Alright, well I've re-done the calculations as suggested, and I've even written a program to find all of the stats for me (I'll post it later if needed). This time, I took loads of points off of the P-Q graphs of each pump, and found the power at each point. I took the average of the powers I had found (not including 0 head and 0 flow). I then took the average of all of the heads, and the average of all of the flows, then found the power that way. I then took the average (not geometric mean) of the two power values I had found to give me my value for power. That's about as accurate as it'll get. I've got here the results for the 5 pumps I did. The program I wrote will be posted later if requested when I can find somewhere to host it.
Code:
Pump Name: L20
Max Flow Rate: 685.16L/h
Max Head: 1.31m
Avg Flow Rate: 395.86L/h
Avg Head: 0.69m
Pump Power: 0.70W
Power Used: 11.00W
Efficiency: 6.33%
Pump Name: L30
Max Flow Rate: 1271.90L/h
Max Head: 2.01m
Avg Flow Rate: 747.24L/h
Avg Head: 1.00m
Pump Power: 1.90W
Power Used: 23.00W
Efficiency: 8.24%
Pump Name: Eheim 1250
Max Flow Rate: 1211.33L/h
Max Head: 2.00m
Avg Flow Rate: 638.32L/h
Avg Head: 1.18m
Pump Power: 1.93W
Power Used: 28.00W
Efficiency: 6.90%
Pump Name: Eheim 1048
Max Flow Rate: 598.10L/h
Max Head: 1.50m
Avg Flow Rate: 299.43L/h
Avg Head: 0.93m
Pump Power: 0.76W
Power Used: 10.00W
Efficiency: 7.64%
Pump Name: MCP600
Max Flow Rate: 651.09L/h
Max Head: 3.18m
Avg Flow Rate: 404.50L/h
Avg Head: 1.54m
Pump Power: 1.58W
Power Used: 9.00W
Efficiency: 17.51%