I have some questions on the Dana Dorsett article using real fuel consumption to measure heat load.

https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler

I have two factors running the calculation. The first is that my boiler is an oil burner retrofitted to burn gas. The original boiler seems to have been a 151,000 input and 131,000 out (funnily enough it looks like the same Weil-McClean in the article). When I looked at the guide on the replacement burner  they seem to have tuned it to the same 151,000 BTU input as the original.

Am I able to just use the numbers on the boiler to calculate efficiency? Or do I need to do some additional measurements?

My other issue sounds crazy. I keep the thermostat at 68 most of the time, but the house has wildly varying temperatures. Upstairs bedrooms can be 10 degree hotter and the kitchen 6-8 degrees colder (I’ve got some airsealing to do.)

Can I just use the 68 degree temperature when the real temp is that all over the place?

thanks!