diff --git a/Package.swift b/Package.swift
index cdcf32e..58db5ef 100644
--- a/Package.swift
+++ b/Package.swift
@@ -9,7 +9,6 @@ let package = Package(
   products: [
     .executable(name: "App", targets: ["App"]),
     .library(name: "ApiController", targets: ["ApiController"]),
-    .library(name: "ClimateZoneClient", targets: ["ClimateZoneClient"]),
     .library(name: "CoreModels", targets: ["CoreModels"]),
     .library(name: "LocationClient", targets: ["LocationClient"]),
     .library(name: "Routes", targets: ["Routes"]),
@@ -62,22 +61,6 @@ let package = Package(
       ],
       swiftSettings: swiftSettings
     ),
-    .target(
-      name: "LocationClient",
-      dependencies: [
-        .product(name: "Dependencies", package: "swift-dependencies"),
-        .product(name: "DependenciesMacros", package: "swift-dependencies")
-      ],
-      swiftSettings: swiftSettings
-    ),
-    .target(
-      name: "ClimateZoneClient",
-      dependencies: [
-        .product(name: "Dependencies", package: "swift-dependencies"),
-        .product(name: "DependenciesMacros", package: "swift-dependencies")
-      ],
-      swiftSettings: swiftSettings
-    ),
     .target(
       name: "CoreModels",
       dependencies: [],
@@ -94,6 +77,7 @@ let package = Package(
     .target(
       name: "LocationClient",
       dependencies: [
+        "CoreModels",
         .product(name: "Dependencies", package: "swift-dependencies"),
         .product(name: "DependenciesMacros", package: "swift-dependencies")
       ],
diff --git a/Sources/ClimateZoneClient/ClimateZoneClient.swift b/Sources/ClimateZoneClient/ClimateZoneClient.swift
deleted file mode 100644
index e69de29..0000000
diff --git a/Sources/CoreModels/ClimateZone.swift b/Sources/CoreModels/ClimateZone.swift
index a29ac47..b66960b 100644
--- a/Sources/CoreModels/ClimateZone.swift
+++ b/Sources/CoreModels/ClimateZone.swift
@@ -1,6 +1,15 @@
 import Foundation
 
-public enum ClimateZone {
+public enum ClimateZone: String, CaseIterable, Codable, Equatable, Sendable {
+
+  case one = "CZ1"
+  case two = "CZ2"
+  case three = "CZ3"
+  case four = "CZ4"
+  case five = "CZ5"
+  case six = "CZ6"
+
+  public var label: String { rawValue }
 
   public enum ZoneType: String, CaseIterable, Codable, Equatable, Sendable {
     // NOTE: Keep in this order.
@@ -35,33 +44,33 @@ public enum ClimateZone {
     public var label: String {
       return "\(self == .hotHumid ? "Hot Humid" : rawValue.capitalized) (\(zoneIdentifiers.joined(separator: ", ")))"
     }
+  }
 
-    /// Represents climate zone identifiers.
-    public enum ZoneIdentifier: String, CaseIterable, Codable, Equatable, Sendable {
-      // A zones (hotHumid)
-      case oneA = "1A"
-      case twoA = "2A"
-      // A zones (moist)
-      case threeA = "3A"
-      case fourA = "4A"
-      case fiveA = "5A"
-      case sixA = "6A"
-      case sevenA = "7A"
+  /// Represents climate zone identifiers.
+  public enum ZoneIdentifier: String, CaseIterable, Codable, Equatable, Sendable {
+    // A zones (hotHumid)
+    case oneA = "1A"
+    case twoA = "2A"
+    // A zones (moist)
+    case threeA = "3A"
+    case fourA = "4A"
+    case fiveA = "5A"
+    case sixA = "6A"
+    case sevenA = "7A"
 
-      // B zones (dry)
-      case twoB = "2B"
-      case threeB = "3B"
-      case fourB = "4B"
-      case fiveB = "5B"
-      case sixB = "6B"
-      case sevenB = "7B"
+    // B zones (dry)
+    case twoB = "2B"
+    case threeB = "3B"
+    case fourB = "4B"
+    case fiveB = "5B"
+    case sixB = "6B"
+    case sevenB = "7B"
 
-      // C zones (marine)
-      case threeC = "3C"
-      case fourC = "4C"
+    // C zones (marine)
+    case threeC = "3C"
+    case fourC = "4C"
 
-      public var label: String { rawValue }
+    public var label: String { rawValue }
 
