diff --git a/src/cost-calculator.js b/src/cost-calculator.js
index c7300a5..ad8f3c9 100644
--- a/src/cost-calculator.js
+++ b/src/cost-calculator.js
@@ -29,8 +29,9 @@ function loadRatesConfig() {
 /**
  * Calculate charges from usage records applying rates and overrides.
  *
- * @param {Array} usage - Array of {account, date, core_hours}
- * @param {Object} config - Configuration with defaultRate, historicalRates, overrides
+ * @param {Array} usage - Array of {account, date, core_hours, gpu_hours}
+ * @param {Object} config - Configuration with defaultRate, defaultGpuRate,
+ * historicalRates, historicalGpuRates, overrides
  * @returns {Object} charges grouped by month then account
  */
 function calculateCharges(usage, config) {
@@ -41,23 +42,37 @@ function calculateCharges(usage, config) {
     typeof config.defaultRate === 'number' && config.defaultRate > 0
       ? config.defaultRate
       : 0;
+  const defaultGpuRate =
+    typeof config.defaultGpuRate === 'number' && config.defaultGpuRate > 0
+      ? config.defaultGpuRate
+      : 0;
   const historical = config.historicalRates || {};
+  const gpuHistorical = config.historicalGpuRates || {};
   const overrides = config.overrides || {};
 
   const charges = {};
 
   for (const record of usage) {
-    if (!record || typeof record.core_hours !== 'number' || record.core_hours <= 0) {
+    if (!record) {
       continue;
     }
     const account = record.account || 'unknown';
     const month = (record.date || '').slice(0, 7); // YYYY-MM
     const ovr = overrides[account] || {};
+    const coreHours = typeof record.core_hours === 'number' && record.core_hours > 0 ? record.core_hours : 0;
+    const gpuHours = typeof record.gpu_hours === 'number' && record.gpu_hours > 0 ? record.gpu_hours : 0;
+    if (coreHours <= 0 && gpuHours <= 0) {
+      continue;
+    }
     const rate = typeof ovr.rate === 'number'
       ? ovr.rate
       : (typeof historical[month] === 'number' ? historical[month] : defaultRate);
+    const gpuRate = typeof ovr.gpuRate === 'number'
+      ? ovr.gpuRate
+      : (typeof gpuHistorical[month] === 'number' ? gpuHistorical[month] : defaultGpuRate);
     const validRate = rate > 0 ? rate : 0;
-    let cost = record.core_hours * validRate;
+    const validGpuRate = gpuRate > 0 ? gpuRate : 0;
+    let cost = coreHours * validRate + gpuHours * validGpuRate;
     const rawDiscount = typeof ovr.discount === 'number' ? ovr.discount : 0;
     const discount = Math.min(1, Math.max(0, rawDiscount));
     if (discount > 0) {
@@ -66,9 +81,10 @@ function calculateCharges(usage, config) {
 
     if (!charges[month]) charges[month] = {};
     if (!charges[month][account]) {
-      charges[month][account] = { core_hours: 0, cost: 0 };
+      charges[month][account] = { core_hours: 0, gpu_hours: 0, cost: 0 };
     }
-    charges[month][account].core_hours += record.core_hours;
+    charges[month][account].core_hours += coreHours;
+    charges[month][account].gpu_hours += gpuHours;
     charges[month][account].cost += cost;
   }
 
