diff --git a/.github/workflows/default.yml b/.github/workflows/default.yml
index 4fcd1b906a..045ebb20d7 100644
--- a/.github/workflows/default.yml
+++ b/.github/workflows/default.yml
@@ -149,6 +149,8 @@ jobs:
 
       - name: Lint
         uses: golangci/golangci-lint-action@v9
+        env:
+          GOEXPERIMENT: jsonv2
         with:
           version: latest
           args: --timeout 5m
diff --git a/Makefile b/Makefile
index 20159a6862..6ca6cc5880 100644
--- a/Makefile
+++ b/Makefile
@@ -46,23 +46,23 @@ ui::
 	npm run build
 
 assets::
-	go generate ./...
+	GOEXPERIMENT=jsonv2 go generate ./...
 
 docs::
-	go generate github.com/evcc-io/evcc/util/templates/...
+	GOEXPERIMENT=jsonv2 go generate github.com/evcc-io/evcc/util/templates/...
 
 lint::
-	golangci-lint run
-	go tool modernize -test -c 0 -stringsbuilder=false -omitzero=false ./...
+	GOEXPERIMENT=jsonv2 golangci-lint run
+	GOEXPERIMENT=jsonv2 go tool modernize -test -c 0 -stringsbuilder=false -omitzero=false ./...
 
 modernize:
-	go tool modernize -test -fix -stringsbuilder=false -omitzero=false ./...
+	GOEXPERIMENT=jsonv2 go tool modernize -test -fix -stringsbuilder=false -omitzero=false ./...
 
 lint-ui::
 	npm run lint
 
 license::
-	go run github.com/google/go-licenses/v2@latest check \
+	GOEXPERIMENT=jsonv2 go run github.com/google/go-licenses/v2@latest check \
 	--ignore github.com/cespare/xxhash \
 	--ignore github.com/coder/websocket \
 	--ignore github.com/cronokirby/saferith \
@@ -80,7 +80,7 @@ test-ui::
 
 test::
 	@echo "Running testsuite"
-	CGO_ENABLED=0 go test $(BUILD_TAGS) ./...
+	GOEXPERIMENT=jsonv2 CGO_ENABLED=0 go test $(BUILD_TAGS) ./...
 
 porcelain::
 	gofmt -w -l $$(find . -name '*.go')
@@ -89,7 +89,7 @@ porcelain::
 
 build::
 	@echo Version: $(VERSION) $(SHA) $(BUILD_DATE)
-	CGO_ENABLED=0 go build -v $(BUILD_TAGS) $(BUILD_ARGS)
+	GOEXPERIMENT=jsonv2 CGO_ENABLED=0 go build -v $(BUILD_TAGS) $(BUILD_ARGS)
 
