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The strongest privacy design for a DIY smart speaker is an end-to-end local pipeline: the satellite sends microphone audio to a computer in your home, local speech recognition turns it into text, Home Assistant interprets the command, and a local text-to-speech engine speaks the reply. Then protect the satellite’s network interfaces, provide a real microphone cutoff, and audit every integration that could still contact an external service.
A local Home Assistant installation does not automatically make every voice feature local. Privacy depends on the complete path from wake word to logs, including optional accounts, cloud assistants, large-language-model integrations, and remote text-to-speech services.
Define what “private” means for a voice assistant
Voice privacy is a data-path question, not a product-label question. A useful audit follows each stage of one interaction:
- Wake-word detection: Determine whether the hot-word model runs on the satellite or whether audio is sent elsewhere first.
- Microphone capture: Identify when the microphone is powered and what event starts streaming.
- Speech-to-text (STT): Check which engine receives the audio and where it runs.
- Intent and conversation handling: Verify whether Home Assistant processes the text locally or forwards it to an account, cloud assistant, or hosted language model.
- Text-to-speech (TTS): Confirm whether the response is synthesized on your host or by an external service.
- Storage and logs: Review retained transcripts, debug logs, recordings, backups, and integrations that may copy command data.
Home Assistant’s privacy FAQ describes the platform boundary this way: it runs on your own hardware, stores data locally, and can communicate directly with supported devices over your local network. Optional cloud services perform only the functions you enable. That means you must inspect each enabled component rather than treating “Home Assistant” as a guarantee that every byte stays home.
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Use a fully local Assist pipeline
Home Assistant’s fully local voice guide describes the desired result: a microphone hears you, a local STT engine converts speech to text, Home Assistant determines the action, and a local TTS engine speaks the answer. In that configuration, voice data is not sent to external servers for processing. The following choices implement that design.
Choose local speech-to-text for your workload
| Engine | Best fit | Documented host examples | Trade-offs |
|---|---|---|---|
| Speech-to-Phrase | Predefined home-control commands | Home Assistant’s guide reports under one second on Home Assistant Green or a Raspberry Pi 4 | Close-ended recognition; it handles a subset of Assist commands and is less suitable for free-form dictation |
| Whisper | Open-ended speech and broader transcription | The guide reports around eight seconds to process an incoming command on a Raspberry Pi 4 and under one second on an Intel NUC | Needs substantially more processing power; language support and accuracy vary by model, language, and hardware |
Those times are examples published in Home Assistant documentation, not independent benchmarks. Your microphone, model, language, storage, concurrent automations, and thermal limits can change latency. Test the actual host with the phrases your household uses before deciding that a delay is acceptable.
Speech-to-Phrase is usually the practical privacy choice for lights, switches, scenes, timers, and other tightly defined controls. Whisper is the better fit when users expect open-ended transcription or commands outside that vocabulary, provided the host can process it promptly. Local processing does not eliminate recognition errors; it only keeps the audio-processing step on hardware you control.
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Keep intent handling local
After STT produces text, Assist still has to interpret it. Use Home Assistant’s local conversation and intent handling for the commands you want to keep inside the home. Review every conversation agent, custom integration, and linked account. A cloud conversation agent or a hosted language-model integration changes the privacy boundary even if STT and TTS are local.
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Use local text-to-speech
Piper is Home Assistant’s documented local TTS option. With Piper running on your own host, the response text and generated audio remain inside the local pipeline. If you select a remote TTS provider for a particular voice or language, treat that provider as an external recipient and document exactly which commands can reach it.
Understand the ESPHome satellite data path
In ESPHome’s documented voice-assistant flow, the satellite’s microphone streams audio to Home Assistant for Assist processing. A configured speaker on the satellite can play the response. The ESP device is therefore an audio endpoint; the Home Assistant host performs the speech and conversation work unless you have explicitly configured another component.
Inspect your own YAML and device behavior rather than assuming a default. Confirm:
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- whether wake-word detection is configured and where it runs;
- what event starts and stops listening;
- which speaker or media output receives TTS audio;
- which Assist pipeline and conversation agent Home Assistant uses; and
- whether any automation, add-on, or integration forwards transcripts or audio outside the network.
ESPHome warns that voice and audio components consume significant RAM and CPU. Combining them with too many other components can cause instability or crashes. Reduce unrelated sensors, displays, effects, and logging if the satellite resets while listening, and verify that the board’s audio interfaces and memory are adequate before adding features.
