If you decide to use your house electric meter, here is a formula you can use:

kwh = 3.6 * Kh * R / T

Kh is the meter constant and usually printed on the meter. Most are 7.2.
R is the number revolutions you are timing. I use 10 when the pump is on and 1 when it is off.
T is the time in seconds for R revolutions.

If you measure with the pump off and then on and subtract the two, you get a pretty accurate number for just the pump.