Enegry Meter Calculation

For modern electronic meters, you are correct. For electromechanical meters, unfortunately, that's not always the case.

The recording section (the gears from the induction disc to the dials) are a standard design, regardless of the size of the electrical service. The display register (dials) are likewise a standard design, and read directly The coils which drive the disc are not designed for full line current (if they were, they wouldn't fit in the glass envelope). CT's or shunts are used to reduce the input current to (usually) 5A full scale. Using a 400:5 CT on a 60A service would not yield the required accuracy for revenue billiing, so different CT's are used depending on the type of service. PT's may also be used if the service voltage is over 600V.

The display register shows the total KWh seen by the recording section, but that's not necessarily the same as the energy through the entire service. The meter multiplier is the product of the CT ratio and PT ratio.

Section 4.2 of the this training module gives a good explanation (actually, the entire module is a good primer).