There are so many numbers and technical terms around solar panels and solar panel output voltage that finding the information you're looking for can be a headache. Figuring out the solar panel voltage can feel like looking for a needle in a haystack.
Fear not; it’s more simple than it might look at first. We’re here to tell you all about solar panel voltage and solar energy and everything you need to know about solar power energy. Voltage is directly related to how much energy a solar panel produces.
Below, we cover what we believe to be the most critical solar panel output voltage concepts and related terms that will enable you to make an informed decision whenever you plan to buy a solar panel.
Solar Panel Output Voltage
When talking about solar panel output voltage, it’s essential to get the definitions straight as voltage can refer to many things:
(i) Nominal Voltage
Nominal voltage is not actual voltage but rather a category or classification that is more related to the battery that will be charged.
(ii) Potential or Open-circuit Voltage (VoC)
VoC is the measurement of the voltage in a circuit verified with a voltmeter, without a load being connected.
(iii) Voltage at Maximum Power (Vmp)
Vmp is the voltage available when the panel, operating at maximum capacity, is connected to a load. Because voltage is inversely proportional to the resistance of a circuit, the fact that there’s no load connected will change the voltage.
(iv) Actual Voltage Measured Under Load
This is the actual voltage of the circuit once a load (an appliance like a heater, phone charger, etc.) is connected to it.
(v) AC Volts
AC Volts is the voltage after an inverter has converted DC Volts to AC Volts.
In various articles, solar panel output voltage refers to either nominal voltage, the open-circuit voltage at maximum power, or actual voltage. Because the exact kind of voltage each article is referring to, the output voltage can quickly become blurred.
This article will use output voltage to refer to the potential or open-circuit voltage or Voc (measured with a voltmeter without connecting a load).
Nevertheless, we will also consider the other voltage dimensions (Vmp, actual voltage under load, etc.) and the relationship between the panel, the batteries, and the inverter.
How Solar Power Works
Solar panels (flat plate collectors) and solar cells convert sunlight energy into power or light energy into electrical energy.
Particles of light released by the sun are collected by the solar panel to convert into usable energy.
Each solar cell consists of a thin semiconductor made up of two layers of silicon. When the sun’s light strikes the solar cell, they activate the cell by knocking the electrons loose within the semiconductor. These electrons move through the solar panel’s circuit, and the movement generates a direct electrical current or DC energy.
How Solar Power Cell Voltage Works
A single solar cell produces an open-circuit voltage or electrical potential of approximately 0.5 to 0.6 volts. The voltage of a cell under load is approximately 0.46 volts, generating a current of about 3 amperes.
The power that one cell produces is, in other words, approximately 1.38 watts (voltage multiplied by current).
A solar panel consists of a collection of solar cells.
In terms of the voltage required by solar panels to charge batteries, manufactured panels can charge 12 volt or 24-volt batteries as a rule of thumb. For example, a standard panel consisting of 36 crystalline silicon cells will give a peak open-circuit voltage output (Voc) of approximately 18 to 21 volts, which on load will reduce to about 12-14 volts, enough to charge a 12-volt battery.
You should also consider that the battery charged by the panel(s) will link to an inverter that converts the DC voltage to AC voltage (e.g., 12 volts DC to 120 volts AC).
Solar power, Solar Energy Efficiency, and Panel Preference
It’s essential to weigh up your panel’s solar panel voltage output potential with its solar panel efficiency as we cannot view the two aspects in isolation.
Energy efficiency is the percentage of sunlight that hits the panel that’s turned into energy.
One of the factors that affect energy efficiency is the design of the panel to capture the energy of the sun.
Monocrystalline or single silicon panels are arguably some of the most efficient solar panels designs available on the market (approximately 18-22% efficient).
Polycrystalline or multi-layered silicone panels are, on average, a bit less efficient than their monocrystalline counterparts but with less silicone. They’re also a bit cheaper and more resistant to cold (approximately 14-19% efficient).
Solar Panel Life Expectancy
Regardless of the solar power output and efficiency, you should also consider your solar panel’s life expectancy. The power output will be less in the event of degradation during the lifespan of a solar panel.
Most crystalline panels are guaranteed for 25 years, while thin-film panels are usually not guaranteed for more than 5 years. In reality, the guaranteed 25 years of crystalline panels can creep up to 40 years if the panels are well maintained.
The degradation during this period occurs for various reasons such as normal wear and tear, wind, sun, snow, and eventual cracking.
Many manufacturers guarantee up to 90% of the panel’s efficiency target (e.g., 90% of 20%) over the first 10-15 years and 80% of its efficiency target over the last 10 years (e.g., 80% of 20%).
Again, don’t look at the output voltage and the efficiency of a panel under consideration in isolation. Instead, weigh it up against the solar panel life expectancy. The life expectancy and the power output correlate directly.
Panel voltage, battery voltage, and inverter voltage
Your panel’s voltage should correlate with the battery and the inverter. A solar charge controller regulates the voltage and current and prevents the batteries from overcharging.
A 12-volt solar panel giving a peak output of approximately 18 volts will be enough to charge a 12-volt battery (with the solar charge regulator regulating the voltage).
A power inverter converts the DC (direct current) power to regular household volt AC (alternating current), from which you can run most of your household appliances. With a step-up transformer, the AC volts convert up to 220-240 volts; alternatively, two inverters can be series-stacked to produce 220-240 volts.
Considering that everyone's requirements are different, the average electricity consumed per day is only a starting point to determine your specific solar power requirements.
In the example where you need 30,000 watts per day, with 5 hours of peak sunshine, you need to generate 6,000 watts per hour.
So on average, a home consuming 30,000 watts per day would need approximately 25,250W solar panels or 17,370W panels.
To figure out what you need in terms of solar panels, bear the following in mind:
- Energy consumption
- Weather (some panels fair better in hot or cold weather than others)
- Roof area
- Solar energy efficiency and solar panel lifespan
You should understand the voltage output of the solar panel and the context of the battery and inverter. Finally, the AC translates to household appliances.
The voltage output shouldn’t be seen in isolation as it directly relates to the current and the power.
The way solar panel output voltage relates to the electricity requirement of your home determines how many solar panels you need.
Did you find our blog helpful? Then consider checking:
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- Solar Panel Energy Transformation
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- How to Calculate Solar Panel Battery and Inverter
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