Work out when smart heater is actually generating heat

Hi, I have a few Tuya/Smart Life devices including underfloor heating, bathroom radiators and free standing radiators. None of them seem to have HVAC_ACTION in their attributes - even though they all display on their screens a heating icon when they are actually heating (i.e the device knows it’s heating or not just not passing that info through to Home Assistant)

I’ve pasted an example of one:

hvac_modes: off, heat_cool, heat
min_temp: 7
max_temp: 30
target_temp_step: 0.5
current_temperature: 13
temperature: 12
icon: mdi:toilet
friendly_name: Bathroom Radiator 
supported_features: 1

I’m trying to work out how much energy each of these are using, seeing as they are hard wired in I can’t use an energy monitoring plug to monitor this (apart from the free standing radiator)

Anyone have a similar issue and know if there’s a way to expand the attribute list of these devices so the HVAC_ACTION appears or something else that tells me when something is actually heating or not?

I’ve explored a calculation that works out rate of change of temperate and if target temperature is less than actual temperature but it’s not very accurate!

Any help would be much appreciated thanks.