diff --git a/src/main/kotlin/com/frankenergie/smartasset/config/ChargingGroupsConfig.kt b/src/main/kotlin/com/frankenergie/smartasset/config/ChargingGroupsConfig.kt
new file mode 100644
index 0000000..a25ee54
--- /dev/null
+++ b/src/main/kotlin/com/frankenergie/smartasset/config/ChargingGroupsConfig.kt
@@ -0,0 +1,25 @@
+package com.frankenergie.smartasset.config
+
+import com.frankenergie.smartasset.model.ChargingGroup
+import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
+import java.math.BigDecimal
+import java.time.LocalDate
+import java.time.LocalDateTime
+
+@Configuration
+class ChargingGroupsConfig {
+
+    @Bean
+    fun chargingGroups(): List<ChargingGroup> {
+        val today = LocalDate.now()
+        return listOf(
+            ChargingGroup("A", today.atTime(0, 0), today.atTime(8, 30), BigDecimal("5"), BigDecimal("2")),
+            ChargingGroup("B", today.atTime(0, 0), today.atTime(11, 0), BigDecimal("10"), BigDecimal("3")),
+            ChargingGroup("C", today.atTime(13, 0), today.atTime(18, 0), BigDecimal("4"), BigDecimal("1")),
+            ChargingGroup("D", today.atTime(13, 0), today.atTime(21, 0), BigDecimal("20"), BigDecimal("6")),
+            ChargingGroup("E", today.atTime(17, 30), today.atTime(22, 0), BigDecimal("5"), BigDecimal("2")),
+            ChargingGroup("F", today.atTime(17, 30), today.plusDays(1).atTime(0, 0), BigDecimal("15"), BigDecimal("5"))
+        )
+    }
+}
diff --git a/src/main/kotlin/com/frankenergie/smartasset/model/ChargingOrder.kt b/src/main/kotlin/com/frankenergie/smartasset/model/ChargingOrder.kt
new file mode 100644
index 0000000..50855da
--- /dev/null
+++ b/src/main/kotlin/com/frankenergie/smartasset/model/ChargingOrder.kt
@@ -0,0 +1,12 @@
+package com.frankenergie.smartasset.model
+
+import java.math.BigDecimal
+import java.time.LocalDateTime
+
+data class ChargingGroup(
+    val id: String,
+    val startTime: LocalDateTime,
+    val endTime: LocalDateTime,
+    val neededChargeMWh: BigDecimal,
+    val maxPowerMW: BigDecimal
+)
diff --git a/src/main/kotlin/com/frankenergie/smartasset/model/ChargingPlan.kt b/src/main/kotlin/com/frankenergie/smartasset/model/ChargingPlan.kt
new file mode 100644
index 0000000..b7fefed
--- /dev/null
+++ b/src/main/kotlin/com/frankenergie/smartasset/model/ChargingPlan.kt
@@ -0,0 +1,14 @@
+package com.frankenergie.smartasset.model
+
+import java.math.BigDecimal
+
+data class ChargingPlan(
+    val groupAllocations: List<GroupAllocation>,
+    val totalCost: BigDecimal
+) {
+    val averagePricePerMWh: BigDecimal
+        get() {
+            val totalMWh = groupAllocations.sumOf { it.totalMWh }
+            return if (totalMWh > BigDecimal.ZERO) totalCost.divide(totalMWh, 2, java.math.RoundingMode.HALF_UP) else BigDecimal.ZERO
+        }
+}
diff --git a/src/main/kotlin/com/frankenergie/smartasset/model/GroupAllocation.kt b/src/main/kotlin/com/frankenergie/smartasset/model/GroupAllocation.kt
new file mode 100644
index 0000000..e6fc838
--- /dev/null
+++ b/src/main/kotlin/com/frankenergie/smartasset/model/GroupAllocation.kt
@@ -0,0 +1,11 @@
+package com.frankenergie.smartasset.model
+
+import java.math.BigDecimal
+import java.time.LocalDateTime
+
+data class GroupAllocation(
+    val groupId: String,
