diff --git a/controllers/autoscaling.go b/controllers/autoscaling.go
index 0035ca9c87..4e9edd5535 100644
--- a/controllers/autoscaling.go
+++ b/controllers/autoscaling.go
@@ -34,7 +34,7 @@ func getValueAvailableAt(now time.Time, from, to *time.Time, reservedValue int)
 	return &reservedValue
 }
 
-func (r *HorizontalRunnerAutoscalerReconciler) getDesiredReplicasFromCache(hra v1alpha1.HorizontalRunnerAutoscaler) *int {
+func (r *HorizontalRunnerAutoscalerReconciler) fetchSuggestedReplicasFromCache(hra v1alpha1.HorizontalRunnerAutoscaler) *int {
 	var entry *v1alpha1.CacheEntry
 
 	for i := range hra.Status.CacheEntries {
@@ -63,7 +63,7 @@ func (r *HorizontalRunnerAutoscalerReconciler) getDesiredReplicasFromCache(hra v
 	return nil
 }
 
-func (r *HorizontalRunnerAutoscalerReconciler) determineDesiredReplicas(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
+func (r *HorizontalRunnerAutoscalerReconciler) suggestDesiredReplicas(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
 	if hra.Spec.MinReplicas == nil {
 		return nil, fmt.Errorf("horizontalrunnerautoscaler %s/%s is missing minReplicas", hra.Namespace, hra.Name)
 	} else if hra.Spec.MaxReplicas == nil {
@@ -73,20 +73,20 @@ func (r *HorizontalRunnerAutoscalerReconciler) determineDesiredReplicas(rd v1alp
 	metrics := hra.Spec.Metrics
 	if len(metrics) == 0 {
 		if len(hra.Spec.ScaleUpTriggers) == 0 {
-			return r.calculateReplicasByQueuedAndInProgressWorkflowRuns(rd, hra)
+			return r.suggestReplicasByQueuedAndInProgressWorkflowRuns(rd, hra)
 		}
 
-		return hra.Spec.MinReplicas, nil
+		return nil, nil
 	} else if metrics[0].Type == v1alpha1.AutoscalingMetricTypeTotalNumberOfQueuedAndInProgressWorkflowRuns {
-		return r.calculateReplicasByQueuedAndInProgressWorkflowRuns(rd, hra)
+		return r.suggestReplicasByQueuedAndInProgressWorkflowRuns(rd, hra)
 	} else if metrics[0].Type == v1alpha1.AutoscalingMetricTypePercentageRunnersBusy {
-		return r.calculateReplicasByPercentageRunnersBusy(rd, hra)
+		return r.suggestReplicasByPercentageRunnersBusy(rd, hra)
 	} else {
 		return nil, fmt.Errorf("validting autoscaling metrics: unsupported metric type %q", metrics[0].Type)
 	}
 }
 
-func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByQueuedAndInProgressWorkflowRuns(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
+func (r *HorizontalRunnerAutoscalerReconciler) suggestReplicasByQueuedAndInProgressWorkflowRuns(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
 
 	var repos [][]string
 	metrics := hra.Spec.Metrics
@@ -101,7 +101,7 @@ func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByQueuedAndInPro
 		// we assume that the desired replicas should always be `minReplicas + capacityReservedThroughWebhook`.
 		// See https://github.com/summerwind/actions-runner-controller/issues/377#issuecomment-793372693
 		if len(metrics) == 0 {
-			return hra.Spec.MinReplicas, nil
+			return nil, nil
 		}
 
 		if len(metrics[0].RepositoryNames) == 0 {
@@ -178,28 +178,10 @@ func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByQueuedAndInPro
 		}
 	}
 
-	minReplicas := *hra.Spec.MinReplicas
-	maxReplicas := *hra.Spec.MaxReplicas
 	necessaryReplicas := queued + inProgress
 
-	var desiredReplicas int
-
-	if necessaryReplicas < minReplicas {
-		desiredReplicas = minReplicas
-	} else if necessaryReplicas > maxReplicas {
-		desiredReplicas = maxReplicas
-	} else {
-		desiredReplicas = necessaryReplicas
-	}
-
-	rd.Status.Replicas = &desiredReplicas
-	replicas := desiredReplicas
-
 	r.Log.V(1).Info(
-		"Calculated desired replicas",
-		"computed_replicas_desired", desiredReplicas,
-		"spec_replicas_min", minReplicas,
-		"spec_replicas_max", maxReplicas,
+		fmt.Sprintf("Suggested desired replicas of %d by TotalNumberOfQueuedAndInProgressWorkflowRuns", necessaryReplicas),
 		"workflow_runs_completed", completed,
 		"workflow_runs_in_progress", inProgress,
 		"workflow_runs_queued", queued,
@@ -209,13 +191,11 @@ func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByQueuedAndInPro
 		"horizontal_runner_autoscaler", hra.Name,
 	)
 
