

Best for: Those who prioritize natural voice quality and want to easily start automating phone support with no-code tools. However, designing complex conversation flows requires expertise, so sufficient design consideration is needed before implementation.

2. Retell AI

Retell AI is a platform that allows developers to quickly build and deploy AI voice agents. Using proprietary technology, it starts responding within 800 milliseconds of the user's utterance. This achieves natural voice AI close to human conversation tempo.

• Strengths: Ultra-low latency (under 800ms) significantly reduces the time the phone counterpart feels silence.
• Strengths: Supports Python and TypeScript SDKs, allowing deployment with just a few lines of code.
• Strengths: Natively integrates with existing communication infrastructure like Twilio or Vonage.
• Things to note: Designed for developers, so programming knowledge is required.
• Things to note: Japanese voice quality and recognition accuracy may be slightly inferior compared to English.

Pricing: Free tier ($10 credit) / Pay-as-you-go $0.07-0.20/minute / Enterprise (contact sales)

Best for: Developers who want flexible customization via code, and businesses looking to quickly implement AI phone support into existing communication infrastructure. It is intended for use cases where natural conversation tempo is important, such as medical appointments or customer support.

View detailed features, pricing, and FAQ for Retell AI

3. Vapi

Vapi is a platform that allows you to build AI voice agents with low-code. It enables 24/7 automated handling of voice AI tasks such as phone interactions and customer support. It integrates with major AI models to provide a natural conversation experience.

• Strengths: Responds with low latency under 500ms, enabling real-time conversations.
• Strengths: Easy integration with phone line services like Twilio.
• Things to note: Japanese speech recognition and synthesis quality may be inferior compared to English.

Pricing: Free tier (10 minutes/month) / Pay As You Go: $0.05/minute / Growth $0.05/minute+$100/month / Enterprise (contact sales)

Best for: Those who want to connect an AI agent to an existing phone number, or those who want to start voice automation with low-code. Building complex flows requires technical knowledge, making it best for companies with development resources.

4. Bland AI

Bland AI is an AI phone agent platform for developers. Its API-first design lets you implement natural AI calls with just a few lines of code. Proprietary voice synthesis technology minimizes latency to enable real-time conversation.

• Strengths: It claims near-human natural call quality.
• Strengths: Pay-as-you-go pricing ($0.09/minute~) scales to thousands of simultaneous calls.
• Strengths: Supports advanced workflows, such as external API calls and CRM updates during calls.
• Things to note: Programming or API knowledge is required, and the no-code management interface is limited.
• Things to note: Japanese support is limited, and calls in English offer the highest quality.

Pricing: Pay-as-you-go $0.09/minute~ / Enterprise (contact sales; volume discounts available)

Best for: Development teams or businesses aiming to automate large-scale phone operations based on API integration. However, if considering use in Japanese, you need to verify the scope of support.

5. Synthflow AI

Synthflow AI is a platform that lets you build AI voice agents using a no-code visual builder. It automates phone support, appointment management, and customer service 24/7. It supports both inbound and outbound calls.

• Strengths: You can build and deploy agents in minutes without programming knowledge.
• Strengths: Offers robust integrations with CRMs like HubSpot and Salesforce, calendars, and Twilio.
• Things to note: Japanese voice quality and recognition accuracy may be slightly lower than English.
• Things to note: Billing is based on call minutes, so costs can add up with heavy usage.

Pricing: Starter $29/month (50 minutes of calls), Pro $450/month (2,000 minutes), Growth $900/month (4,000 minutes), Agency (contact sales).

Best for: Businesses where marketing or sales teams want to implement AI phone support that easily integrates into existing workflows. However, if considering primary use in Japanese, we recommend testing it beforehand.

6. PolyAI

PolyAI is an enterprise-grade conversational AI voice agent platform. It replaces traditional IVR systems to automate customer support phone handling 24/7. Adoption is growing in industries with high volumes of phone inquiries, such as hotels and finance.

• Strengths: Can execute complex processes requiring backend system integration, such as reservation changes and order tracking, in real time.
• Strengths: Maintains context even if users change topics, enabling natural voice responses aligned with brand tone.
• Strengths: Call analytics dashboards show resolution rates and customer satisfaction, so you can keep improving the service.
• Things to note: As it is enterprise-focused, costs may be high for small and medium-sized businesses.
• Things to note: Self-service setup is not possible; implementation support by a specialized team is required.

Pricing: Custom quote for Enterprise

Best for: Large enterprises with high volumes of phone inquiries seeking advanced conversation management and integration with existing systems. Implementation takes 6–8 weeks, so careful scheduling is needed. Japanese support is available, but accuracy may differ from English; please consult individually regarding specific requirements.