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Add a trustworthy microphone cutoff
A software mute icon is useful, but a physical cutoff provides a clearer guarantee: when muted, the microphone has no power path to deliver audio. Home Assistant’s Voice Preview Edition documentation describes a switch that physically cuts power to its microphones. That is a documented property of that device, not a universal feature of DIY hardware.
For a custom satellite, choose a board or circuit with a microphone-power switch you can verify electrically. Check that:
- the switch interrupts microphone power rather than only changing a software state;
- the indicator visibly shows the mute state;
- firmware cannot silently re-enable the microphone while the switch is off; and
- the cutoff covers every microphone in the enclosure, including any secondary or beam-forming element.
If your design cannot provide a trustworthy hardware cutoff, state that limitation plainly and use a removable microphone, a physical disconnect, or unplugging the satellite when private conversations occur.
Secure ESPHome communications
Privacy controls are ineffective if another device on the LAN can read sensor data, invoke entities, or replace firmware. Apply ESPHome’s security recommendations to every satellite.
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Encrypt the native API
- Enable ESPHome native API encryption for the device.
- Generate a unique encryption key for each satellite; never reuse one key across the fleet.
- Store the key in your secret-management mechanism, not in a public repository, shared screenshot, or exported configuration.
- Revoke and replace the key if the device, backup, or repository containing it may have been exposed.
ESPHome warns that without API encryption, people on the local network can read device sensor data and control entities. Encryption protects the API channel; it does not make an untrusted network safe by itself.
Protect or remove the ESPHome web server
Disable the ESPHome web server unless you need its browser interface. If it is required, set a long, unique password and restrict access to a trusted network. ESPHome documents that its web server lacks CSRF protection by design, so authentication and network isolation are important defenses. Do not expose the interface directly to the internet.
Encrypt over-the-air updates
Enable OTA encryption. ESPHome notes that OTA images contain Wi-Fi credentials and the API encryption key; transferring them without encryption can expose those secrets and permit malicious firmware uploads. Limit who can initiate updates, keep a known-good firmware image, and test recovery before changing the device remotely.
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The simplest arrangement for most households is to put the ESPHome satellite and Home Assistant on the same trusted network. ESPHome notes that mDNS discovery does not cross VLANs, so a segmented design can require manual addresses, firewall rules, and additional troubleshooting. Segmentation can still reduce blast radius for advanced users, but it is not a plug-and-play privacy switch.
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If you use a separate IoT VLAN, explicitly allow only the traffic the satellite needs to Home Assistant, DNS, and time synchronization. Block unsolicited access from the IoT network to laptops, phones, cameras, and administrative interfaces. Permit management traffic only from an administrator network. Test discovery and API connectivity after each firewall change; do not solve a discovery problem by opening the entire network.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Implement the local, hardened design step by step
- Map the current path. Write down the satellite, wake-word component, STT engine, conversation agent, TTS engine, storage locations, and every account or integration involved.
- Select the local STT engine. Start with Speech-to-Phrase for focused home control. Choose Whisper when open-ended transcription justifies the additional host resources.
- Install and select local TTS. Configure Piper and select it as the response engine for the Assist pipeline you intend to use.
- Remove unintended cloud dependencies. Disable cloud conversation agents, remote STT/TTS providers, and integrations that are not necessary for the commands you want to keep private.
- Configure the ESPHome satellite. Set the microphone, speaker, wake-word behavior, and listening-state automations. Keep the component set small enough for the board’s RAM and CPU.
- Add hardware mute. Verify that the physical switch removes microphone power and that its indicator is unambiguous.
- Enable API encryption. Create and protect a unique key for the device, then reconnect it to Home Assistant using the encrypted API.
- Harden web and OTA access. Disable the web server when unused; otherwise authenticate it. Enable OTA encryption and restrict who can update firmware.
- Apply network controls. Keep the satellite and Home Assistant on a trusted network or create narrowly scoped firewall rules for a segmented network.
- Test with packet and log reviews. Issue representative commands, inspect Home Assistant and ESPHome logs, and review router or firewall records for unexpected external connections.
Verify that privacy survives real use
Test each listening state
Observe the satellite while it is idle, after the wake word, during a failed recognition, and after a timeout. Confirm that audio streaming begins only under the configured trigger and stops when the listening event ends. If your design uses continuous listening, document that choice rather than describing it as wake-word-only.