-	return &replicas, nil
+	return &necessaryReplicas, nil
 }
 
-func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByPercentageRunnersBusy(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
+func (r *HorizontalRunnerAutoscalerReconciler) suggestReplicasByPercentageRunnersBusy(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
 	ctx := context.Background()
-	minReplicas := *hra.Spec.MinReplicas
-	maxReplicas := *hra.Spec.MaxReplicas
 	metrics := hra.Spec.Metrics[0]
 	scaleUpThreshold := defaultScaleUpThreshold
 	scaleDownThreshold := defaultScaleDownThreshold
@@ -363,21 +343,13 @@ func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByPercentageRunn
 		desiredReplicas = *rd.Spec.Replicas
 	}
 
-	if desiredReplicas < minReplicas {
-		desiredReplicas = minReplicas
-	} else if desiredReplicas > maxReplicas {
-		desiredReplicas = maxReplicas
-	}
-
 	// NOTES for operators:
 	//
 	// - num_runners can be as twice as large as replicas_desired_before while
 	//   the runnerdeployment controller is replacing RunnerReplicaSet for runner update.
 
 	r.Log.V(1).Info(
-		"Calculated desired replicas",
-		"replicas_min", minReplicas,
-		"replicas_max", maxReplicas,
+		fmt.Sprintf("Suggested desired replicas of %d by PercentageRunnersBusy", desiredReplicas),
 		"replicas_desired_before", desiredReplicasBefore,
 		"replicas_desired", desiredReplicas,
 		"num_runners", numRunners,
@@ -391,8 +363,5 @@ func (r *HorizontalRunnerAutoscalerReconciler) calculateReplicasByPercentageRunn
 		"repository", repository,
 	)
 
-	rd.Status.Replicas = &desiredReplicas
-	replicas := desiredReplicas
-
-	return &replicas, nil
+	return &desiredReplicas, nil
 }
diff --git a/controllers/autoscaling_test.go b/controllers/autoscaling_test.go
index 50d458fa97..01921d9483 100644
--- a/controllers/autoscaling_test.go
+++ b/controllers/autoscaling_test.go
@@ -224,7 +224,7 @@ func TestDetermineDesiredReplicas_RepositoryRunner(t *testing.T) {
 				},
 			}
 
-			got, err := h.computeReplicas(rd, hra)
+			got, _, _, err := h.computeReplicasWithCache(log, metav1Now.Time, rd, hra)
 			if err != nil {
 				if tc.err == "" {
 					t.Fatalf("unexpected error: expected none, got %v", err)
@@ -234,12 +234,8 @@ func TestDetermineDesiredReplicas_RepositoryRunner(t *testing.T) {
 				return
 			}
 
-			if got == nil {
-				t.Fatalf("unexpected value of rs.Spec.Replicas: nil")
-			}
-
-			if *got != tc.want {
-				t.Errorf("%d: incorrect desired replicas: want %d, got %d", i, tc.want, *got)
+			if got != tc.want {
+				t.Errorf("%d: incorrect desired replicas: want %d, got %d", i, tc.want, got)
 			}
 		})
 	}
@@ -424,6 +420,8 @@ func TestDetermineDesiredReplicas_OrganizationalRunner(t *testing.T) {
 		_ = v1alpha1.AddToScheme(scheme)
 
 		t.Run(fmt.Sprintf("case %d", i), func(t *testing.T) {
+			t.Helper()
+
 			server := fake.NewServer(
 				fake.WithListRepositoryWorkflowRunsResponse(200, tc.workflowRuns, tc.workflowRuns_queued, tc.workflowRuns_in_progress),
 				fake.WithListWorkflowJobsResponse(200, tc.workflowJobs),
@@ -485,7 +483,7 @@ func TestDetermineDesiredReplicas_OrganizationalRunner(t *testing.T) {
 				},
 			}
 
-			got, err := h.computeReplicas(rd, hra)
+			got, _, _, err := h.computeReplicasWithCache(log, metav1Now.Time, rd, hra)
 			if err != nil {
 				if tc.err == "" {
 					t.Fatalf("unexpected error: expected none, got %v", err)
@@ -495,12 +493,8 @@ func TestDetermineDesiredReplicas_OrganizationalRunner(t *testing.T) {
 				return
 			}
 
