Summing up Power Plant Data

I would like to get the power plant capacities from the 2015 Form EIA-860 Data on Generators (download the ZIP).
The data there is give for individual generators (blocks), but no totals for power plants.

ID Plant Block Nameplate Capacity

8102 General James M Gavin 1 1,300.0

8102 General James M Gavin 2 1,300.0

So I would like to add up the Nameplate Capacities for all rows with the same ID:

8102 General James M Gavin 2,600.0

How can I achieve this with Calc?
Thanks in advance…

Have you considered a pivot table?

Yes, now I have a pivot table. But how can I sort such without destroying it?

Can you explain more? How is it being “destroyed” when you sort?