I worked out an accurate calorie figure by tracking what I ate and exercised in myfitness pal and weighing myself once a week. Over a 6-8 week period I concluded that if I eat a net of 1500kcal I lose 0.5-0.75kg a week and a net of 1800-2000kg maintains my weight.
By net I mean after exercise. So my actual food consumption is more on days I exercise.
Even at the most scientific level measuring energy expenditure is based on estimations. Even if you had access to expensive Air Displacement Plethysmography (this is a gold standard method of assessing body composition which is a big factor in energy expenditure) it would still be based on estimates. We can only estimate better.
There is an institute in the USA where they conduct studies with subjects in one room the entire duration and they can monitor the oxygen consumption very precisely. I can’t for the life of me find the name though. Obviously not suggesting you head to the USA though!