-			if got == nil {
-				t.Fatalf("unexpected value of rs.Spec.Replicas: nil, wanted %v", tc.want)
-			}
-
-			if *got != tc.want {
-				t.Errorf("%d: incorrect desired replicas: want %d, got %d", i, tc.want, *got)
+			if got != tc.want {
+				t.Errorf("%d: incorrect desired replicas: want %d, got %d", i, tc.want, got)
 			}
 		})
 	}
diff --git a/controllers/horizontalrunnerautoscaler_controller.go b/controllers/horizontalrunnerautoscaler_controller.go
index ce2959c0a3..a64b83b13f 100644
--- a/controllers/horizontalrunnerautoscaler_controller.go
+++ b/controllers/horizontalrunnerautoscaler_controller.go
@@ -19,6 +19,7 @@ package controllers
 import (
 	"context"
 	"fmt"
+	corev1 "k8s.io/api/core/v1"
 	"time"
 
 	"github.com/summerwind/actions-runner-controller/github"
@@ -30,7 +31,6 @@ import (
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 
-	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 
 	"github.com/summerwind/actions-runner-controller/api/v1alpha1"
@@ -52,6 +52,8 @@ type HorizontalRunnerAutoscalerReconciler struct {
 	Name          string
 }
 
+const defaultReplicas = 1
+
 // +kubebuilder:rbac:groups=actions.summerwind.dev,resources=runnerdeployments,verbs=get;list;watch;update;patch
 // +kubebuilder:rbac:groups=actions.summerwind.dev,resources=horizontalrunnerautoscalers,verbs=get;list;watch;create;update;patch;delete
 // +kubebuilder:rbac:groups=actions.summerwind.dev,resources=horizontalrunnerautoscalers/finalizers,verbs=get;list;watch;create;update;patch;delete
@@ -83,41 +85,18 @@ func (r *HorizontalRunnerAutoscalerReconciler) Reconcile(req ctrl.Request) (ctrl
 		return ctrl.Result{}, nil
 	}
 
-	var replicas *int
-
-	replicasFromCache := r.getDesiredReplicasFromCache(hra)
-
-	if replicasFromCache != nil {
-		replicas = replicasFromCache
-	} else {
-		var err error
+	now := time.Now()
 
-		replicas, err = r.computeReplicas(rd, hra)
-		if err != nil {
-			r.Recorder.Event(&hra, corev1.EventTypeNormal, "RunnerAutoscalingFailure", err.Error())
+	newDesiredReplicas, computedReplicas, computedReplicasFromCache, err := r.computeReplicasWithCache(log, now, rd, hra)
+	if err != nil {
+		r.Recorder.Event(&hra, corev1.EventTypeNormal, "RunnerAutoscalingFailure", err.Error())
 
-			log.Error(err, "Could not compute replicas")
+		log.Error(err, "Could not compute replicas")
 
-			return ctrl.Result{}, err
-		}
+		return ctrl.Result{}, err
 	}
 
-	const defaultReplicas = 1
-
 	currentDesiredReplicas := getIntOrDefault(rd.Spec.Replicas, defaultReplicas)
-	newDesiredReplicas := getIntOrDefault(replicas, defaultReplicas)
-
-	now := time.Now()
-
-	for _, reservation := range hra.Spec.CapacityReservations {
-		if reservation.ExpirationTime.Time.After(now) {
-			newDesiredReplicas += reservation.Replicas
-		}
-	}
-
-	if hra.Spec.MaxReplicas != nil && *hra.Spec.MaxReplicas < newDesiredReplicas {
-		newDesiredReplicas = *hra.Spec.MaxReplicas
-	}
 
 	// Please add more conditions that we can in-place update the newest runnerreplicaset without disruption
 	if currentDesiredReplicas != newDesiredReplicas {
@@ -143,7 +122,7 @@ func (r *HorizontalRunnerAutoscalerReconciler) Reconcile(req ctrl.Request) (ctrl
 		updated.Status.DesiredReplicas = &newDesiredReplicas
 	}
 
-	if replicasFromCache == nil {
+	if computedReplicasFromCache == nil {
 		if updated == nil {
 			updated = hra.DeepCopy()
 		}
@@ -160,7 +139,7 @@ func (r *HorizontalRunnerAutoscalerReconciler) Reconcile(req ctrl.Request) (ctrl
 
 		updated.Status.CacheEntries = append(cacheEntries, v1alpha1.CacheEntry{
 			Key:            v1alpha1.CacheEntryKeyDesiredReplicas,
-			Value:          *replicas,
+			Value:          computedReplicas,
 			ExpirationTime: metav1.Time{Time: time.Now().Add(cacheDuration)},
 		})
 	}
@@ -200,14 +179,59 @@ func (r *HorizontalRunnerAutoscalerReconciler) SetupWithManager(mgr ctrl.Manager
 		Complete(r)
 }
 
