With LED's modern lighting is small fry, the killer is heating.
Indeed. Even if every LED light was on in our house, the garden and front, the cost would still be minimal. Almost every bulb we have is dimmable, and often on 50% brightness or less, so I'd guess every bulb on at once might be 150W. In reality, likely nearer 80-100W. But they're
never always on.
From remote monitoring during my recent holiday, the 'base' load at home was around £1.10 a day for electricity and 20p for gas (heating hot water on a timer) - excluding service charge. That's keeping the fridge/freezer and a second freezer on, as well as the router (to keep two security cameras going) and boiler (to heat the water). Almost every socket was turned off and I even turned off the lighting circuits as smart bulbs can use up to 0.5W even when turned off (I am not sure the exact power consumption, as the bulbs use Zigbee which is low energy).
On a normal average day when at home, we'll spend around £2-3. Maybe a bit over £3 if using the oven for an hour or so, or use the washing machine. More again if using the dryer. Those are all the things that make a noticeable difference.
When I used the air con during the hottest days of the year, it jumped to £8+! However, for a good night sleep that was money well spent. However, if hotter days become the norm in the next 5+ years then it's going to be an issue - for me and everyone. I'd likely invest in a split system to save money and increase efficiency, but it's still a hefty cost at a time when people have been used to saving money due to not needing to heat their home. Cooling a home is a big expense nobody is likely prepared for.