diff --git a/Cargo.lock b/Cargo.lock
index e5b651a..9449ce1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -127,6 +127,9 @@ name = "bitflags"
 version = "2.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ed570934406eb16438a4e976b1b4500774099c13b8cb96eec99f620f05090ddf"
+dependencies = [
+ "serde",
+]
 
 [[package]]
 name = "block-buffer"
@@ -1102,6 +1105,18 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "ron"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b91f7eff05f748767f183df4320a63d6936e9c6107d97c9e6bdd9784f4289c94"
+dependencies = [
+ "base64",
+ "bitflags 2.4.2",
+ "serde",
+ "serde_derive",
+]
+
 [[package]]
 name = "rustc-demangle"
 version = "0.1.23"
@@ -1502,10 +1517,12 @@ dependencies = [
 
 [[package]]
 name = "tesla-common"
-version = "0.1.1"
+version = "0.2.0"
 dependencies = [
+ "ron",
  "serde",
  "teslatte",
+ "thiserror",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index 350306d..797247f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "tesla-common"
-version = "0.1.1"
+version = "0.2.0"
 edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
@@ -8,3 +8,5 @@ edition = "2021"
 [dependencies]
 serde = { version = "1.0", features = ["derive"] }
 teslatte = { git = "https://git.alexjanka.com/alex/teslatte" }
+ron = "0.8"
+thiserror = "1.0"
diff --git a/src/lib.rs b/src/lib.rs
index 1a0ba8a..70b7079 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,8 +1,25 @@
 use serde::{Deserialize, Serialize};
+use std::path::Path;
 use teslatte::auth::{AccessToken, RefreshToken};
+use thiserror::Error;
 
 #[derive(Serialize, Deserialize, Clone)]
 pub struct AuthInfo {
     pub access_token: AccessToken,
     pub refresh_token: Option<RefreshToken>,
 }
+
+impl AuthInfo {
+    pub fn save(&self, path: &Path) -> Result<(), SaveError> {
+        std::fs::write(path, ron::ser::to_string(self)?)?;
+        Ok(())
+    }
+}
+
+#[derive(Error, Debug)]
+pub enum SaveError {
+    #[error("stdio error")]
+    StdIo(#[from] std::io::Error),
+    #[error("ron")]
+    RonSpanned(#[from] ron::Error),
+}