-func (r *HorizontalRunnerAutoscalerReconciler) computeReplicas(rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (*int, error) {
-	var computedReplicas *int
+func (r *HorizontalRunnerAutoscalerReconciler) computeReplicasWithCache(log logr.Logger, now time.Time, rd v1alpha1.RunnerDeployment, hra v1alpha1.HorizontalRunnerAutoscaler) (int, int, *int, error) {
+	minReplicas := defaultReplicas
+	if hra.Spec.MinReplicas != nil && *hra.Spec.MinReplicas > 0 {
+		minReplicas = *hra.Spec.MinReplicas
+	}
 
-	replicas, err := r.determineDesiredReplicas(rd, hra)
-	if err != nil {
-		return nil, err
+	var suggestedReplicas int
+
+	suggestedReplicasFromCache := r.fetchSuggestedReplicasFromCache(hra)
+
+	var cached *int
+
+	if suggestedReplicasFromCache != nil {
+		cached = suggestedReplicasFromCache
+
+		if cached == nil {
+			suggestedReplicas = minReplicas
+		} else {
+			suggestedReplicas = *cached
+		}
+	} else {
+		v, err := r.suggestDesiredReplicas(rd, hra)
+		if err != nil {
+			return 0, 0, nil, err
+		}
+
+		if v == nil {
+			suggestedReplicas = minReplicas
+		} else {
+			suggestedReplicas = *v
+		}
+	}
+
+	var reserved int
+
+	for _, reservation := range hra.Spec.CapacityReservations {
+		if reservation.ExpirationTime.Time.After(now) {
+			reserved += reservation.Replicas
+		}
+	}
+
+	newDesiredReplicas := suggestedReplicas + reserved
+
+	if newDesiredReplicas < minReplicas {
+		newDesiredReplicas = minReplicas
+	} else if hra.Spec.MaxReplicas != nil && newDesiredReplicas > *hra.Spec.MaxReplicas {
+		newDesiredReplicas = *hra.Spec.MaxReplicas
 	}
 
+	//
+	// Delay scaling-down for ScaleDownDelaySecondsAfterScaleUp or DefaultScaleDownDelay
+	//
+
 	var scaleDownDelay time.Duration
 
 	if hra.Spec.ScaleDownDelaySecondsAfterScaleUp != nil {
@@ -216,17 +240,50 @@ func (r *HorizontalRunnerAutoscalerReconciler) computeReplicas(rd v1alpha1.Runne
 		scaleDownDelay = DefaultScaleDownDelay
 	}
 
-	now := time.Now()
+	var scaleDownDelayUntil *time.Time
 
 	if hra.Status.DesiredReplicas == nil ||
-		*hra.Status.DesiredReplicas < *replicas ||
-		hra.Status.LastSuccessfulScaleOutTime == nil ||
-		hra.Status.LastSuccessfulScaleOutTime.Add(scaleDownDelay).Before(now) {
+		*hra.Status.DesiredReplicas < newDesiredReplicas ||
+		hra.Status.LastSuccessfulScaleOutTime == nil {
 
-		computedReplicas = replicas
+	} else if hra.Status.LastSuccessfulScaleOutTime != nil {
+		t := hra.Status.LastSuccessfulScaleOutTime.Add(scaleDownDelay)
+
+		// ScaleDownDelay is not passed
+		if t.After(now) {
+			scaleDownDelayUntil = &t
+			newDesiredReplicas = *hra.Status.DesiredReplicas
+		}
 	} else {
-		computedReplicas = hra.Status.DesiredReplicas
+		newDesiredReplicas = *hra.Status.DesiredReplicas
+	}
+
+	//
+	// Logs various numbers for monitoring and debugging purpose
+	//
+
+	kvs := []interface{}{
+		"suggested", suggestedReplicas,
+		"reserved", reserved,
+		"min", minReplicas,
 	}
 
-	return computedReplicas, nil
+	if cached != nil {
+		kvs = append(kvs, "cached", *cached)
+	}
+
+	if scaleDownDelayUntil != nil {
+		kvs = append(kvs, "last_scale_up_time", *hra.Status.LastSuccessfulScaleOutTime)
+		kvs = append(kvs, "scale_down_delay_until", scaleDownDelayUntil)
+	}
+
+	if maxReplicas := hra.Spec.MaxReplicas; maxReplicas != nil {
+		kvs = append(kvs, "max", *maxReplicas)
+	}
+
+	log.V(1).Info(fmt.Sprintf("Calculated desired replicas of %d", newDesiredReplicas),
+		kvs...,
+	)
+
+	return newDesiredReplicas, suggestedReplicas, suggestedReplicasFromCache, nil
 }