Consumption is typically calculated by taking the month end reading minus month start reading.

For consumption:

You can see your start and end reading on your bill.

If you do not trust the start and end reading on your bill, you can take a picture of your meter's reading at the start of every month and then compare that with your bill. Please adhere to the safety precaution of your property when doing so. This might involve taking the caretaker with you to the meter.

Make sure to get the meter's serial (also printed on the bill in the picture).

If your meter's start and end reading does not appear on the bill, please take that up with your service providers as it is then a lot more complex to check up on your bill.

If your query is about the tariff itself:

You can download the tariff from the municipality's website.

For residential, it is typically a block tariff.

Meaning there are different blocks of electricity that are charged at different rates.

You can use the tariff from the municipality and your start and end reading to calculate your bill.

How this screen works:

So if you want to calculate what the 3rd to the 7th cost you, this screen runs 2 bills.

One from 1st to 7th.

And the next from 1st to 3rd.

Then it subtracts the second from the first.

The reason for this is because the tariff blocks only reset at the beginning of the month.