-    }
   }
 }
diff --git a/Sources/LocationClient/LocationClient.swift b/Sources/LocationClient/LocationClient.swift
index e0ab038..ce52938 100644
--- a/Sources/LocationClient/LocationClient.swift
+++ b/Sources/LocationClient/LocationClient.swift
@@ -1,3 +1,4 @@
+@_exported import CoreModels
 import Dependencies
 import DependenciesMacros
 import Foundation
@@ -11,56 +12,132 @@ public extension DependencyValues {
 
 @DependencyClient
 public struct LocationClient: Sendable {
-  public var search: @Sendable (Int) async throws -> [Response]
 
-  // TODO: Add ClimateZone.ZoneIdentifier??
-  public struct Response: Codable, Equatable, Sendable {
+  /// Estimate the climate zone by the heating design temperature and
+  /// the state code (ex. "OH").
+  public var estimatedClimateZone:
+    @Sendable (_ heatingTemperature: Double, _ stateCode: String) async throws -> ClimateZone
 
-    public let city: String
-    public let latitude: String
-    public let longitude: String
-    public let zipCode: String
-    public let state: String
-    public let stateCode: String
-    public let county: String
+  /// Estimate the design temperatures based on location's coordinates.
+  public var estimatedDesignTemperatures: @Sendable (Coordinates) async throws -> DesignTemperatures
 
-    public init(
-      city: String,
-      latitude: String,
-      longitude: String,
-      zipCode: String,
-      state: String,
-      stateCode: String,
-      county: String
-    ) {
-      self.city = city
-      self.latitude = latitude
-      self.longitude = longitude
-      self.zipCode = zipCode
-      self.state = state
-      self.stateCode = stateCode
-      self.county = county
-    }
+  /// Get location details from a zip code.
+  public var search: @Sendable (_ zipCode: Int) async throws -> [Location]
 
-    private enum CodingKeys: String, CodingKey {
-      case city
-      case latitude
-      case longitude
-      case zipCode = "postal_code"
-      case state
-      case stateCode = "state_code"
-      case county = "province"
-    }
+  public func estimateDesignTemperaturesAndClimateZone(
+    coordinates: Coordinates,
+    stateCode: String
+  ) async throws -> (DesignTemperatures, ClimateZone) {
+    let designTemperatures = try await estimatedDesignTemperatures(coordinates)
+    let climateZone = try await estimatedClimateZone(
+      heatingTemperature: designTemperatures.heating,
+      stateCode: stateCode
+    )
+    return (designTemperatures, climateZone)
   }
+
 }
 
+struct DecodingError: Error {}
+
 extension LocationClient: TestDependencyKey {
   public static let testValue: LocationClient = Self()
 }
 
+// Intermediate response returned from 'https://app.zipcodebase.com'
+private struct IntermediateResponse: Codable, Equatable, Sendable {
+
+  let city: String
+  let latitude: String
+  let longitude: String
+  let zipCode: String
+  let state: String
+  let stateCode: String
+  let county: String
+
+  func toLocation() throws -> Location {
+    guard let longitude = Double(longitude), let latitude = Double(latitude) else {
+      throw DecodingError()
+    }
+    return .init(
+      city: city,
+      state: state,
+      stateCode: stateCode,
+      zipCode: zipCode,
+      county: county,
+      coordinates: .init(latitude: latitude, longitude: longitude)
+    )
+  }
+
+  private enum CodingKeys: String, CodingKey {
+    case city
+    case latitude
+    case longitude
+    case zipCode = "postal_code"
+    case state
+    case stateCode = "state_code"
+    case county = "province"
+  }
+}
+
+private func estimatedHeatingTemperature(_ coordinates: Coordinates) -> Double {
+  let latitude = coordinates.latitude
+  let longitude = coordinates.longitude
+
+  // Gulf coast region
+  if latitude < 31, longitude > -95 && longitude < -89 {
+    return 35
+  }
+
+  // Florida
+  if latitude < 31, longitude > -87.5 && longitude < -80 {
+    return 40
+  }
+
+  let absLat = abs(latitude)
+  if absLat < 30 { return 35 }
+  if absLat < 33 { return 30 }
+  if absLat < 36 { return 25 }
+  if absLat < 40 { return 15 }
+  if absLat < 45 { return 5 }
+  return 0
+}
+
+private func estimatedCoolingTemperature(_ coordinates: Coordinates) -> Double {
+  let latitude = coordinates.latitude
+  let longitude = coordinates.longitude
+
+  // Gulf coast and Florida
+  if latitude < 31, longitude > -95 && longitude < -80 {
+    return 95
+  }
+
+  let absLat = abs(latitude)
+  if absLat < 30 { return 95 }
+  if absLat < 33 { return 92 }
+  if absLat < 36 { return 90 }
+  if absLat < 40 { return 90 }
+  if absLat < 45 { return 88 }
+  return 85
+}
+
+private func determineClimateZone(heatingTemperature: Double, stateCode: String) -> ClimateZone {
+  let hotHumidStates = ["FL", "LA", "TX", "MS", "AL", "GA", "SC"]
+  if hotHumidStates.contains(stateCode.uppercased()) {
+    return .two
+  }
+
+  if heatingTemperature >= 45 { return .one }
+  if heatingTemperature >= 35 { return .two }
+  if heatingTemperature >= 25 { return .three }
+  if heatingTemperature >= 15 { return .four }
+  if heatingTemperature >= 5 { return .five }
+  return .six
+}
+
 #if DEBUG
 
