diff --git a/esphome/components/api/proto.h b/esphome/components/api/proto.h
index 8d5e02943a9..e0a4e03189e 100644
--- a/esphome/components/api/proto.h
+++ b/esphome/components/api/proto.h
@@ -27,6 +27,8 @@ constexpr uint8_t WIRE_TYPE_MASK = 0b111;          // Mask to extract wire type
 
 // Reinterpret float bits as uint32_t without floating-point comparison.
 // Used by both encode_float() and calc_float() to ensure identical zero checks.
+// Uses union type-punning which is a GCC/Clang extension (not standard C++),
+// but bit_cast/memcpy don't optimize to a no-op on xtensa-gcc (ESP8266).
 inline uint32_t float_to_raw(float value) {
   union {
     float f;
@@ -456,14 +458,10 @@ class ProtoEncode {
   // is needed in the future, the necessary encoding/decoding functions must be added.
   static inline void encode_float(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id, float value,
                                   bool force = false) {
-    if (value == 0.0f && !force)
+    uint32_t raw = float_to_raw(value);
+    if (raw == 0 && !force)
       return;
-    union {
-      float value;
-      uint32_t raw;
-    } val{};
-    val.value = value;
-    encode_fixed32(pos PROTO_ENCODE_DEBUG_ARG, field_id, val.raw);
+    encode_fixed32(pos PROTO_ENCODE_DEBUG_ARG, field_id, raw);
   }
   static inline void encode_int32(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id, int32_t value,
                                   bool force = false) {