SMART Meter - In House Display and the WiFi password

We’re having our meter installed this week and Bulb tell me that I should give our WiFi password to the engineer, but of course we certainly can’t do that. We will type it in for him or her, but we never reveal our PW to anyone, for obvious reasons - especially someone we have never met before. In any case, we change the pw routinely every six months and would need to know how to do this with the IHD and the meters. Bulb wouldn’t want to send an engineer out every time we did this.
My question is this. If the meters communicate to the IHD by ZigBee 2,400 or 868, why is our WiFi involved?
Will we be left with documentation explaining how we can manage the HAN connection?

Our engineer didn’t connect our IHD to WiFi, I did it myself after he left, it’s really simple. Mind you it was a waste of time given how useless it is as it’s been waiting on data for almost 3 months.

If the meters communicate to the IHD by ZigBee 2,400 or 868, why is our WiFi involved?

Currently, the WiFi connection does nothing. It can potentially be used to update the firmware on your IHD, and also to allow access to higher cadence electricity usage data (10 second cadence, rather than half-hourly cadence). If such a functionality is added, then your usage data would be uploaded over your WiFi to a cloud service, either operated by Bulb or perhaps by the display manufacturer.

You’re quite right that the usage data used for billing does not require your WiFi. You can leave it disconnected with no detrimental effects. You’ll be able to control this yourself from the IHD user interface. Bulb do not provide a manual, but it seems simple enough.

Will we be left with documentation explaining how we can manage the HAN connection?

The HAN is controlled by the meter operator and is not user accessible. The WiFi is not part of the HAN.