 snapshot::
 	goreleaser --snapshot --skip publish --clean
diff --git a/assets/js/components/Sessions/SessionDetailsModal.vue b/assets/js/components/Sessions/SessionDetailsModal.vue
index 60d0e643d7..13eae287b0 100644
--- a/assets/js/components/Sessions/SessionDetailsModal.vue
+++ b/assets/js/components/Sessions/SessionDetailsModal.vue
@@ -80,7 +80,7 @@
 								)
 							}}
 							<div v-if="session.chargeDuration">
-								{{ fmtDurationNs(session.chargeDuration) }}
+								{{ fmtDuration(session.chargeDuration) }}
 								(~{{ fmtW(avgPower) }})
 							</div>
 						</td>
@@ -194,8 +194,7 @@ export default defineComponent({
 			return this.session.chargedEnergy * 1e3;
 		},
 		avgPower() {
-			const hours = this.session.chargeDuration / 1e9 / 3600;
-			return this.chargedEnergy / hours;
+			return this.chargedEnergy / (this.session.chargeDuration / 3600);
 		},
 		solarEnergy() {
 			return this.chargedEnergy * (this.session.solarPercentage / 100);
diff --git a/assets/js/components/Sessions/SessionTable.vue b/assets/js/components/Sessions/SessionTable.vue
index e05577fe5b..d29483e619 100644
--- a/assets/js/components/Sessions/SessionTable.vue
+++ b/assets/js/components/Sessions/SessionTable.vue
@@ -242,7 +242,7 @@ export default defineComponent({
 					unit: "h:mm",
 					total: this.chargeDuration,
 					value: (session) => session.chargeDuration,
-					format: (value) => this.fmtDurationNs(value, false, "h"),
+					format: (value) => this.fmtDuration(value, false, "h"),
 				},
 				{
 					name: "avgPower",
@@ -250,7 +250,7 @@ export default defineComponent({
 					total: this.avgPower,
 					value: (session) => {
 						if (session.chargedEnergy && session.chargeDuration) {
-							return session.chargedEnergy / this.nsToHours(session.chargeDuration);
+							return session.chargedEnergy / (session.chargeDuration / 3600);
 						}
 						return null;
 					},
@@ -339,7 +339,7 @@ export default defineComponent({
 				.reduce(
 					(total, s) => {
 						total.energy += s.chargedEnergy;
-						total.hours += this.nsToHours(s.chargeDuration);
+						total.hours += s.chargeDuration / 3600;
 						return total;
 					},
 					{ energy: 0, hours: 0 }
@@ -398,9 +398,6 @@ export default defineComponent({
 		},
 	},
 	methods: {
-		nsToHours(ns: number) {
-			return ns / 1e9 / 3600;
-		},
 		filterByLoadpoint(session: Session) {
 			return !this.loadpointFilter || session.loadpoint === this.loadpointFilter;
 		},
diff --git a/core/loadpoint/config.go b/core/loadpoint/config.go
index 3bc38d83d2..7ef83962cc 100644
--- a/core/loadpoint/config.go
+++ b/core/loadpoint/config.go
@@ -17,19 +17,19 @@ type StaticConfig struct {
 
 type DynamicConfig struct {
 	// dynamic config
-	Title                    string    `json:"title"`
-	DefaultMode              string    `json:"defaultMode"`
-	Priority                 int       `json:"priority"`
-	PhasesConfigured         int       `json:"phasesConfigured"`
-	MinCurrent               float64   `json:"minCurrent"`
-	MaxCurrent               float64   `json:"maxCurrent"`
-	SmartCostLimit           *float64  `json:"smartCostLimit"`
-	SmartFeedInPriorityLimit *float64  `json:"smartFeedInPriorityLimit"`
-	PlanEnergy               float64   `json:"planEnergy"`
-	PlanTime                 time.Time `json:"planTime"`
-	PlanPrecondition         int64     `json:"planPrecondition"`
-	LimitEnergy              float64   `json:"limitEnergy"`
-	LimitSoc                 int       `json:"limitSoc"`
+	Title                    string        `json:"title"`
+	DefaultMode              string        `json:"defaultMode"`
+	Priority                 int           `json:"priority"`
+	PhasesConfigured         int           `json:"phasesConfigured"`
+	MinCurrent               float64       `json:"minCurrent"`
+	MaxCurrent               float64       `json:"maxCurrent"`
+	SmartCostLimit           *float64      `json:"smartCostLimit"`
+	SmartFeedInPriorityLimit *float64      `json:"smartFeedInPriorityLimit"`
+	PlanEnergy               float64       `json:"planEnergy"`
+	PlanTime                 time.Time     `json:"planTime"`
+	PlanPrecondition         time.Duration `json:"planPrecondition"`
+	LimitEnergy              float64       `json:"limitEnergy"`
+	LimitSoc                 int           `json:"limitSoc"`
 