+    val allocations: List<QuarterAllocation>,
+    val totalMWh: BigDecimal,
+    val totalCost: BigDecimal
+)
diff --git a/src/main/kotlin/com/frankenergie/smartasset/model/QuarterAllocation.kt b/src/main/kotlin/com/frankenergie/smartasset/model/QuarterAllocation.kt
new file mode 100644
index 0000000..6d76fb1
--- /dev/null
+++ b/src/main/kotlin/com/frankenergie/smartasset/model/QuarterAllocation.kt
@@ -0,0 +1,13 @@
+package com.frankenergie.smartasset.model
+
+import java.math.BigDecimal
+import java.time.LocalDateTime
+
+data class QuarterAllocation(
+    val startTime: LocalDateTime,
+    val endTime: LocalDateTime,
+    val mwh: BigDecimal,
+    val pricePerMWh: BigDecimal
+) {
+    val cost: BigDecimal get() = mwh * pricePerMWh
+}
diff --git a/src/main/kotlin/com/frankenergie/smartasset/service/ChargingOptimizedService.kt b/src/main/kotlin/com/frankenergie/smartasset/service/ChargingOptimizedService.kt
new file mode 100644
index 0000000..88be3c5
--- /dev/null
+++ b/src/main/kotlin/com/frankenergie/smartasset/service/ChargingOptimizedService.kt
@@ -0,0 +1,76 @@
+package com.frankenergie.smartasset.service
+
+import com.frankenergie.smartasset.domain.OrderBook
+import com.frankenergie.smartasset.model.*
+import org.springframework.stereotype.Service
+import java.math.BigDecimal
+import java.time.LocalDateTime
+
+@Service
+class ChargingOptimizerService {
+    private val quarterDurationHours = BigDecimal("0.25")
+
+    fun optimize(
+        groups: List<ChargingGroup>,
+        orderBook: OrderBook,
+        chargedSoFar: Map<String, BigDecimal> = emptyMap()
+    ): ChargingPlan {
+        val groupAllocations = groups.map { group ->
+            optimizeGroup(group, orderBook, chargedSoFar[group.id] ?: BigDecimal.ZERO)
+        }
+
+        val totalCost = groupAllocations.sumOf { it.totalCost }
+        return ChargingPlan(groupAllocations, totalCost)
+    }
+
+    private fun optimizeGroup(
+        group: ChargingGroup,
+        orderBook: OrderBook,
+        alreadyCharged: BigDecimal
+    ): GroupAllocation {
+        val remainingNeed = (group.neededChargeMWh - alreadyCharged).max(BigDecimal.ZERO)
+        val maxPerQuarter = group.maxPowerMW * quarterDurationHours
+        val quarters = getQuartersInWindow(group.startTime, group.endTime)
+
+        val quartersWithPrices = quarters.mapNotNull { period ->
+            val bestAsk = orderBook.getBestAsk(period)
+            bestAsk?.let { period to it.price }
+        }.sortedBy { it.second }
+
+        val allocations = mutableListOf<QuarterAllocation>()
+        var allocated = BigDecimal.ZERO
+
+        for ((period, price) in quartersWithPrices) {
+            if (allocated >= remainingNeed) break
+
+            val toAllocate = maxPerQuarter.min(remainingNeed - allocated)
+            allocations.add(
+                QuarterAllocation(
+                    startTime = period.startTime,
+                    endTime = period.endTime,
+                    mwh = toAllocate,
+                    pricePerMWh = price
+                )
+            )
+            allocated += toAllocate
+        }
+
+        return GroupAllocation(
+            groupId = group.id,
+            allocations = allocations,
+            totalMWh = allocated,
