diff --git a/README.md b/README.md
index 06f76e5..1bec983 100644
--- a/README.md
+++ b/README.md
@@ -189,23 +189,45 @@ test -e config.toml || cp config.example.toml config.toml
 chmod 0644 config.toml
 ```
 
-The dynamic service user needs read access to this configuration. It contains setting
-values and environment variable names; keep credentials in the root-readable environment
-file below. Ensure the proxy serves the status endpoint rather than repository files.
+The `www-data` service user needs read access to this configuration. It contains
+setting values and environment variable names; keep credentials in the root-readable
+environment file below. Ensure the proxy serves the status endpoint rather than
+repository files.
 
-For systemd, set the archive to its writable state directory in this local config,
-retaining your other settings. The relative development setting `data/archive` points
-inside the checkout, which the hardened service cannot write:
+Keep the archive under `/var/www/html/solar-relay/data/archive`. The relative setting
+`data/archive` resolves to that location because paths are relative to `config.toml`.
+In the existing `[collector]` section, retain your other settings:
 
 ```toml
 [collector]
 source_id = "home-gen24"
-archive = "/var/lib/solar-relay/archive"
+archive = "data/archive"
 timezone = "Europe/Zurich"
 poll_interval_seconds = 300
 retention_days = 30
 ```
 
+The service uses the existing `www-data` account. If replacing an existing service,
+stop it before changing data ownership:
+
+```bash
+sudo systemctl stop solar-relay
+```
+
+Create the writable data directory once. The ownership change includes
+any existing archive files and leaves their contents intact:
+
+```bash
+sudo install -d -o www-data -g www-data -m 0700 \
+  /var/www/html/solar-relay/data /var/www/html/solar-relay/data/archive
+sudo chown -R www-data:www-data /var/www/html/solar-relay/data
+```
+
+The unit keeps the checkout read-only with `ProtectSystem=strict` and allows writes
+to `/var/www/html/solar-relay/data` through `ReadWritePaths`. The data directory must
+exist before starting the service. Do not run archive-writing CLI commands as another
+user; use `sudo -u www-data` to preserve ownership.
+
 Set `[upload].url` to the main website's `https://your-solar-host/index.php?a=relay`.
 Put `SOLAR_RELAY_TOKEN=your-shared-token` in `/etc/solar-relay/solar-relay.env` with
 permissions 0600, readable by root. Configure the same token and source ID on the
@@ -219,7 +241,6 @@ sudo systemctl daemon-reload
 sudo systemctl enable solar-relay
 ```
 
-systemd provides `/var/lib/solar-relay` to a dynamic, unprivileged service user.
 Recording/uploading remains separate from serving status. The first Gitea deployment
 installs the code/venv and starts the service through restart. After a manual installation,
 use `systemctl start solar-relay` when the code and venv are ready. Running
@@ -285,9 +306,10 @@ The workflow installs dependencies and runs tests in `.venv-ci`, checks the inst
 unit, serializes deployment with `flock`, syncs source, installs runtime dependencies
 inside `.venv`, restarts and checks the service, then probes the public HTTPS health
 endpoint with certificate verification. Runtime venv/configuration, `data/` and
-Parquet files are preserved. Recommended state under `/var/lib` and
-the credential environment file under `/etc` are outside the sync. The local
-`config.toml` is protected by the explicit rsync exclusion even when `--delete` is used.
+Parquet files are preserved. The archive under `data/archive` is protected by the
+`/data/` rsync exclusion, and the credential environment file under `/etc` is outside
+the sync. The local `config.toml` is protected by the explicit rsync exclusion even
+when `--delete` is used.
 Deployment never copies `config.example.toml` over your configuration.
 
 If the deployment directory is initially empty, enable the unit without `--now`; the
diff --git a/deploy/solar-relay.service b/deploy/solar-relay.service
index b55d6a1..c3dc96b 100644
--- a/deploy/solar-relay.service
+++ b/deploy/solar-relay.service
@@ -5,12 +5,11 @@ Wants=network-online.target
 
 [Service]
 Type=simple
-DynamicUser=yes
+User=www-data
+Group=www-data
 WorkingDirectory=/var/www/html/solar-relay
 ExecStart=/var/www/html/solar-relay/.venv/bin/python -m solar_relay --config /var/www/html/solar-relay/config.toml run
 EnvironmentFile=-/etc/solar-relay/solar-relay.env
-StateDirectory=solar-relay
-StateDirectoryMode=0700
 UMask=0077
 Restart=on-failure
 RestartSec=10
@@ -19,7 +18,7 @@ NoNewPrivileges=yes
 PrivateTmp=yes
 ProtectSystem=strict
 ProtectHome=yes
-ReadWritePaths=/var/lib/solar-relay
+ReadWritePaths=/var/www/html/solar-relay/data
 
 [Install]
 WantedBy=multi-user.target