Why is the cost and usage graph on my online account different to my bill amount?

The graphs on your online account are an indication of your cost and usage only so they won’t exactly match your bill. There are a few reasons why your bill will differ from the graphs:

• The usage on your online graph is calculated  daily, weekly, and monthly, rather than for your billing period. This may result in small differences in total consumption between your graph and your bill.   E.g. If billing period starts on 9th of month, monthly graph will show data from 1st of month.
• If you're on a Free Time Plan, usage on your free day (e.g. Saturday) is subject to a fair usage cap of 1,200 kWh per year, or approximately 100 kWh per month. This is pro-rated at a rate of 3.29kWh per day of the billing period. Usage above the cap will be charged at the day unit rate but won’t be reflected in your graph. 
• The online graph amount includes VAT and standing charges but doesn't include the PSO levy. 

Differences between Bord Gáis Energy data and ESB Networks (ESBN) data

There’s a small difference in how Bord Gáis Energy and ESBN show time intervals in your usage data:

• Bord Gáis Energy shows the start time of each half-hour interval.
• ESBN shows the end time of each half-hour interval.

For example, If ESBN shows an interval as 12:00am, it covers the time from 11:30pm to 12:00am. Bord Gáis Energy would show this same interval as 11:30pm, since that’s when it starts.

This also affects the date shown:

• Bord Gáis Energy may show the interval as part of the previous day.
• ESBN may show it as part of the current day.