+            totalCost = allocations.sumOf { it.cost }
+        )
+    }
+
+    private fun getQuartersInWindow(start: LocalDateTime, end: LocalDateTime): List<DeliveryPeriod> {
+        val quarters = mutableListOf<DeliveryPeriod>()
+        var current = start
+        while (current < end) {
+            val quarterEnd = current.plusMinutes(15)
+            quarters.add(DeliveryPeriod(current, quarterEnd.coerceAtMost(end)))
+            current = quarterEnd
+        }
+        return quarters
+    }
+}
diff --git a/src/test/kotlin/com/frankenergie/smartasset/service/ChargingOptimizerServiceTest.kt b/src/test/kotlin/com/frankenergie/smartasset/service/ChargingOptimizerServiceTest.kt
new file mode 100644
index 0000000..fbf7433
--- /dev/null
+++ b/src/test/kotlin/com/frankenergie/smartasset/service/ChargingOptimizerServiceTest.kt
@@ -0,0 +1,134 @@
+package com.frankenergie.smartasset.service
+
+import com.frankenergie.smartasset.domain.OrderBook
+import com.frankenergie.smartasset.model.ChargingGroup
+import com.frankenergie.smartasset.model.DeliveryPeriod
+import com.frankenergie.smartasset.model.OrderSide
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import java.math.BigDecimal
+import java.time.LocalDateTime
+
+class ChargingOptimizerServiceTest {
+
+    private lateinit var optimizer: ChargingOptimizerService
+    private lateinit var orderBook: OrderBook
+
+    @BeforeEach
+    fun setUp() {
+        optimizer = ChargingOptimizerService()
+        orderBook = OrderBook()
+    }
+
+    @Test
+    fun `optimize returns empty allocations when no sell orders`() {
+        val group = ChargingGroup(
+            id = "A",
+            startTime = LocalDateTime.of(2024, 1, 15, 10, 0),
+            endTime = LocalDateTime.of(2024, 1, 15, 11, 0),
+            neededChargeMWh = BigDecimal("1"),
+            maxPowerMW = BigDecimal("2")
+        )
+
+        val plan = optimizer.optimize(listOf(group), orderBook)
+
+        assertEquals(1, plan.groupAllocations.size)
+        assertTrue(plan.groupAllocations[0].allocations.isEmpty())
+        assertEquals(BigDecimal.ZERO, plan.totalCost)
+    }
+
+    @Test
+    fun `optimize allocates cheapest quarters first`() {
+        val group = ChargingGroup(
+            id = "A",
+            startTime = LocalDateTime.of(2024, 1, 15, 10, 0),
+            endTime = LocalDateTime.of(2024, 1, 15, 11, 0),
+            neededChargeMWh = BigDecimal("0.50"),
+            maxPowerMW = BigDecimal("2")
+        )
+
+        val q1 = DeliveryPeriod(LocalDateTime.of(2024, 1, 15, 10, 0), LocalDateTime.of(2024, 1, 15, 10, 15))
+        val q2 = DeliveryPeriod(LocalDateTime.of(2024, 1, 15, 10, 15), LocalDateTime.of(2024, 1, 15, 10, 30))
+        val q3 = DeliveryPeriod(LocalDateTime.of(2024, 1, 15, 10, 30), LocalDateTime.of(2024, 1, 15, 10, 45))
+
+        orderBook.processOrder(q1, OrderSide.SELL, BigDecimal("10"), BigDecimal("60.00"))
+        orderBook.processOrder(q2, OrderSide.SELL, BigDecimal("10"), BigDecimal("40.00"))
+        orderBook.processOrder(q3, OrderSide.SELL, BigDecimal("10"), BigDecimal("50.00"))
+
+        val plan = optimizer.optimize(listOf(group), orderBook)
+
+        val allocation = plan.groupAllocations[0]
