Hydrogen cars (FCEVs) are sometimes touted as alternatives to Plug in Battery EVs (BEVs). Both cars are  Electric Vehicles in that they have batteries as well as a high efficiency electric motor or motors. The difference is basically in how the batteries get charged.  The BEV is plugged in and electricity charges the battery directly.  The FCEV has a fuel tank for hydrogen and a fuel cell for converting the hydrogen into electricity to charge the battery (very small 1.6 kwh in the Toyota Mirai for example).

Physics and economy are the primary stumbling blocks for hydrogen vehicles.  Physics because of the massive efficiency losses in converting electricity to hydrogen, then compressing it and shipping it (takes 20 times the number of trucks as it would take to ship gasoline with the same amount of energy), then finally converting it back to electricity and charging the battery. The losses are shown in the diagram below. Some indicators hint that the Toyota Mirai has a bit better efficiency than the diagram shows, but best it could do is take it from using 4x the electricity of a BEV to 3x. And this real life usage here disagrees with Toyotas early numbers.

Economy comes into play in two areas. One important one is cost at the pumps to fill up. Adding 250 miles of range to a Tesla at a supercharger can run you $12-$18. Adding 250 miles to a Toyota Mirai can cost you $75. Of course, 99% of Tesla charging will be at home so around $6 for that  250 mile fillup. Home filling of Hydrogen isn't safe or even remotely cost effective. The other problem is that that there is no infrastructure for hydrogen cars except for a handful of stations in California and one in Hawaii. 

Other miscellanious issues include: more frequent replacement of that hydrogen car battery as it is constantly filling up and draining due to its size, hydrogen takes up more space even heavily compressed in the car so takes about 2x the space as a gas tank...so bye bye storage space. Also, the hydrogen cars have less performance (see discussion below) and more maintenance.

Green Hydrogen cars use up to 4x the electricity per mile driven than a Battery EV

FCEVs would use up to 4x more electricity per mile than an EV...and would by the way be much less powerful a car (hp). Here is why:

For an EV: 48 kWh from a power station will be around 43-44 kwh by the time it reaches the motor in an EV (line losses, stepdown transformer losses, and charging losses).

For an FCEV: 48 kWh is the amount of energy required to create 1 kg of hydrogen from water. That hydrogen contains 33.3 kWh of energy. Accounting for subsequent compression electricity costs and transportation energy costs, station pumping energy cost with some leaking (hydrogen is very leakable :) ), and finally if you have an efficient fuel cell you might get 1/3 of that 33.3 kwh of energy in the hydrogen converted back into electricity (which btw then goes into a lithium ion battery pack and then eventually to the electric motor as around 11 kwh of energy).

So, 44:11 is where the 4x electricity requirement for an FCEV comes in...which means it is also 4x as dirty as a BEV (our grid is currently around 40% clean energy). Oh, why is the FCEV less powerful?  It can't convert hydrogen to electricity fast enough to supply the small battery buffer to handle high speed draws. A model 3 tesla can pull 320 kw out of its 75 kwh battery in short bursts with no problem. A much smaller battery like a hydrogen car has just can't move the electricity fast enough to the motor(s). As a result, the fastest Toyota Mirai has a 0-60 of 7.4 seconds. Much slower than a Tesla Model 3 with 3.0 second 0-60 (comparing 2020 Toyota mirai with my 2020 Tesla Model 3 Stealth...roughly same cost after discounts mirai gets).

Recent Analysis including ICE cars...similar results. Note that the EV tank to wheel losses are based on worse case numbers that include older EV designs. EVs with higher core efficiecy like Tesla Model 3s obtain massively better tank to wheel efficiency numbers...the silicon carbide dc/ac inverter in combination with the permanent magnet motors reduces that 15% loss to ~3% for a big part of the normal operating power curve.. Ditto on the charging efficiency (10% down to ~3% as measured on14-30 home charging). More info here