Solar panels are made up of tiny solar cells, each generating 0.5V wired together in series to boost the total solar panel voltage. The solar panel output voltage is determined by the number of solar cells wired together into a single panel.
High voltage solar panels are more efficient than low voltage panels and require less space to deploy thus reducing the cost of materials and labor to mount them on a roof or ground mount. High voltage panels require thinner copper wire to connect the array, the charge controller, and the battery bank.
The most available solar panel size is a 60-cell panel with a nominal voltage output of 20V. Ideal for grid-tied solar, a total of twelve panels in series will be below the grid-feed threshold of 600V. The solar panel voltage provides the “electron pressure” to feed the power into the grid.
The solar panels designed for off-grid solar systems are manufactured with the following voltage outputs:
- 36 cell panel delivering 18V is ideal for charging 12V battery banks
- 72 cell panel producing 36V is perfect for charging 24V battery banks
- 60 cell panel producing 20V is used for grid-tied solar
The higher the system voltage, the more efficient the system will be and cost less per kWh delivered. Let’s look at how the system voltage selected can impact the type and cost of components in the solar power system.
What System Voltage Is The Best To Install For Your Solar System?
Choosing the best system voltage for your off-grid solar power systems always remember that bigger is better. A 48V system is the most efficient and will cost the least per Watt-hour delivered compared to 24V and 12V systems.
Small 12V systems are ideal for automotive applications such as RVs, vans, and campers. They are easy to install, and the components are readily available. Automotive lead-acid batteries or deep cycle marine batteries are ideal for keeping costs down.
Unfortunately, a low voltage system means that the current amperage needs to be higher to deliver the required Watt output to power appliances and devices. Remember that Voltage times Amperage equals Watt output.
Lower voltage systems require thicker copper cables to cope with the additional current strength. Copper is expensive and adds significantly to the system costs.
The battery charge controllers and inverters are also less efficient at low voltages, and they have their internal resistance to overcome.
Using a 24V Solar System
Deploying 24V systems is already much better for energy efficiency and lower costs due to thinner copper cables and more efficient inverters and charge controllers.
The other advantage is that 12V solar panels can be wired in series to boost the voltage to 24V. Strings of 12V solar panels in series can be combined in parallel to increase the current strength.
24V systems are ideal for tiny homes or larger RVs and are compatible with military standard equipment.
Using a 48V System
Most large homes or industrial workshop operations will require a 48V system. The one downside of 48V systems is that they can pack enough power to cause fatal shock or start an electrical fire.
These systems are not for DIY enthusiasts that are novices with solar-powered electrical systems. A 48V solar array can be set up by wiring four x 12V solar panels in series, thus producing sufficient open current voltage to charge a 48V battery bank.
- Electrical components and circuits perform better at higher voltage and lower current.
Conducting electricity over long distances is done via high-voltage power lines as this is the most efficient method resulting in the lowest energy transfer losses. The same principle applies to a solar power system.
MPPT Charge Controllers and Inverters
MPPT charge controllers and Inverters designed for 48V systems are more efficient and cost-effective in getting the high voltage DC into your battery bank or converted to AC for powering the loads in your house.
The components for 48V systems are not readily available from local solar and electrical supply stores but are freely available for online ordering and delivery. You may need some 40 Amp converters to step the voltage down for DC devices, but these do not cost a lot of money.
The Pros and Cons Of 12V / 24V / 48V Solar Panels
| 12V Pros: | 12V Cons: |
| Ideal for small systems in RVs and Vans Suitable for charging 12V car batteries and 12V battery banks Solar panels are widely available in a range from small to large Watt outputs: 10W, 20W, 40W, 50W, 125W, 160W and 180W | It takes up a lot of roof space or large ground mount and Cannot be far away from the charge controller and battery bank due to voltage loss It will require thick gauge copper wiring to handle high amperage |
| 24V Pros: | 24V Cons: |
| Ideal for large cabins or RVs Suitable for charging 24V battery banks Solar panels available in 330W and 350W Light enough for one person to handle on the rooftop It takes less space on the roof, and ground mounts Inverter and solar charge controllers for 24V systems are less expensive per Watt output Inverter and solar charge controllers for 24V systems are more efficient than 12V components per Watt output Required thinner gauge wire due to higher Voltage and lower Amperage Used the same labor as a 12V system to install Ideal for large cabins or RV | Less widely available than 12V panels and system components |
| 48V Pros: | 48V Cons: |
| Ideal for powering off-grid homes, workshops, and electric vehicles Suitable for charging 48V battery banks Lowest cost per kWh produced All-in-one Inverter/Chargers are widely available | Solar panels not widely available due to size Difficult to handle on sloped rooftop Requires qualified expert installation due to risks of electrocution and fire. |
| 30V Pros: | 30V Cons: |
| Ideal for grid-tied systems 13 x 30V panels fall within the 600V maximum grid input Highest volume demand results in the best price per Watt of any solar panel size MPPT solar charge controller can adjust voltage and output to optimal battery charging in off-grid systems | Requires more expensive MPPT charge controller to adjust voltage and amperage to 12V or 24V battery bank Requires installation and approval by a registered qualified electrician |
For novice DIY solar power enthusiasts, a small 12V system will be the recommended size system to install and learn about solar power in a relatively safe and inexpensive way.
- Charging up your 12V batteries for the RV, boat, or vehicle is a good application.
For more efficient and cost-effective off-grid applications such as a yacht, RV, or tiny home, a 24V solar panel array, solar charge controller, inverter, and battery bank is recommended. The system components are more expensive than 12V components but will yield a lower cost per kWh produced.
Off-Grid Voltage
Suppose you plan to have complete energy independence from the grid and need to run your entire household and potentially charge your EV. In that case, a 48V solar panels array, Inverter-Charger, and battery bank are recommended.
All-in-one 48V Inverter Chargers are very cost-effective and efficient, and two units can be wired in parallel to provide 240V phased AC output.
A qualified technician should install these systems as they pack enough power to cause a lethal jolt or cause an electrical fire.