Check every language you plan to use
Local engine support and recognition quality differ by language. Test accented speech, names of devices, background noise, and simultaneous speakers. A model that is fast in one language may be slower or less accurate in another.
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Review Assist history, debug logging, backups, and database retention. Disable verbose audio or transcript logging unless you need it for troubleshooting, and protect backups with the same care as the live host. Local storage limits exposure to third parties; it does not prevent another person with access to the host or backup from reading the data.
Repeat after updates
Updating Home Assistant, ESPHome, models, or integrations can change defaults and resource use. Re-check the current documentation, pipeline selection, API encryption, web-server status, OTA settings, and outbound network behavior after significant updates.
Compare the main privacy trade-offs
| Design choice | Privacy boundary | Command coverage and language | Latency and resources | Maintenance burden | Physical control |
|---|---|---|---|---|---|
| DIY ESPHome satellite with fully local Assist | Audio, STT, intent handling, and TTS can stay on the home network when each component is local | Depends on the selected local engines and language models | Depends on the Home Assistant host; Speech-to-Phrase is aimed at speed, while Whisper needs more compute | You maintain wiring, firmware, keys, updates, and network rules | You must verify and install a real microphone cutoff |
| DIY satellite with one or more cloud components | Audio, transcripts, or response text may leave home according to the selected service | May offer broader language or conversation features | Depends on internet connectivity and remote service response time | Fewer local compute demands, but account and provider settings require review | Hardware mute remains your responsibility |
| Home Assistant Voice Preview Edition | Supports local or cloud processing according to the configured pipeline | Determined by the selected Assist engines | Determined by the host and engines | Less custom hardware work than a self-built satellite | Documented switch physically cuts power to its microphones |
The key comparison is not DIY versus ready-made. It is whether you can verify every processing stage, secure the network connection, and physically disable the microphones when desired.
Troubleshoot common privacy failures
| Symptom | Likely cause | Corrective action |
|---|---|---|
| Commands work, but audio appears in an external service log | A cloud STT, conversation, TTS, or language-model component is selected | Inspect the active Assist pipeline and integration settings; replace that component with a local option or accept and document the external data path |
| Whisper responses take several seconds on a small host | The host lacks processing capacity for the chosen model | Use Speech-to-Phrase for supported home-control commands, move processing to a more capable host, or accept the documented latency trade-off |
| The satellite crashes when voice features are enabled | Audio components and other ESPHome features exceed available RAM or CPU | Remove nonessential components, reduce logging, and verify board and audio-interface requirements |
| Home Assistant cannot discover the satellite after VLAN changes | mDNS discovery does not cross VLANs | Keep both devices on the same trusted network or configure explicit addressing and narrowly scoped firewall rules |
| Another LAN device can control the satellite | Native API encryption is disabled or keys are shared | Enable encryption, assign a unique key, rotate exposed keys, and review network access |
| A mute button changes an icon but the microphone still has power | The control is software-only | Add a verified hardware cutoff or disconnect the microphone when private conversations occur |
| OTA credentials appear in a captured update | OTA transfer is unencrypted | Enable OTA encryption and limit update access to a trusted administrator network |
Maintain the privacy boundary over time
- Monthly: Review the active Assist pipeline, conversation agent, STT/TTS selections, and enabled integrations.
- After hardware changes: Confirm microphone power switching, speaker routing, wake-word behavior, and board resource headroom.
- After firmware changes: Verify API encryption, OTA encryption, web-server status, and secret handling.
- After network changes: Test discovery, firewall rules, and outbound connections from the satellite.
- Before enabling a new feature: Identify whether it needs an account or sends audio, transcripts, or response text to an external server.
- During incident response: Cut microphone power, disconnect the satellite, rotate API credentials, inspect logs and router records, and reinstall known-good firmware if compromise is suspected.
The practical privacy standard
A DIY smart speaker is meaningfully private when you can trace one command from microphone to speaker, show that each processing stage is local, prevent unauthorized LAN control, and physically remove microphone power on demand. Home Assistant’s local pipeline and ESPHome’s encrypted API provide the software foundation, but the builder must still choose the engines, secure the network, protect secrets, and verify the actual hardware mute circuit. Treat every cloud integration as a deliberate exception rather than an invisible default.
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