7. Parloa

Parloa is an enterprise AI agent management platform. It centrally manages multi-channel support across phone, chat, and messaging to enable automation in large enterprise contact centers. Parloa partners with Microsoft and offers deep integration with Azure OpenAI Service.

• Strengths: Monitors AI response quality in real time and automatically performs hallucination detection and compliance checks.
• Strengths: Integrates with existing systems such as Genesys Cloud CX and Salesforce, enabling gradual AI adoption.
• Things to note: Pricing is based on custom quotes for enterprises and is not publicly disclosed.
• Things to note: No Japanese support; primarily supports European languages such as English and German.

Pricing: Enterprise (contact sales; annual contract basis) / Custom quote / Free demo available

Best for: Enterprises operating large-scale contact centers that require strict quality control and security standards. Particularly suitable for organizations in finance, telecommunications, and retail that need to handle a high volume of customer inquiries.

View detailed features, pricing, and FAQ for Parloa

8. Cognigy

Cognigy is a German enterprise conversational AI platform. In 2025, it was announced that NICE, a major contact center software provider, would acquire Cognigy. It specializes in contact center automation, streamlining customer support across all channels, including phone and chat. Its key feature is the integrated management of automated voice calls and chatbots.

• Strengths: Integrates and manages voice AI and chatbots on a single platform. Natively supports over 25 languages, enabling multilingual support.
• Strengths: Complies with GDPR and prioritizes data privacy. Supports integration with major contact center systems such as Genesys and Avaya.
• Things to note: As an enterprise solution, pricing tends to be high. Features and scale may be excessive for small and medium-sized businesses.
• Things to note: While Japanese bots can be created, the management interface is available only in English and German. Support infrastructure and agents within Japan are limited.

Pricing: Enterprise (contact sales)

Best for: Enterprises operating large-scale contact centers or global companies requiring multilingual customer support. Particularly suitable for services targeting the European market where GDPR compliance is mandatory.

9. Deepgram

Deepgram is a platform providing speech recognition and synthesis APIs. It achieves high-accuracy speech recognition and low latency using proprietary deep learning models. It specializes in building real-time conversational AI and voice agents, achieving end-to-end latency of under 100ms.

• Strengths: Features the Nova-3 model, which boasts high recognition accuracy, and low latency of under 100ms. Additionally, using the Agent API allows for easy construction of voice agents involving LLM integration and phone line connectivity.
• Strengths: Supports 36 languages and includes advanced speech analysis features such as speaker diarization and emotion detection. Furthermore, $200 in free credits is available, allowing for sufficient trial use.
• Things to note: As a developer-focused API, basic programming knowledge is required. Note that no GUI-based no-code builder is provided.
• Things to note: Japanese recognition accuracy may be lower than English. Also, since it uses a pay-as-you-go model, costs may increase with high usage volumes.

Pricing: Free tier ($200 credit) / Pay As You Go: STT from $0.0043/minute / TTS from $0.015/1000 characters / Growth and Enterprise (contact sales)

Best for: Developers and businesses with programming knowledge who want to build high-performance voice agents via API. Especially recommended for those considering automation of customer support or reservation intake that requires real-time audio processing.

10. Vocode

Vocode is an open-source voice AI agent building framework for developers. By freely combining speech recognition, large language models, and speech synthesis, you can build custom voice agents. It supports integration with phone, web, and mobile apps.

• Strengths: Flexible modularity to combine STT, LLM, and TTS.
• Strengths: Released under the Apache 2.0 license, allowing self-hosting.
• Strengths: SDKs for Python and TypeScript are provided, enabling rapid prototyping.
• Things to note: Programming knowledge is required; there is no no-code GUI builder.
• Things to note: Self-hosting requires knowledge of infrastructure setup and operations.

Pricing: The open-source version is free. The hosted API starts at $0.05/minute, and Enterprise is available on request (contact sales).

Best for: Developers with Python or TypeScript experience who must handle voice data under strict regulations, and developers who want flexible integration with existing systems.

View detailed features, pricing, and FAQ for Vocode

Recommendations by Goal

Goal	Recommended	Reason
Want to try it for free first	Deepgram	$200 in free credits is provided, allowing for sufficient trial use.
Want to build easily without code	Synthflow AI, ElevenLabs Voice Agent	Both feature no-code builders, enabling agent creation without programming knowledge.
Developer wanting to integrate via API	Retell AI, Vocode	Python and TypeScript SDKs are provided, allowing customization within the codebase.
Want to deploy at enterprise scale	PolyAI, Cognigy	Features for large-scale contact centers and a track record of integration with major systems.
Want to start with pay-as-you-go based on call volume	Vapi, Bland AI	Vapi offers pay-as-you-go starting at $0.05/minute, and Bland AI starting at $0.09/minute. Costs increase with call volume, so obtaining a quote is necessary.
Want to prioritize quality control in large European contact centers	Parloa	Monitors AI responses in real time and automatically detects hallucinations and checks compliance (no Japanese support).
Want to prioritize speech recognition accuracy	Deepgram	Can use the Nova-3 model, which boasts high recognition accuracy (Japanese accuracy is lower compared to English).

