Does anyone have a base load that they can't track down?
In a previous house I could get the electricity consumption down to zero but in my current place there is always something consuming power even when I think everything is turned off. I think this could be down to a mains fire alarm or ventilation system. Old doorbell transformers are another candidate but I can't see any evidence of those. It could also be the boiler.
The focus is usually on big power consumers. However, appliances that are always drawing power are also important. The area under the curve can add up to more than a powerful item used for a short time.