The Bolt EV will have a very powerful heater. Significantly more powerful than the Gen II Volt. Though they wouldn't tell me how powerful. However the amount of coolant in the heating system is much less (compared to the Gen II Volt). This leads to faster warm up times and also a lot of attention was payed to the heat exchangers to get heat into the cabin efficiently. They claimed they were pushing coolant into passageways so small that it pushes the limits of the coolant they are using.