diff --git a/esphome/components/water_heater/water_heater.cpp b/esphome/components/water_heater/water_heater.cpp
index 7266294d84..286addf7db 100644
--- a/esphome/components/water_heater/water_heater.cpp
+++ b/esphome/components/water_heater/water_heater.cpp
@@ -2,6 +2,7 @@
 #include "esphome/core/log.h"
 #include "esphome/core/application.h"
 #include "esphome/core/controller_registry.h"
+#include "esphome/core/progmem.h"
 
 #include <cmath>
 
@@ -22,23 +23,23 @@ WaterHeaterCall &WaterHeaterCall::set_mode(WaterHeaterMode mode) {
   return *this;
 }
 
-WaterHeaterCall &WaterHeaterCall::set_mode(const std::string &mode) {
-  if (str_equals_case_insensitive(mode, "OFF")) {
+WaterHeaterCall &WaterHeaterCall::set_mode(const char *mode) {
+  if (ESPHOME_strcasecmp_P(mode, ESPHOME_PSTR("OFF")) == 0) {
     this->set_mode(WATER_HEATER_MODE_OFF);
-  } else if (str_equals_case_insensitive(mode, "ECO")) {
+  } else if (ESPHOME_strcasecmp_P(mode, ESPHOME_PSTR("ECO")) == 0) {
     this->set_mode(WATER_HEATER_MODE_ECO);
-  } else if (str_equals_case_insensitive(mode, "ELECTRIC")) {
+  } else if (ESPHOME_strcasecmp_P(mode, ESPHOME_PSTR("ELECTRIC")) == 0) {
     this->set_mode(WATER_HEATER_MODE_ELECTRIC);
-  } else if (str_equals_case_insensitive(mode, "PERFORMANCE")) {
+  } else if (ESPHOME_strcasecmp_P(mode, ESPHOME_PSTR("PERFORMANCE")) == 0) {
     this->set_mode(WATER_HEATER_MODE_PERFORMANCE);
-  } else if (str_equals_case_insensitive(mode, "HIGH_DEMAND")) {
+  } else if (ESPHOME_strcasecmp_P(mode, ESPHOME_PSTR("HIGH_DEMAND")) == 0) {
     this->set_mode(WATER_HEATER_MODE_HIGH_DEMAND);
-  } else if (str_equals_case_insensitive(mode, "HEAT_PUMP")) {
+  } else if (ESPHOME_strcasecmp_P(mode, ESPHOME_PSTR("HEAT_PUMP")) == 0) {
     this->set_mode(WATER_HEATER_MODE_HEAT_PUMP);
-  } else if (str_equals_case_insensitive(mode, "GAS")) {
+  } else if (ESPHOME_strcasecmp_P(mode, ESPHOME_PSTR("GAS")) == 0) {
     this->set_mode(WATER_HEATER_MODE_GAS);
   } else {
-    ESP_LOGW(TAG, "'%s' - Unrecognized mode %s", this->parent_->get_name().c_str(), mode.c_str());
+    ESP_LOGW(TAG, "'%s' - Unrecognized mode %s", this->parent_->get_name().c_str(), mode);
   }
   return *this;
 }
diff --git a/esphome/components/water_heater/water_heater.h b/esphome/components/water_heater/water_heater.h
index 84fc46d208..7bd05ba7f5 100644
--- a/esphome/components/water_heater/water_heater.h
+++ b/esphome/components/water_heater/water_heater.h
@@ -75,7 +75,8 @@ class WaterHeaterCall {
   WaterHeaterCall(WaterHeater *parent);
 
   WaterHeaterCall &set_mode(WaterHeaterMode mode);
-  WaterHeaterCall &set_mode(const std::string &mode);
+  WaterHeaterCall &set_mode(const char *mode);
+  WaterHeaterCall &set_mode(const std::string &mode) { return this->set_mode(mode.c_str()); }
   WaterHeaterCall &set_target_temperature(float temperature);
   WaterHeaterCall &set_target_temperature_low(float temperature);
   WaterHeaterCall &set_target_temperature_high(float temperature);