The table above provides general guidelines based on the characteristics of each tool. When implementing in actual business operations, please evaluate according to your company's budget and technical infrastructure. We recommend checking the official websites of each service for the latest pricing plans and feature details.

How to Choose Without Regrets

Check the differences in pricing structures

Billing models vary significantly by tool. ElevenLabs Voice Agent and Synthflow AI use a monthly flat-rate model, while Retell AI and Vapi use usage-based billing based on call duration.

In particular, Vapi tends to see costs spike rapidly as call volume increases, so you need to choose a plan that matches your expected usage frequency. Some tools, such as PolyAI and Parloa, are enterprise-focused and only offer custom quotes. It is safer to set a budget cap in advance.

Prioritize the quality of Japanese support

In many tools, Japanese is listed as "partially supported" or "limited support." ElevenLabs Voice Agent supports 29 languages, but its quality is considered lower compared to English.

Similarly, Retell AI and Bland AI are considered higher quality in English. If natural interaction in Japanese is essential, it is important to verify this by listening to and comparing actual voice samples.

Consider your development environment and technical capabilities

Some tools can be built without code, while others require API integration. ElevenLabs Voice Agent and Synthflow AI feature no-code builders, allowing use without programming knowledge.

On the other hand, Retell AI and Vocode are developer-focused and require implementation using SDKs for Python or TypeScript. Based on your team's technical skills, decide whether to choose an open-source version like Vocode that supports self-hosting, or to use a hosted service.

Match the scale of your deployment

The features and support provided differ between tools for individuals and small-to-medium businesses versus those for large enterprises. Cognigy and Parloa are enterprise-focused and assume specialized consulting and long-term contracts.

For small-to-medium businesses, costs may be too high or implementation may take too long. A phased approach is effective: start by experimenting with tools that offer a free plan, such as ElevenLabs Voice Agent or Deepgram, and migrate to a larger-scale system as needed.

FAQ

Q. Do AI voice agents support Japanese?

Many tools support Japanese, but quality varies. ElevenLabs Voice Agent and Synthflow AI are listed as having partial support. In contrast, Parloa is noted as not supporting it. Also, note that with Retell AI and Vapi, recognition accuracy and naturalness may be lower compared to English.

Q. Can I build one without programming knowledge?

ElevenLabs Voice Agent and Synthflow AI feature no-code builders. This allows you to create agents without coding. On the other hand, Retell AI and Bland AI use an API-first design. Using these tools requires programming knowledge in Python or TypeScript.

Q. Is there a free plan available?

ElevenLabs Voice Agent offers a free tier. Retell AI provides $10 in free credits, and Vapi allows up to 10 minutes of free usage per month. Deepgram also offers $200 in free credits. However, some tools like Synthflow AI and PolyAI only offer paid plans.

Q. Can I integrate with phone lines?

Many tools can integrate with communication infrastructure like Twilio. ElevenLabs Voice Agent, Retell AI, and Vapi all support phone line integration. PolyAI and Cognigy also feature phone line connectivity as a main function. This allows you to implement AI handling using existing phone numbers.

Q. How long does it take to implement?

It varies greatly by tool. Vapi and Synthflow AI support low-code and no-code approaches. You may be able to start building in a relatively short time. In contrast, PolyAI is noted as taking 6–8 weeks for implementation. Enterprise-oriented tools like Parloa and Cognigy require custom quotes or consulting.

Summary

This comparison organized 10 tools, including ElevenLabs Voice Agent and Retell AI, based on pricing, features, and Japanese support. The tools vary between developer-focused API types and no-code builder types, resulting in differences in ease of implementation and customization flexibility. Additionally, Japanese voice quality tends to be inferior to English across multiple tools, making pre-deployment verification important.

In terms of cost, many tools offer free tiers or pay-as-you-go pricing, while enterprise-focused custom quote models also exist, such as PolyAI and Parloa. Checking unit prices for increased call volumes and additional fees for external API integrations in advance is key to preventing unexpected cost increases.

• If you prioritize natural voice quality, choose ElevenLabs Voice Agent (emotional expression and high-quality speech synthesis)
• If developers want to build with low latency, choose Retell AI (response speed under 800ms and flexibility via SDK)
• If you want to start easily without code, choose Synthflow AI (GUI-based building and robust CRM integration)