@@ -76,6 +92,7 @@ function calculateCharges(usage, config) {
     for (const account of Object.keys(charges[month])) {
       const entry = charges[month][account];
       entry.core_hours = Number(entry.core_hours.toFixed(2));
+      entry.gpu_hours = Number(entry.gpu_hours.toFixed(2));
       entry.cost = Number(entry.cost.toFixed(2));
     }
   }
diff --git a/src/rates-schema.json b/src/rates-schema.json
index 9c06cbb..0a4458f 100644
--- a/src/rates-schema.json
+++ b/src/rates-schema.json
@@ -1,13 +1,17 @@
 {
   "$schema": "http://json-schema.org/draft-07/schema#",
   "title": "RatesConfig",
-  "description": "Schema for core hour rate configuration",
+  "description": "Schema for core and GPU hour rate configuration",
   "type": "object",
   "properties": {
     "defaultRate": {
       "type": "number",
       "minimum": 0
     },
+    "defaultGpuRate": {
+      "type": "number",
+      "minimum": 0
+    },
     "historicalRates": {
       "type": "object",
       "patternProperties": {
@@ -18,6 +22,16 @@
       },
       "additionalProperties": false
     },
+    "historicalGpuRates": {
+      "type": "object",
+      "patternProperties": {
+        "^[0-9]{4}-(0[1-9]|1[0-2])$": {
+          "type": "number",
+          "minimum": 0
+        }
+      },
+      "additionalProperties": false
+    },
     "overrides": {
       "type": "object",
       "patternProperties": {
@@ -28,6 +42,10 @@
               "type": "number",
               "minimum": 0
             },
+            "gpuRate": {
+              "type": "number",
+              "minimum": 0
+            },
             "discount": {
               "type": "number",
               "minimum": 0,
diff --git a/src/rates.json b/src/rates.json
index c1873e2..48665f5 100644
--- a/src/rates.json
+++ b/src/rates.json
@@ -1,17 +1,23 @@
 {
   "defaultRate": 0.02,
+  "defaultGpuRate": 0.2,
   "historicalRates": {
     "2024-01": 0.015
   },
+  "historicalGpuRates": {
+    "2024-01": 0.15
+  },
   "overrides": {
     "research": {
-      "rate": 0.01
+      "rate": 0.01,
+      "gpuRate": 0.1
     },
     "education": {
       "discount": 0.5
     },
     "special": {
       "rate": 0.025,
+      "gpuRate": 0.25,
       "discount": 0.1
     }
   }
diff --git a/src/slurmdb.py b/src/slurmdb.py
index 5398768..9377483 100644
--- a/src/slurmdb.py
+++ b/src/slurmdb.py
@@ -381,24 +381,32 @@ def export_summary(self, start_time, end_time):
             logging.error("Failed to parse rates file %s: %s", rates_path, e)
             raise
         default_rate = rates_cfg.get('defaultRate', 0.01)
+        default_gpu_rate = rates_cfg.get('defaultGpuRate', 0.0)
         overrides = rates_cfg.get('overrides', {})
         historical = rates_cfg.get('historicalRates', {})
+        gpu_historical = rates_cfg.get('historicalGpuRates', {})
 
         for month, accounts in usage.items():
             base_rate = historical.get(month, default_rate)
+            base_gpu_rate = gpu_historical.get(month, default_gpu_rate)
             for account, vals in accounts.items():
                 ovr = overrides.get(account, {})
                 rate = ovr.get('rate', base_rate)
+                gpu_rate = ovr.get('gpuRate', base_gpu_rate)
                 discount = ovr.get('discount', 0)
 
                 if rate < 0:
                     raise ValueError(f"Invalid rate {rate} for account {account}")
+                if gpu_rate < 0:
+                    raise ValueError(
+                        f"Invalid GPU rate {gpu_rate} for account {account}"
+                    )
                 if not 0 <= discount <= 1:
                     raise ValueError(
                         f"Invalid discount {discount} for account {account}"
                     )
 
-                acct_cost = vals['core_hours'] * rate
+                acct_cost = vals['core_hours'] * rate + vals.get('gpu_hours', 0.0) * gpu_rate
                 if 0 < discount < 1:
                     acct_cost *= 1 - discount
                 users = []
diff --git a/test/unit/billing_summary.test.py b/test/unit/billing_summary.test.py
index 5319d75..6b16937 100644
--- a/test/unit/billing_summary.test.py
+++ b/test/unit/billing_summary.test.py
@@ -33,11 +33,11 @@ def test_export_summary_aggregates_costs(self):
             with mock.patch.object(SlurmDB, 'fetch_invoices', return_value=invoices):
                 db = SlurmDB()
                 summary = db.export_summary('2023-10-01', '2023-10-31')
-        self.assertEqual(summary['summary']['total'], 0.2)
+        self.assertEqual(summary['summary']['total'], 1.2)
         self.assertEqual(summary['details'][0]['account'], 'acct')
         self.assertEqual(summary['details'][0]['core_hours'], 10.0)
         self.assertEqual(summary['details'][0]['gpu_hours'], 5.0)
-        self.assertEqual(summary['details'][0]['cost'], 0.2)
+        self.assertEqual(summary['details'][0]['cost'], 1.2)
         self.assertEqual(summary['summary']['gpu_hours'], 5.0)
         self.assertEqual(summary['invoices'][0]['file'], 'inv1.pdf')
 
diff --git a/test/unit/calculator.test.js b/test/unit/calculator.test.js
index 0847fdf..2f308da 100644
--- a/test/unit/calculator.test.js
+++ b/test/unit/calculator.test.js
@@ -5,31 +5,38 @@ const { calculateCharges, loadRatesConfig } = require('../../src/cost-calculator
 
