diff --git a/modules/nixos/homeassistant/services/esphome/default.nix b/modules/nixos/homeassistant/services/esphome/default.nix
index a62227b..20f944d 100644
--- a/modules/nixos/homeassistant/services/esphome/default.nix
+++ b/modules/nixos/homeassistant/services/esphome/default.nix
@@ -16,6 +16,10 @@ in
       ports = [ "6052:6052" ];
       volumes = [
         "/esphome:/config"
+        # Persist the PlatformIO core dir (penv, packages, platforms) so the
+        # pioarduino penv_setup.py dependency install only runs once rather
+        # than on every container restart.
+        "/esphome/.platformio:/root/.platformio"
       ];
       environment = {
         TZ = "America/Chicago";