Measures I've taken in the house: replacing all the old E14 / E27 incandescent light bulbs with LED (I swear by Osram or Philips).
Even the T5 / T8 tubes where possible (kitchen, laundry room). Or in the case of the bathroom, we replaced the whole G9 fixture with an LED-version.
I had a twin-T12 leftover industrial fixture over my work bench for a time, and my brain was getting slowly cooked from the heat.
Replaced it with a pair of 600x600 Ledvance LED-panels, and I was so happy! Not just from the instant illumination, but also from no longer feeling the wasted energy turned into heat over my head.
Turn the lights off in rooms that are vacant or not in regular use. Close the doors to preserve heat in the rooms. Lower the temperature by even 1-2°C can make a big difference over time. Lower the thermostat from 20°C til 18ºC and buy an extra sweater and / or blanket.
Use the wood burning stove more, if you have one, instead of relying mostly on the electric heaters or heat pump (we are sinning on this when it's a steady -20°C or colder outside for weeks at a time). And if the stove is in another room or adjacent to the living room, use a cheap floor fan to spread the warmth from the stove faster.
My personal favourite for getting warm: do a long gaming session, getting that high-end CPU and GPU nice and toasty. It's a perfect foot warmer, and you're having fun at the same time!