 function testFileConfig() {
   const usage = [
-    { account: 'education', date: '2024-01-15', core_hours: 100 },
-    { account: 'research', date: '2024-02-01', core_hours: 50 },
-    { account: 'special', date: '2024-02-01', core_hours: 100 },
+    { account: 'education', date: '2024-01-15', core_hours: 100, gpu_hours: 10 },
+    { account: 'research', date: '2024-02-01', core_hours: 50, gpu_hours: 5 },
+    { account: 'special', date: '2024-02-01', core_hours: 100, gpu_hours: 20 },
     { account: 'other', date: '2024-02-01', core_hours: 10 }
   ];
   const config = loadRatesConfig();
   const charges = calculateCharges(usage, config);
-  assert.strictEqual(charges['2024-01'].education.cost, 100 * 0.015 * 0.5);
-  assert.strictEqual(charges['2024-02'].research.cost, 50 * 0.01);
-  assert.strictEqual(charges['2024-02'].special.cost, 100 * 0.025 * 0.9);
+  assert.strictEqual(charges['2024-01'].education.cost, (100 * 0.015 + 10 * 0.15) * 0.5);
+  assert.strictEqual(charges['2024-02'].research.cost, 50 * 0.01 + 5 * 0.1);
+  assert.strictEqual(charges['2024-02'].special.cost, (100 * 0.025 + 20 * 0.25) * 0.9);
   assert.strictEqual(charges['2024-02'].other.cost, 10 * 0.02);
+  assert.strictEqual(charges['2024-01'].education.gpu_hours, 10);
 }
 
 function testPassedConfig() {
   const usage = [
-    { account: 'acct', date: '2024-03-01', core_hours: 100 }
+    { account: 'acct', date: '2024-03-01', core_hours: 100, gpu_hours: 10 }
   ];
-  const config = { defaultRate: 0.02, historicalRates: { '2024-03': 0.03 }, overrides: { acct: { discount: 0.25 } } };
+  const config = {
+    defaultRate: 0.02,
+    defaultGpuRate: 0.2,
+    historicalRates: { '2024-03': 0.03 },
+    historicalGpuRates: { '2024-03': 0.3 },
+    overrides: { acct: { discount: 0.25 } }
+  };
   const charges = calculateCharges(usage, config);
-  assert.strictEqual(charges['2024-03'].acct.cost, 100 * 0.03 * 0.75);
+  assert.strictEqual(charges['2024-03'].acct.cost, (100 * 0.03 + 10 * 0.3) * 0.75);
 }
 
 function testInvalidUsageIgnored() {
   const usage = [
-    { account: 'bad', date: '2024-04-01', core_hours: 'NaN' }
+    { account: 'bad', date: '2024-04-01', core_hours: 'NaN', gpu_hours: 'NaN' }
   ];
   const charges = calculateCharges(usage, { defaultRate: 0.01 });
   assert.deepStrictEqual(charges, {});
@@ -77,10 +84,10 @@ function testNegativeInputs() {
   const charges = calculateCharges(usage, config);
   const may = charges['2024-05'];
   assert.ok(!('negHours' in may));
-  assert.deepStrictEqual(may.negRate, { core_hours: 5, cost: 0 });
-  assert.deepStrictEqual(may.discLow, { core_hours: 5, cost: 0.5 });
-  assert.deepStrictEqual(may.discHigh, { core_hours: 5, cost: 0 });
-  assert.deepStrictEqual(may.def, { core_hours: 5, cost: 0 });
+  assert.deepStrictEqual(may.negRate, { core_hours: 5, gpu_hours: 0, cost: 0 });
+  assert.deepStrictEqual(may.discLow, { core_hours: 5, gpu_hours: 0, cost: 0.5 });
+  assert.deepStrictEqual(may.discHigh, { core_hours: 5, gpu_hours: 0, cost: 0 });
+  assert.deepStrictEqual(may.def, { core_hours: 5, gpu_hours: 0, cost: 0 });
 }
 
 function testRoundingTotals() {
@@ -91,6 +98,7 @@ function testRoundingTotals() {
   const charges = calculateCharges(usage, { defaultRate: 0.333 });
   const june = charges['2024-06'];
   assert.strictEqual(june.round.core_hours, 0.67);
+  assert.strictEqual(june.round.gpu_hours, 0);
   assert.strictEqual(june.round.cost, 0.22);
 }