An interesting heuristic I came up with is that we should install 1 kWh of batteries for every kilowattpeak (kWp) of solar panels. On average solar panels will output around 20% of their rated peak power worldwide (see table). A good rule of thumb is that you want a minimum of 5 hours of storage in the future renewable grid. Five times 20% is 100%, hence 1 kWh of batteries for 1 kWp of solar panels.

The advantage of ocean currents is their stability. They flow with little fluctuation in speed and direction, giving them a capacity factor — a measure of how often the system is generating — of 50-70%, compared with around 29% for onshore wind and 15% for solar.