 	Thresholds ThresholdsConfig `json:"thresholds"`
 	Soc        SocConfig        `json:"soc"`
@@ -59,7 +59,7 @@ func (payload DynamicConfig) Apply(lp API) error {
 	lp.SetSmartCostLimit(payload.SmartCostLimit)
 	lp.SetSmartFeedInPriorityLimit(payload.SmartFeedInPriorityLimit)
 	lp.SetThresholds(payload.Thresholds)
-	lp.SetPlanEnergy(payload.PlanTime, time.Duration(payload.PlanPrecondition)*time.Second, payload.PlanEnergy)
+	lp.SetPlanEnergy(payload.PlanTime, payload.PlanPrecondition, payload.PlanEnergy)
 	lp.SetLimitEnergy(payload.LimitEnergy)
 	lp.SetLimitSoc(payload.LimitSoc)
 
diff --git a/server/http_config_loadpoint_handler.go b/server/http_config_loadpoint_handler.go
index 90972c6bbc..3e71b6759c 100644
--- a/server/http_config_loadpoint_handler.go
+++ b/server/http_config_loadpoint_handler.go
@@ -41,7 +41,7 @@ func getLoadpointDynamicConfig(lp loadpoint.API) loadpoint.DynamicConfig {
 		Soc:                      lp.GetSocConfig(),
 		PlanEnergy:               planEnergy,
 		PlanTime:                 planTime,
-		PlanPrecondition:         int64(planPrecondition.Seconds()),
+		PlanPrecondition:         planPrecondition,
 		LimitEnergy:              lp.GetLimitEnergy(),
 		LimitSoc:                 lp.GetLimitSoc(),
 	}
diff --git a/server/http_loadpoint_handler.go b/server/http_loadpoint_handler.go
index a8deae57c2..34709bd9fb 100644
--- a/server/http_loadpoint_handler.go
+++ b/server/http_loadpoint_handler.go
@@ -16,20 +16,11 @@ import (
 )
 
 type PlanResponse struct {
-	PlanId       int       `json:"planId"`
-	PlanTime     time.Time `json:"planTime"`
-	Duration     int64     `json:"duration"`
-	Precondition int64     `json:"precondition"`
-	Plan         api.Rates `json:"plan"`
-	Power        float64   `json:"power"`
-}
-
-type PlanPreviewResponse struct {
-	PlanTime     time.Time `json:"planTime"`
-	Duration     int64     `json:"duration"`
-	Precondition int64     `json:"precondition"`
-	Plan         api.Rates `json:"plan"`
-	Power        float64   `json:"power"`
+	PlanTime     time.Time     `json:"planTime"`
+	Duration     time.Duration `json:"duration"`
+	Precondition time.Duration `json:"precondition"`
+	Plan         api.Rates     `json:"plan"`
+	Power        float64       `json:"power"`
 }
 
 // planHandler returns the current plan
@@ -44,15 +35,19 @@ func planHandler(lp loadpoint.API) http.HandlerFunc {
 		requiredDuration := lp.GetPlanRequiredDuration(goal, maxPower)
 		plan := lp.GetPlan(planTime, requiredDuration, precondition)
 
-		res := PlanResponse{
-			PlanId:       id,
-			PlanTime:     planTime,
-			Duration:     int64(requiredDuration.Seconds()),
-			Precondition: int64(precondition.Seconds()),
-			Plan:         plan,
-			Power:        maxPower,
+		res := struct {
+			PlanId       int `json:"planId"`
+			PlanResponse `json:",inline"`
+		}{
+			PlanId: id,
+			PlanResponse: PlanResponse{
+				PlanTime:     planTime,
+				Duration:     requiredDuration,
+				Precondition: precondition,
+				Plan:         plan,
+				Power:        maxPower,
+			},
 		}
-
 		jsonWrite(w, res)
 	}
 }
@@ -101,10 +96,10 @@ func staticPlanPreviewHandler(lp loadpoint.API) http.HandlerFunc {
 		requiredDuration := lp.GetPlanRequiredDuration(goal, maxPower)
 		plan := lp.GetPlan(planTime, requiredDuration, precondition)
 
-		res := PlanPreviewResponse{
+		res := PlanResponse{
 			PlanTime:     planTime,
-			Duration:     int64(requiredDuration.Seconds()),
-			Precondition: int64(precondition.Seconds()),
+			Duration:     requiredDuration,
+			Precondition: precondition,
 			Plan:         plan,
 			Power:        maxPower,
 		}
@@ -153,10 +148,10 @@ func repeatingPlanPreviewHandler(lp loadpoint.API) http.HandlerFunc {
 		requiredDuration := lp.GetPlanRequiredDuration(soc, maxPower)
 		plan := lp.GetPlan(planTime, requiredDuration, precondition)
 
