Check out the solar tools section in the store.
I do not sell these items in our store, but I find them very useful. These are the tools that I reference in Off Grid Solar book. You may not need every one of these tools for every job, but I bring them to every installation just in case. You never want to be missing the right tool for the job.
P3 P4400 Kill-A-Watt Electricity Usage Monitor
The Kill A Watt® meter plugs into a standard AC outlet receptacle and can measure kilowatt-hours (kWh), watts (W), volts (V), amps (A), line frequency (Hz), apparent power (VA), and power factor (PF). This meter only works on the AC side of your system after the inverter. If you want to measure anything on the DC side, you need a multimeter or clamp meter. The voltage and current are measured using the accurate RMS method and the meter has over current protection.
Klein Tools CL800 AC/DC Auto-Ranging Digital Clamp Meter
Multimeters get their name because they can measure multiple things, such as voltage, current, and resistance. They are a valuable troubleshooting tool, which can help diagnose many problems in your energy system.
The simplest function is to check for continuity and this can help you ensure that sections of your circuit are as interconnected as you expected. You can check the resistance between two points in the circuit to determine if it is electrically connected.
Klein Tools MM400 Auto Ranging Digital Multimeter
Clamp Meters, also known as Current Clamps, are multimeters equipped with a clamp to measure current indirectly. Measuring current is safer with a clamp because you are not interrupting the circuit for the measurement. Instead, a clamp meter analyzes the magnetic field in a conductor, without having to make physical contact with it or disconnect it. Clamp meters are great at measuring currents over 1 ampere. Anything lower than 1 A is difficult to measure accurately with a clamp meter.
Johnson Level & Magnetic Angle Locator
This tool determines the actual tilt angle of your solar array or the roof pitch. There are some that have a magnetic bottom so you can mount it to ferrous metals and tilt to the appropriate angle.
A Solar Pathfinder
Deep Cycle Battery Hydrometer Tester
A hydrometer measures the specific gravity in flooded lead-acid batteries. By measuring the specific gravity in your batteries, you can more accurately determine the voltage of each cell and the health of your batteries. If the voltage difference between cells is 0.2 V or more, it’s time to perform an equalizing charge on the batteries. A large difference of voltage between cells is also a sign of a malfunctioning or dead battery, or possibly of sulfated cells.