diff --git a/services/baremetal-builder/default.nix b/services/baremetal-builder/default.nix
index 832ef9d..581a0e8 100644
--- a/services/baremetal-builder/default.nix
+++ b/services/baremetal-builder/default.nix
@@ -150,7 +150,11 @@ in
       script = "exec ${config.nix.package.out}/bin/nix-store --gc --store /mnt";
       serviceConfig.Type = "oneshot";
       serviceConfig.User = "builder";
-      startAt = "*-*-* 00/8:00:00";
+    };
+    systemd.timers.hydra-gc = {
+      timerConfig.OnStartupSec = "4h";
+      timerConfig.OnUnitActiveSec = "20h";
+      wantedBy = [ "timers.target" ];
     };
     systemd.timers.hydra-gc.timerConfig.Persistent = true;