diff --git a/main.c b/main.c
--- a/main.c
+++ b/main.c
@@ -92,6 +92,8 @@ int main(void)
     uint32_t last_thermostat = 0;
     int16_t ssr_output = 0; // Duty cycle of ssr, 0 to SSR_PERIOD 
 
+    uint8_t thermostat_plant_on = 0;
+
     // Main loop
     while(1)
     {
@@ -180,16 +182,20 @@ int main(void)
             temp_frac = status.temp > 0 ? temp_frac : temp_frac * -1;
             int32_t temp = (status.temp * 10) + temp_frac;
 
-            uint8_t plant_on = 0;
 
             // EMZ FIXME: This could be way simpler
-            if(set.val.plant_type == PLANT_HEATER && status.setpoint * 10 < temp)
-                plant_on = 1;
-            else if(set.val.plant_type == PLANT_COOLER && status.setpoint * 10 > temp)
-                plant_on = 1;
+            if(set.val.plant_type == PLANT_HEATER && status.setpoint * 10 < temp - set.val.hysteresis * 10)
+                thermostat_plant_on = 1;
+            else if(set.val.plant_type == PLANT_HEATER && status.setpoint * 10 > temp + set.val.hysteresis * 10)
+                thermostat_plant_on = 0;
+
+            if(set.val.plant_type == PLANT_COOLER && status.setpoint * 10 > temp + set.val.hysteresis * 10)
+                thermostat_plant_on = 1;
+            else if(set.val.plant_type == PLANT_COOLER && status.setpoint * 10 < temp - set.val.hysteresis * 10)
+                thermostat_plant_on = 0;
 
             // EMZ: TODO: Refactor to output_enabled or something
-            if(status.pid_enabled && plant_on)
+            if(status.pid_enabled && thermostat_plant_on)
             {
                 // EMZ TODO: functionalize this
             	// put ssr output on display