When running this on a desktop, without a battery, the applet is blank, and this is printed to the terminal: file:///usr/lib64/qt5/qml/org/kde/kirigami.2/templates/InlineMessage.qml:259:9: QML ActionToolBar: Binding loop detected for property "atBottom" file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:44: Error: Cannot assign [undefined] to QObject* file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'temperature' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'energyFullDesign' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'energyFull' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'energy' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'voltage' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'energyRate' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'technology' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'serial' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'capacity' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'chargePercent' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'chargeState' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'rechargeable' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'temperature' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'energyFullDesign' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'energyFull' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'energy' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'voltage' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'energyRate' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'technology' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'serial' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'capacity' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'chargePercent' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'chargeState' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/main.qml:483: TypeError: Cannot read property 'rechargeable' of null file:///usr/share/kpackage/kcms/kcm_energyinfo/contents/ui/Graph.qml:68: TypeError: Cannot read property 'x' of undefined Via system settings, this KCM is not exposed on desktop, so it's not much of an issue there. However, its accessible directly via kinfocenter.
I think this has been fixed by https://invent.kde.org/plasma/kinfocenter/-/merge_requests/40