I would say H4, as I'm not aware of any 2 cylinder Prius models. I believe H2 would be an error that happened when someone added their car to the database. (Hopefully one of the tech guys on that end of things can chime in and confirm my hypothesis.
I want to take this time to point out that the engine types tend to be confusing in general. Most recent I was looking at the Golf diesels here, and there was 2 to 3 diesel engine types under the filter. In US, we only get the 2.0L. Overseas, they have a 1.6L and maybe more options. The codes don't give a basic displacement, and leave a user going through by trial and error.
It's very confusing having so many engine options in one car. Like you say, the Golf here has a 1.2 TSI, a 1.4 TSI, a 1.6 TDI, a 1.9 TDI, a 2.0 litre TSI (GTI) and a 2.0 litre TDI, all of those engines have different power outputs, then there are also different varients too, GT, GTI, GTTDI, GTD, TDI, TSI. This is another reason ive never been a fan of german cars, too many choices!
Wouldn't recommend a fully electric car, most people overlook the fact that only 5% of the population will want to buy it off you when you're ready to sell it on, I've seen depreciation as high as £3 per mile or $4.75 in some cases!
Electric might work fairly well in some parts of Europe where I think distances are short but they just don't have the range for much of the US. It's 887 miles or 1427 kilometers. or about the same as Connecticut to South Carolina.