KWH readings, line and load side of transformer

would the KWH readings be the same on the line side of a 480 volt transformer and the 208 load side of the transformer minus the efficiency effects?

By math, yes.

Welcome to ECN

Thank you.Installing Emon-Demon system for tenant metering

The difference should be a fairly accurate measurement of the various losses in the transformer and associated wiring.
Virtually all of the loss is eventually going to end up as heat, as is the case in anything electrical.
When we were calculating HVAC loads in computer rooms the sensible heat always included the total electrical input to the room at 100%. (3412.142 BTU per KWH, usually rounded off to 3400)

Just an FYI, follow the Emon install instructions...

Yes, it was designed by an engineer who shows 2 sets of ct,s on the load side of transformers. This will work in favor of the tenant. I would correct this but they sent 208v meters, need 480v meters to make it work. The landlord will have to take the heat.

If the tenant is actually supposed to pay for what they use, the CTs should be on the load side of the transformer.
The transformer is the landlord's equipment and he needs to recover that money somewhere else in the rent, just like he has to do with parking lot lights and exit signs.

Thanks for the input, system is up and running. Now it is time to teach the landlord how to read and bill for KWH & demand

I assume this is sub metering (landlord owned meters). He will need to compare the total PoCo bill to what he records for each tenant and consider the difference "house load" and recover that in another manner.
I am not sure where you are but in Florida they have to bill sub metered power at the same rate they pay, including all attached fees. They can't tack on a landlord service fee or increased rate as part of the power bill.
Prior to that law, there was lots of abuse. Places like trailer parks were marking up the power 100%.

Be sure that he doesn't make a profit on the resale of electricity. Even if it's an honest mistake you risk being on the wrong side of the law.
Their best bet would be to contact the local Utility to make sure that they're allocating the electric costs properly and within the rules.
Here in ComEd territory...resale isn't allowed no matter how you split up the bill (which is overkill IMHO).