[Moustachauve]

EnergySensor previously subclassed Home Assistant Core's private IntegrationSensor class directly to estimate cumulative energy from device power readings. Because IntegrationSensor is an internal helper entity rather than a public base class, upstream constructor changes in Home Assistant 2026.2 and 2026.11 (#1106) repeatedly broke Hilo setups and required fragile version-checking branches, entity registry workarounds to resolve the source power entity_id, and state machine listeners.

Having EnergySensor inherit directly from HiloEntity and RestoreSensor removes all coupling to homeassistant.components.integration and avoids future breakage when Home Assistant Core modifies its internal helper classes. Instead of watching another entity in the state machine by string ID, EnergySensor now computes the Left-Riemann sum directly from the in-memory HiloDevice power attribute whenever the device updates (via SignalR or coordinator polling) as well as on a 5-minute fallback timer for constant-power periods. Full Decimal precision is retained across intervals internally while rounding native_value to 2 decimal places so small energy increments are never lost to per-tick rounding.

Existing installations migrate seamlessly without losing historical statistics or requiring reconfiguration: entity unique_ids, device classes, and TOTAL_INCREASING state classes are unchanged, and async_added_to_hass restores previous totals from both standard RestoreSensor native data and legacy IntegrationSensor extra data (last_valid_state). Moving the accumulation state onto pyhilo's HiloDevice is noted for a follow-up refactor once device update lifecycles are consolidated in the library.

Pros	Cons
No longer subclasses HA's internal IntegrationSensor, which broke in 2026.2 and 2026.11 (#1106) and needed version checks.	We maintain the Left-Riemann calculation (power * dt / 3,600,000) ourselves instead of delegating it to HA.
Reads power directly from HiloDevice in memory instead of watching a sibling sensor.*_power entity in the state machine.
Renaming or disabling a power sensor entity in HA no longer breaks energy tracking.
Updates on every SignalR push and coordinator poll (plus a 5-min fallback timer instead of 15-min), even when wattage is constant.
Keeps existing unique_ids and restores state from both RestoreSensor and legacy IntegrationSensor storage.
Easier to move into pyhilo later since it only depends on device power updates.