High Voltage vs. Low Voltage Off-Grid Solar Solutions For Residential Use
TL; DR: We prefer low voltage off-grid solar systems for various reasons, including costs, ease of maintenance, and, most importantly, safety.
In fact, safety (i.e., minimizing fire risks and electric shock hazards) is so critical in a fire country like Caliente that we’re going to digress slightly before comparing the pros and cons of high and low-voltage systems.
Direct current (DC) requires a much more rigorous approach to safety than alternating current (AC)
AC is what comes out of the wall and powers appliances. In the US, the flow of electricity changes direction twice sixty times a second. When it does, no current comes out of the outlet for an extremely brief moment, making it less difficult to break contact. If you accidentally touch exposed, conductive parts, you have a shot at pulling back.
On the other hand, DC is continuous and can get gnarly. Even if you manage to break contact, you get an arc that’s thousands of degrees and doesn’t readily extinguish. They vaporize the conductors — feeding the plasma, lowering its impedance, and increasing the power the arc consumes — to create a thermal runaway effect. If you accidentally touch exposed, conductive parts, you don’t have a chance of pulling back.
If you think a butane torch can set things on fire fast, try a DC arc (sounds like some superhero move, doesn’t it?)
This is a DC arc. It can melt copper in seconds. Source.
Solar panels generate DC (an inverter turns it into AC before feeding into the electrical circuit), making safety even more critical in a solar solution. A lower voltage system offers an additional safety barrier against arc faults.
High-voltage vs. low-voltage solar systems
Some jurisdictions classify systems under 50V as low-voltage, while others set the limit at 100V. Since safety is our top priority, we stick with the 50V definition.
Low-voltage solar systems typically operate at 12V, 24V, or 48V and are mostly used in small-scale off-grid applications like RVs, boats, or residences. Meanwhile, high-voltage systems are 120V, 240V, or higher, often used in larger setups (e.g., industrial and manufacturing).
How you wire the panels matters, too
When you wire solar panels in series, the voltage increases while the current stays the same (e.g., two 12V, 10A solar panels wired in series produce 24V at 10A). The higher voltage means you may use thinner wires (i.e., lower cost), but a failure in one panel can shut down the entire string (i.e., less resilient).
When you wire panels in parallel, the voltage remains the same, but the current increases (e.g., two 12V, 10A solar panels wired in parallel produce 12V at 20A). The higher current requires thicker wires, increasing the costs for long runs. However, you get higher resiliency because a failure in one panel will only impact the performance of one string, not the entire array.
We often combine series and parallel configurations to get the best of both worlds and achieve the voltage and current to meet each client’s requirements.
Comparing high-voltage vs. low-voltage off-grid solar solutions
Efficiency
High-voltage systems are more efficient in transmitting energy over long distances due to less power loss (that’s why utility companies use high-voltage lines). However, the power loss is insignificant for compact setups (e.g., RV, cabins, and residential projects) with short wire runs.
Costs
High-voltage systems involve costlier components (e.g., inverters, charge controllers), but the lower current allows for thinner, cheaper wiring for large systems with long wire runs. Meanwhile, low-voltage systems use less costly components but require thicker cables, increasing the cost for long runs.
Safety
High-voltage systems pose higher risks of fire and electric shock and require extra precautions and specialized safety components, increasing the solution’s costs and complexity. While you should still take the proper safety measures for a low-voltage system, the parts are easier to maintain.
Resiliency
Most high-voltage systems wire solar panels in series to simplify installation. However, a failure in just one panel could take down the entire system (or a sizable part). Our low-voltage systems combine parallel and series wiring to increase resiliency while providing ample power output.
Scalability
Series wiring in high-voltage systems makes adding panels more complicated. On the other hand, the combination of series and parallel wiring in low-voltage setups makes it easier to scale up the system by incorporating more panels to boost production without overloading the system.
Battery
High-voltage batteries are more efficient for large-scale setups. But they’re costlier and pose more safety concerns. Low-voltage batteries are more suitable for residential use with lower energy requirements due to their safety profile.
Maintenance
High-voltage systems are more complex and dangerous, requiring specialized skills in troubleshooting and maintenance. On the other hand, it’s easier to perform basic maintenance tasks on low-voltage ones (e.g., cleaning and inspecting the equipment).
Maximize the benefits of low-voltage, off-grid solar systems
We recommend a low-voltage solution for most off-grid solar projects in Caliente. We do a few things to help our clients maximize the pros and minimize the cons of this approach:
We perform a site selection process to optimize solar yield and minimize wire runs while considering each property’s terrain and vegetation to ensure practicality.
We implement a modular, expandable design combining series and parallel configurations to ensure scalability and increase resiliency — you can easily add capacity without overhauling your system or experiencing extended downtime.
We don’t skimp on safety measures. We do cowboy things here (literally and figuratively), but not with anything involving electricity.
Have your cake and eat it too: Get in touch to see how we can help you design and implement a safe, efficient, scalable, and resilient off-grid solar system to meet your power needs.
