Single digit would be bad but it's much higher. From wikipedia: "current best processes for water electrolysis have an effective electrical efficiency of 70-80%

Single digit would be bad but it's much higher. From wikipedia: "current best processes for water electrolysis have an effective electrical efficiency of 70-80%,[36][37][38] so that producing 1 kg of hydrogen (which has a specific energy of 143 MJ/kg or about 40 kWh/kg) requires 50–55 kWh of electricity." Granted, converting hydrogen back to electricity has another loss of about 60% IIRC but still, you get to keep almost half of your electricity when storing it via hydrogen. So as long as solar is at most half as expensive as the second best stable energy source it's a win.