diff --git a/README.md b/README.md
index 5695236..1de2feb 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,10 @@
 
 Static site generator for website to track BT InLink kiosks planning applications.
 
+## Environment variables
+
+$ export KIOSKS_SITEURL=https://kiosks.adrianshort.org
+
 [![Deploy to Netlify](https://www.netlify.com/img/deploy/button.svg)](https://app.netlify.com/start/deploy?repository=https://github.com/adrianshort/kiosks)
 
 ## How to build this site locally