The majority of PHEVs can only accept a maximum charge of 3.7kW, whereas full EVs can accept 7.4kW and more, so if you are looking for a home charger then a 3.7kW would be sufficient. However, some home chargers allow you to switch between the two settings, so if there's a possibility you may change to a full EV at some point in the future it may be a sensible to go for a charger that can deliver 7.4kW - even if you choose one without the switching capability your PHEV will charge at the maximum rate it is capable of.