Is this a 12 or 24-volt Solar Panel?

No Such Thing as a Strict "12V" or "24V" Solar Panel

Solar panels aren't inherently classified as 12V or 24V devices. Companies use these labels for convenience based on typical pairings with battery systems rather than actual panel specifications.

Panels with a Voltage at Maximum Power Point (Vmpp) of around 18V are commonly called 12V panels because they suit 12V battery systems with PWM controllers. Similarly, "24V panels" typically have Vmpp near 36V. These are approximations, and your system's voltage requirements matter more.

Role of the Charge Controller (PWM vs. MPPT)

PWM Controllers: These directly connect panels to batteries, locking panel voltage to battery voltage. This makes panel nominal voltage more critical -- matching "12V panels" to 12V batteries or "24V panels" to 24V batteries. However, PWM controllers are less efficient and should generally be avoided.

MPPT Controllers: Modern Maximum Power Point Tracking controllers offer high efficiency and greater flexibility. An MPPT controller adjusts panel output voltage to match battery needs, allowing almost any solar panel voltage (within controller operating ranges). For example, a 39V panel could charge 12V or 24V battery banks with appropriate MPPT controllers, provided voltage limits aren't exceeded.

Key Panel Voltage Metrics

Voc (Open Circuit Voltage): The voltage a panel produces under no load. Ensure controllers can handle total combined Voc of connected panels, especially during cold temperatures when Voc rises.

Vmpp (Voltage at Maximum Power Point): Optimal operating voltage when panels produce maximum power under load. For proper MPPT function, Vmpp generally needs at least 5V above battery voltage (Victron Energy controllers specify 1V).

Takeaway: Focus on the System, Not the Panel Voltage

Consider these factors instead:

  1. Your system's battery voltage (12V, 24V, or higher)
  2. Your charge controller specifications: Does it support the panel's Voc and total input voltage? Is it MPPT or PWM?
  3. Ensure panel voltage exceeds battery voltage by an appropriate margin (typically at least +5V)

Any panel with sufficient voltage (and within controller limits) can charge a 12V or 24V system with the right MPPT charge controller.

The AnyKit Solar Calculation Software handles this automatically, calculating compatible systems including the right charge controller.