-		res := PlanPreviewResponse{
+		res := PlanResponse{
 			PlanTime:     planTime,
-			Duration:     int64(requiredDuration.Seconds()),
-			Precondition: int64(precondition.Seconds()),
+			Duration:     requiredDuration,
+			Precondition: precondition,
 			Plan:         plan,
 			Power:        maxPower,
 		}
@@ -197,12 +192,12 @@ func planEnergyHandler(lp loadpoint.API) http.HandlerFunc {
 		ts, precondition, energy := lp.GetPlanEnergy()
 
 		res := struct {
-			Energy       float64   `json:"energy"`
-			Precondition int64     `json:"precondition"`
-			Time         time.Time `json:"time"`
+			Energy       float64       `json:"energy"`
+			Precondition time.Duration `json:"precondition"`
+			Time         time.Time     `json:"time"`
 		}{
 			Energy:       energy,
-			Precondition: int64(precondition.Seconds()),
+			Precondition: precondition,
 			Time:         ts,
 		}
 
diff --git a/server/http_site_handler.go b/server/http_site_handler.go
index eca99afa1b..788bc4de28 100644
--- a/server/http_site_handler.go
+++ b/server/http_site_handler.go
@@ -1,7 +1,7 @@
 package server
 
 import (
-	"encoding/json"
+	"encoding/json/v2"
 	"errors"
 	"fmt"
 	"io"
@@ -80,8 +80,22 @@ func jsonHandler(h http.Handler) http.Handler {
 	})
 }
 
+func jsonMarshalers() *json.Marshalers {
+	return json.JoinMarshalers(
+		json.MarshalFunc(func(d time.Duration) ([]byte, error) {
+			return fmt.Append(nil, int(d.Seconds())), nil
+		}),
+		json.MarshalFunc(func(ts time.Time) ([]byte, error) {
+			if ts.IsZero() {
+				return []byte("null"), nil
+			}
+			return json.Marshal(ts)
+		}),
+	)
+}
+
 func jsonWrite(w http.ResponseWriter, data any) {
-	json.NewEncoder(w).Encode(data)
+	json.MarshalWrite(w, data, json.WithMarshalers(jsonMarshalers()))
 }
 
 func jsonError(w http.ResponseWriter, status int, err error) {
@@ -336,7 +350,7 @@ func adminPasswordValid(authObject auth.Auth, password string) bool {
 func getBackup(authObject auth.Auth) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		var req loginRequest
-		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		if err := json.UnmarshalRead(r.Body, &req); err != nil {
 			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
 		}
@@ -463,7 +477,7 @@ func resetDatabase(authObject auth.Auth, shutdown func()) http.HandlerFunc {
 			Settings bool   `json:"settings"`
 		}
 
-		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		if err := json.UnmarshalRead(r.Body, &req); err != nil {
 			jsonError(w, http.StatusBadRequest, err)
 			return
 		}
diff --git a/server/http_vehicle_handler.go b/server/http_vehicle_handler.go
index 6a2f9169e1..dc914d4ac2 100644
--- a/server/http_vehicle_handler.go
+++ b/server/http_vehicle_handler.go
@@ -107,12 +107,12 @@ func planSocHandler(site site.API) http.HandlerFunc {
 		ts, precondition, soc = v.GetPlanSoc()
 
 		res := struct {
-			Soc          int       `json:"soc"`
-			Precondition int64     `json:"precondition"`
-			Time         time.Time `json:"time"`
+			Soc          int           `json:"soc"`
+			Precondition time.Duration `json:"precondition"`
+			Time         time.Time     `json:"time"`
 		}{
 			Soc:          soc,
-			Precondition: int64(precondition.Seconds()),
+			Precondition: precondition,
 			Time:         ts,
 		}