Preconditioning is certainly a comfort feature, preparing the cabin (and more) for the driver and passengers. It also helps prepare the batteries for charging when weather conditions aren't ideal, such as very cold and low temperatures. However, preheating inevitably requires energy, which is logically deducted from the vehicle's charging process. Especially with slower charging sources, such as 220 Volt domestic charging and with chargers generally rated no higher than 7 kW, the percentage reduction in battery charge is tangible and detrimental. In practice, the actual car charging performance decreases because that portion of "lost energy" is diverted from the battery for preheating. This also occurs on BMW cars charged with the preconditioning function activated. The most reliable solution is to monitor the power of the charging source and not assume that each charging session can fully compensate for the heating of the cabin or battery. The question is: is it really necessary to activate preconditioning? If the answer is yes, then it should be considered a charge below the maximum level. There's no problem, however, with higher-powered chargers, such as those at public charging stations, and BMW charge cable is not a problem.