You should begin by trying to collect this data. Even though this can be hard, we have prepared a template that makes this "ask" a lot simpler. You can share the associated tab from the measurement workbook to let your manufacturers self-report this data.

Explain that they should report energy used to make your products. They can assess this simply by taking the % that your products represent in their output and applying it to their total energy use. The total doesn't need to be reported.

You can choose to accept the BEE's estimate if you truly can't get the data from your supplier.