Why do the UK and US EPA electricity emissions factors differ?

Question

I'm building an open source climate accounting application, and I'm looking for emissions factors of electricity generation for the same country from two different data sets. There is data from both the UK government (2020) and the EPA (2020), but the two don't agree:

According to the top half, which is eGRID data, the US generated 4,021,549,453 MWH of electricity which produced 1,654,106,291 tons of CO2e emissions, so the emissions factor should be about 0.41.

According to the bottom half, though, the UK government data shows 0.06644 for generation and 0.00434 for transmission and distribution of US electricy. So the total is only 0.07078.

Why such a big difference?

Answer 1

You need to look at how each country generates electricity, how much CO₂ does each generation method produce and how much electricity is generated by each method.

Generation  Energy    CO2
Method      Produced  Produced
             (GWh)     (Tonnes)
Coal
Gas
Diesel/Oil
Hydro
Nuclear
Solar
Wind

You will find that each country has a different mix of electricity generating methods. Britain has a significant generation from offshore wind farms, which produce little if any CO₂. It also has significantly less coal generation than it used to.

The US has a different mix.

Answer 2

Actually the reason is that these UK conversions factors are for Scope 3 (indirect) emissions from electricity in those countries. The UK does publish the direct emissions of electricity generation but only for the UK. You can see it here for only UK: