---
title: "ThunderPhone pricing and usage charges"
description: "Complete ThunderPhone pricing for Spark, Bolt, Storm, voices, languages, prompts, supervision, acknowledgements, calls, hold time, simulations, and phone numbers."
---

Every new account includes **$10 of free call credit** in its first
organization, with no credit card required. Organizations you add later start
without it. The credit pays for any call: browser tests, phone calls, SIP
calls, web and widget calls, and simulations. Calls use the credit first, then
your cash balance. It cannot pay for phone numbers or voice samples, so add
funds with a card when you want a number.


ThunderPhone is prepaid and pay-as-you-go: no subscription and no seat fee.
Calls draw from the selected organization's balance. The agent builder shows
the **all-in per-minute rate** as you change configuration, and Billing History
shows the final charge for each call.

All amounts below are U.S. cents unless stated otherwise.

## Base agent tiers

{/* rate:tiers */}

| Tier | Price | Optimized for |
| --- | ---: | --- |
| **Spark** | **2¢/min** | Cost-efficient, straightforward workflows. |
| **Bolt** | **5¢/min** | Speed and balanced everyday performance. |
| **Storm** | **9¢/min** | Complex prompts, audio understanding, and reasoning. |

{/* /rate */}

Inbound calls, outbound calls, SIP connectivity, web voice widgets, the
standard voice library, supported included languages, simulations and testing
workflows, monitoring, transcripts, transfers, and keypad actions are platform
capabilities rather than separate subscription line items. Usage charges and
the optional additions below still apply.

## Optional per-minute additions

{/* rate:additions */}

| Addition | Price | Notes |
| --- | ---: | --- |
| **Storm verbal acknowledgement** | **+2¢/min** | Spoken filler while the complete response is prepared. None and Tick do not add this charge. |
| **Storm extra intelligence** | **+3¢/min** | Deeper reasoning on Storm. The all-in tier rate becomes 12¢/min before other additions. |
| **Supervision** | **+4¢/min** | Live instruction monitoring. Available on Spark and Storm, not Bolt. |
| **Selected language or premium voice path** | **up to +3¢/min** | The effective speech surcharge is determined by the actual voice-language combination. The language and voice labels do not stack into two separate 3¢ additions. |
| **ThunderPhone-number usage** | **+1¢/min** | Added when a ThunderPhone number carries the call. |
| **Live caller transcripts** | **+1.5¢/min** | Realtime WebSocket API only. Streams caller words while the caller is still speaking, ahead of the settled transcript. Enabled per session with `session.live_transcripts`; see [Live transcripts](/api-reference/realtime#live-transcripts). |

{/* /rate */}

Custom voices can have organization-specific pricing. When one does, the
custom voice policy and builder's all-in rate show the applicable amount.

## Prompt size

{/* rate:prompt */}

The first **5,000 estimated prompt tokens** are included. Each additional block
of **10,000 tokens or part of a block** adds:

| Tier | Surcharge per block |
| --- | ---: |
| Spark | **+1¢/min** |
| Bolt | **+2¢/min** |
| Storm | **+2¢/min** |

For example, a 5,001-token Storm prompt adds 2¢/min; a 15,001-token Storm
prompt adds 4¢/min. The prompt editor displays the estimated size and current
surcharge.

{/* /rate */}

Web-widget `context` is capped at 12,000 characters and is appended to the
prompt used for that session, so it can move a call into a higher prompt-size
block. Call billing metadata breaks out those context tokens.

## Call metering

Normal talk time is measured in **quarter-minute increments** with a minimum of
0.25 billable minutes. Final call charges combine the immutable tier and
options used on that call; changing the agent later does not rewrite history.

Language switching is billed from the language actually spoken in each
segment, when segment information is available. The configured primary
voice-language rate is the fallback.

## Hold time and phone menus

ThunderPhone detects call segments where the agent is not in live
conversation and bills each kind of segment by its own rule:

- **Hold time** is detected automatically and bills at a flat **{/* rate:hold */}2¢/min{/* /rate */} on
  every tier**, no matter how long the queue runs. No tier costs less than
  {/* rate:hold-floor */}2¢/min{/* /rate */}, so hold is always a discount from the agent's normal rate.
- **Automated phone menus (IVR) and call screeners** bill at the agent's
  normal per-minute tier rate.
- **Straight-to-voicemail calls** bill normal quarter-minute metering, capped
  at **one minute at the tier rate**, so a long voicemail greeting cannot run
  up the bill.
- Where a hold segment overlaps a phone-menu segment, the overlap bills as
  hold (the lower rate).

Billing History itemizes each segment for every call; the builder's all-in
rate reflects live conversation time.

## Call transfers

When your agent hands a call off with a cold transfer, your carrier takes the
call over and ThunderPhone's charges stop when the agent leaves. When
ThunderPhone keeps the transferred call connected itself, that connected time
bills at **{/* rate:transfer-bridge */}1¢/min{/* /rate */}**, plus the ThunderPhone number rate when the
call uses a ThunderPhone number. This covers a warm transfer after the agent
drops off, and a cold transfer your carrier refused. See
[Call transfers](/guides/call-transfers).

For high-volume **outbound** use cases with long hold times, voicemail, or
call screeners, further reduced rates are available under an enterprise
agreement. [Reach out](mailto:sales@thunderphone.com) to learn more.

## Simulations and testing

An AI simulation runs two sides: your selected agent and a simulated caller.
The charge is itemized from both sides rather than applying a blanket “2×”
multiplier. The launch dialog shows an estimate for up to **10 minutes** and
requires explicit approval; shorter simulations cost less.

- The simulated caller uses the Spark rate.
- Your agent uses its actual tier, voice/language, and prompt additions.
- A phone-number simulation also includes the applicable telephony leg.

Saved scenario suites and validation runs display their own estimate before or
during execution.

## Phone numbers

{/* rate:phone-numbers */}

| Number type | ThunderPhone charge |
| --- | --- |
| **ThunderPhone number** | **$1/month** plus **1¢/min** on calls using it. An organization can hold 25 by default; request a higher limit from the Phone numbers page. |
| **Imported VoIP number** | No ThunderPhone import or monthly-number charge. Your VoIP provider continues to bill its own number and telephony usage. |

{/* /rate */}

Provisioning or releasing a ThunderPhone number starts or stops its monthly billing.
Deleting an imported number disconnects it from ThunderPhone but does not
cancel it with the provider.

## One-time charges

- **Generated voice sample:** **3¢** for a new voice/text/language sample;
  identical cached samples are free.
- Other billed operations present an estimate or confirmation before charging
  the organization balance.

## Balance, top-ups, and spending controls

Add a payment method and at least **$3.00** to begin making real calls. Funds do
not expire. Manual top-ups add a chosen amount immediately.

Optional auto top-up has three controls:

- Balance threshold that triggers the refill.
- Refill amount, at least $1.
- Optional monthly spending limit. When reached, new calls and usage pause
  until the next month or a higher limit; alerts are sent at 80% and 100%.

The monthly limit remains effective even if auto top-up is later disabled.
See [Billing and top-ups](/guides/billing-and-topups) and the
[Billing API](/api-reference/billing) for account and transaction operations.