-  public extension LocationClient.Response {
+  extension IntermediateResponse {
     static let mock = Self(
       city: "Monroe",
       latitude: "39.4413000",
diff --git a/Sources/Routes/Models/HTMXExtensions.swift b/Sources/Routes/HTMXExtensions.swift
similarity index 100%
rename from Sources/Routes/Models/HTMXExtensions.swift
rename to Sources/Routes/HTMXExtensions.swift
diff --git a/Sources/Routes/Models/Capacitor.swift b/Sources/Routes/Models/CapacitorSizing.swift
similarity index 100%
rename from Sources/Routes/Models/Capacitor.swift
rename to Sources/Routes/Models/CapacitorSizing.swift
diff --git a/Sources/Routes/Models/HeatingBalancePoint.swift b/Sources/Routes/Models/HeatingBalancePoint.swift
new file mode 100644
index 0000000..f207f0f
--- /dev/null
+++ b/Sources/Routes/Models/HeatingBalancePoint.swift
@@ -0,0 +1,50 @@
+public enum HeatingBalancePoint {
+
+  public enum Mode: String, CaseIterable, Codable, Equatable, Sendable {
+    case thermal
+  }
+
+  public enum Request: Codable, Equatable, Sendable {
+    case thermal(Thermal)
+
+    public struct Thermal: Codable, Equatable, Sendable {
+
+      public let systemSize: Double
+      public let capacityAt47: Double?
+      public let capacityAt17: Double?
+      public let heatingDesignTemperature: Double
+      public let buildingHeatLoss: Double
+
+      public init(
+        systemSize: Double,
+        capacityAt47: Double? = nil,
+        capacityAt17: Double? = nil,
+        heatingDesignTemperature: Double,
+        buildingHeatLoss: Double
+      ) {
+        self.systemSize = systemSize
+        self.capacityAt47 = capacityAt47
+        self.capacityAt17 = capacityAt17
+        self.heatingDesignTemperature = heatingDesignTemperature
+        self.buildingHeatLoss = buildingHeatLoss
+      }
+    }
+  }
+
+  public enum Response: Codable, Equatable, Sendable {
+    case thermal(Thermal)
+
+    public struct Thermal: Codable, Equatable, Sendable {
+
+      public let capacityAt47: Double
+      public let capacityAt17: Double
+      public let balancePointTemperature: Double
+
+      public init(capacityAt47: Double, capacityAt17: Double, balancePointTemperature: Double) {
+        self.capacityAt47 = capacityAt47
+        self.capacityAt17 = capacityAt17
+        self.balancePointTemperature = balancePointTemperature
+      }
+    }
+  }
+}
diff --git a/Sources/Routes/SiteRoutes.swift b/Sources/Routes/SiteRoutes.swift
index a0d6aec..7a3c0dd 100644
--- a/Sources/Routes/SiteRoutes.swift
+++ b/Sources/Routes/SiteRoutes.swift
@@ -4,6 +4,7 @@ import Foundation
 import PsychrometricClient
 @preconcurrency import URLRouting
 
+// swiftlint:disable type_body_length
 public enum SiteRoute: Equatable, Sendable {
 
   case api(Api)
@@ -392,3 +393,5 @@ public extension SiteRoute {
     }
   }
 }
+
+// swiftlint:enable type_body_length