+        assertEquals(1, allocation.allocations.size)
+        assertEquals(BigDecimal("40.00"), allocation.allocations[0].pricePerMWh)
+    }
+
+    @Test
+    fun `optimize respects max power constraint`() {
+        val group = ChargingGroup(
+            id = "A",
+            startTime = LocalDateTime.of(2024, 1, 15, 10, 0),
+            endTime = LocalDateTime.of(2024, 1, 15, 10, 30),
+            neededChargeMWh = BigDecimal("1"),
+            maxPowerMW = BigDecimal("2") // max 0.5 MWh per quarter
+        )
+
+        val q1 = DeliveryPeriod(LocalDateTime.of(2024, 1, 15, 10, 0), LocalDateTime.of(2024, 1, 15, 10, 15))
+        val q2 = DeliveryPeriod(LocalDateTime.of(2024, 1, 15, 10, 15), LocalDateTime.of(2024, 1, 15, 10, 30))
+
+        orderBook.processOrder(q1, OrderSide.SELL, BigDecimal("10"), BigDecimal("50.00"))
+        orderBook.processOrder(q2, OrderSide.SELL, BigDecimal("10"), BigDecimal("50.00"))
+
+        val plan = optimizer.optimize(listOf(group), orderBook)
+
+        val allocation = plan.groupAllocations[0]
+        assertEquals(2, allocation.allocations.size)
+        assertEquals(BigDecimal("0.50"), allocation.allocations[0].mwh)
+        assertEquals(BigDecimal("0.50"), allocation.allocations[1].mwh)
+    }
+
+    @Test
+    fun `optimize accounts for already charged energy`() {
+        val group = ChargingGroup(
+            id = "A",
+            startTime = LocalDateTime.of(2024, 1, 15, 10, 0),
+            endTime = LocalDateTime.of(2024, 1, 15, 10, 30),
+            neededChargeMWh = BigDecimal("1"),
+            maxPowerMW = BigDecimal("2")
+        )
+
+        val q1 = DeliveryPeriod(LocalDateTime.of(2024, 1, 15, 10, 0), LocalDateTime.of(2024, 1, 15, 10, 15))
+        val q2 = DeliveryPeriod(LocalDateTime.of(2024, 1, 15, 10, 15), LocalDateTime.of(2024, 1, 15, 10, 30))
+
+        orderBook.processOrder(q1, OrderSide.SELL, BigDecimal("10"), BigDecimal("50.00"))
+        orderBook.processOrder(q2, OrderSide.SELL, BigDecimal("10"), BigDecimal("50.00"))
+
+        val chargedSoFar = mapOf("A" to BigDecimal("0.50"))
+        val plan = optimizer.optimize(listOf(group), orderBook, chargedSoFar)
+
+        val allocation = plan.groupAllocations[0]
+        assertEquals(BigDecimal("0.50"), allocation.totalMWh)
+    }
+
+    @Test
+    fun `optimize calculates total cost correctly`() {
+        val group = ChargingGroup(
+            id = "A",
+            startTime = LocalDateTime.of(2024, 1, 15, 10, 0),
+            endTime = LocalDateTime.of(2024, 1, 15, 10, 30),
+            neededChargeMWh = BigDecimal("1"),
+            maxPowerMW = BigDecimal("4")
+        )
+
+        val q1 = DeliveryPeriod(LocalDateTime.of(2024, 1, 15, 10, 0), LocalDateTime.of(2024, 1, 15, 10, 15))
+        val q2 = DeliveryPeriod(LocalDateTime.of(2024, 1, 15, 10, 15), LocalDateTime.of(2024, 1, 15, 10, 30))
+
+        orderBook.processOrder(q1, OrderSide.SELL, BigDecimal("10"), BigDecimal("40.00"))
+        orderBook.processOrder(q2, OrderSide.SELL, BigDecimal("10"), BigDecimal("60.00"))
+
+        val plan = optimizer.optimize(listOf(group), orderBook)
+
+        // Should use q1 fully (1 MWh at 40) = 40 EUR
+        assertEquals(0, BigDecimal("40.00").compareTo(plan.totalCost))
+    }
+}