It’s a common misconception that Passive houses require no energy or additional heating, I was guilty of it myself until not too long ago.
Passive houses must fulfil a range of criteria before they can be certified as passive but the main one is that the heating load should be less than 10 W/m² whilst maintaining an indoor temperature of 20°C. So on the coldest day of the year a 200m² house should require no more than 2000w of heat to keep the entire house at 20°C, a two bar electric heater would do the job.
But it is true to say that because of the way the BER is calculated many passive houses don’t get an A1 BER rating as one might expect.
As has been discussed here previously the BER system certainly has it’s flaws particularly as it is mostly a paper exercise but it is definitely better than what we had before i.e. nothing!