We recently returned from a week in a Norfolk cottage, a converted stable where the main living area was also a kitchen diner. The place was comfortable and pleasantly warm in the evening.
In fact I noticed the room temperature always rose slightly during the evening even though we never turned on the central heating. According to the room thermostat, the temperature tended to rise from about 20°C in the early evening to about 23°C by 11pm.
Initially puzzled, I eventually realised that the light bulbs were not the energy saving type but old fashioned incandescent bulbs. They were opalescent candle bulbs so the difference wasn’t immediately obvious. Seven 40 watt bulbs were pumping a little less than 280watts of heat into the room as soon as we switched on the lights.
At this time of year with darker evenings and summer fading away, it’s a useful effect I’d forgotten as we’ve used energy saving bulbs at home for years.
As the room thermostat was in the living room, it will only switch on the heating when the heat from the lighting becomes inadequate. Even then, it will only top up the heat from those old fashioned light bulbs.
It’s not always simple, this energy saving lark.