diff --git a/esphome/const.py b/esphome/const.py
index a21e18730f..b2437eca7e 100644
--- a/esphome/const.py
+++ b/esphome/const.py
@@ -1084,6 +1084,7 @@ UNIT_KILOWATT = "kW"
 UNIT_KILOWATT_HOURS = "kWh"
 UNIT_LITRE = "L"
 UNIT_LUX = "lx"
+UNIT_MEGAJOULE = "MJ"
 UNIT_METER = "m"
 UNIT_METER_PER_SECOND_SQUARED = "m/s²"
 UNIT_MICROAMP = "µA"