diff --git a/esphome/components/sun/text_sensor/sun_text_sensor.h b/esphome/components/sun/text_sensor/sun_text_sensor.h
index 9345a32223..c3b60ffd65 100644
--- a/esphome/components/sun/text_sensor/sun_text_sensor.h
+++ b/esphome/components/sun/text_sensor/sun_text_sensor.h
@@ -14,7 +14,9 @@ class SunTextSensor : public text_sensor::TextSensor, public PollingComponent {
   void set_parent(Sun *parent) { parent_ = parent; }
   void set_elevation(double elevation) { elevation_ = elevation; }
   void set_sunrise(bool sunrise) { sunrise_ = sunrise; }
-  void set_format(const std::string &format) { format_ = format; }
+  void set_format(const char *format) { this->format_ = format; }
+  /// Prevent accidental use of std::string which would dangle
+  void set_format(const std::string &format) = delete;
 
   void update() override {
     optional<ESPTime> res;
@@ -29,14 +31,14 @@ class SunTextSensor : public text_sensor::TextSensor, public PollingComponent {
     }
 
     char buf[ESPTime::STRFTIME_BUFFER_SIZE];
-    size_t len = res->strftime_to(buf, this->format_.c_str());
+    size_t len = res->strftime_to(buf, this->format_);
     this->publish_state(buf, len);
   }
 
   void dump_config() override;
 
  protected:
-  std::string format_{};
+  const char *format_{nullptr};
   Sun *parent_;
   double elevation_;
   bool sunrise_;