diff --git a/include/powsybl/iidm/VoltageLevel.hxx b/include/powsybl/iidm/VoltageLevel.hxx
index c7fe85c2a..c322fd072 100644
--- a/include/powsybl/iidm/VoltageLevel.hxx
+++ b/include/powsybl/iidm/VoltageLevel.hxx
@@ -71,10 +71,7 @@ stdcxx::Reference<T> VoltageLevel::getConnectable(const std::string& id) {
 
 template <typename T, typename>
 unsigned long VoltageLevel::getConnectableCount() const {
-    const auto& terminals = getTerminals();
-    return std::count_if(std::begin(terminals), std::end(terminals), [](const Terminal& terminal) {
-        return Terminal::isInstanceOf<T>(terminal);
-    });
+    return boost::size(getConnectables<T>());
 }
 
 template <typename T, typename>
diff --git a/src/iidm/Substation.cpp b/src/iidm/Substation.cpp
index a74c8ffe7..889fbccdf 100644
--- a/src/iidm/Substation.cpp
+++ b/src/iidm/Substation.cpp
@@ -54,11 +54,7 @@ Network& Substation::getNetwork() {
 }
 
 unsigned long Substation::getThreeWindingsTransformerCount() const {
-    unsigned long res = 0UL;
-    for (const auto& it : m_voltageLevels) {
-        res += it.get().getConnectableCount<ThreeWindingsTransformer>();
-    }
-    return res / 3UL;
+    return boost::size(getThreeWindingsTransformers());
 }
 
 stdcxx::const_range<ThreeWindingsTransformer> Substation::getThreeWindingsTransformers() const {
@@ -86,11 +82,7 @@ const std::string& Substation::getTso() const {
 }
 
 unsigned long Substation::getTwoWindingsTransformerCount() const {
-    unsigned long res = 0UL;
-    for (const auto& it : m_voltageLevels) {
-        res += it.get().getConnectableCount<TwoWindingsTransformer>();
-    }
-    return res / 2UL;
+    return boost::size(getTwoWindingsTransformers());
 }
 
 stdcxx::const_range<TwoWindingsTransformer> Substation::getTwoWindingsTransformers() const {
diff --git a/src/iidm/VoltageLevel.cpp b/src/iidm/VoltageLevel.cpp
index 7e56edffe..8f8e2bfda 100644
--- a/src/iidm/VoltageLevel.cpp
+++ b/src/iidm/VoltageLevel.cpp
@@ -54,10 +54,7 @@ stdcxx::range<Battery> VoltageLevel::getBatteries() {
 }
 
 unsigned long VoltageLevel::getConnectableCount() const {
-    const auto& terminals = getTerminals();
-    return std::count_if(std::begin(terminals), std::end(terminals), [](const Terminal& terminal) {
-        return terminal.getConnectable();
-    });
+    return boost::size(getConnectables<Connectable>());
 }
 
 unsigned long VoltageLevel::getDanglingLineCount() const {