The electrical multitester is often called the "right hand" of the electrical technician, but it is limited in its ability to measure current. The clamp-on ammeter fulfills that function. With it, you can measure current through a wire without disconnecting it. And, you can measure high current flow with a small instrument. The trouble is, until recently, it was an AC-only device. In recent years, DC/AC clamp-on meters became available at reasonable prices and they include standard multitester functions. They are very valuable for troubleshooting renewable energy systems.
The better clamp-on meters include "peak hold" which records highest readings, including motor starting surges. If you work with inverters and AC generators, be sure to get one that features RMS (root mean square) measurement. It will compensate for non-sine, clipped and distorted waveforms (especially the so-called "modified sine wave") in order to give a true reading of voltage and current. You can purchase a DC/AC clamp-on multitestor for $140 to $300 from electrical and electronic suppliers. Manufacturers include Fluke, Amprobe, B&K Precision and Triplett.
When you go troubleshooting, take two multitesters. You will want to make simultaneous observations of voltage and current, or two different voltages. Get some electronic test clip wires so that you can take readings without hand-holding the probes. Read your meters' instruction manuals to learn useful and safe measuring techniques.