diff --git a/src/driver/drv_pwrCal.c b/src/driver/drv_pwrCal.c
index 82a7fe951..0aebd8f91 100644
--- a/src/driver/drv_pwrCal.c
+++ b/src/driver/drv_pwrCal.c
@@ -30,6 +30,11 @@ static commandResult_t Calibrate(const char *cmd, const char *args, float raw,
                      CMD_GetResultString(CMD_RES_BAD_ARGUMENT));
         return CMD_RES_BAD_ARGUMENT;
     }
+#define VERY_SMALL_VAL 0.001f
+	if (raw > -VERY_SMALL_VAL && raw < VERY_SMALL_VAL) {
+		ADDLOG_ERROR(LOG_FEATURE_ENERGYMETER, "Calibration incorrect - connect load first.");
+	}
+
 
     *cal = (cal_type == PWR_CAL_MULTIPLY ? real / raw : raw / real);
     CFG_SetPowerMeasurementCalibrationFloat(cfg_index, *cal);