I'm doing this for non-domestic in PHPP, as follows:
firstly there are use profiles for particular room types which convert hourly use into hours day and night-time per year, and have factors for relative absence which you would have to estimate. You can set up your own, similar to existing - I do this as UK schools have different hours than German for instance. Ignore lux - see below.
Then the non-dom elec uses this profile plus room data to determine daylight levels etc to work out annual hours of use and multiplies by W/m2 and m2 to get kWh. However so far I think the PHPP results are optimistic - anyone else have a view?
To get W/m2 you need to sort out the different use profiles, the m2 for each room type, and then add up the lighting wattage of each type to get W/m2. Put this into the non-dom elec sheet. These figures over-ride the figures calculated from design lux levels.
Now for domestic you could probably use the non-dom lighting calc to fudge the lighting line in electricity to get the "right" kWh/year. Now you can check IHG with this elec figure (and see what PE is too).
Finally, we have been setting the lighting engineer targets in terms of W/m2 before they start designing - eg 6 W/m2 for schools - they complain, but the result has been pretty good.
In the spirit of PH you ought to be able to light a house for 2-3 W/m2. However where you are dealing with a lighting "designer" rather than an electrical engineer all bets are off!
Alternatively if the lighting design is done using decent software it may be able to generate your W/m2 and kWh energy use figures, rather than using the non-dom elec sheet.