What does nominal mean?

Nominal refers to a thing's name, rather than its actual status in the present moment. The point of the term is to keep new folk from thinking that 12v literally means the system or device is running at 12.0 volts. It's usually not.

The most common uses of nominal for 'dwellers are:

The most common battery bank voltage for 'dwellers is 12v, although some run 24v or specialized, exotic voltages like 48v.¹⁾

Nominal 12v banks are rarely actually 12.0v. Examples:

• lead-acid banks can range from ~12.1v (full discharged) to something like 14.8v (absorption voltage). When full/rested they are something like ~12.7v.
• LiFePO4²⁾ lithium banks³⁾ range from ~12v discharged to ~14.6v when full.⁴⁾
• Non-LiFePO4 li-po⁵⁾ range from 9v discharged to 11.3v when rested. Just after charging you may see ~12.3v.⁶⁾

Similarly, “12v” solar panels are called that because they are used to charge/power 12v systems. The voltages on these vary even more widely:

• As low as battery voltage in the morning, ~12.1v⁷⁾
• they make max power (Pmax) at a particular voltage (Vmp) which is usually way above battery voltage, like ~18v.
• when unconnected (i.e. “open circuit”/Voc))⁸⁾ voltages are very high, like 22v.

Nominal 20v (~30Vmp) panels are common on residences in the U.S. Nominal 24v panels (~36Vmp) panels are more common in commercial installations. Solar farms may use panels of much higher voltage.