- Introduction
- Voltage vs Current: The Basics
- Why Current Matters for Wiring
- Inverter Efficiency and Voltage
- System Design Benefits of Higher Voltage
- Conclusion
Introduction
I recently sat down with a new customer to talk about designing a solar system for his shop. This isn’t just any shop, it’s larger than most homes. It has three sections: two smaller sides and one massive middle bay where he can park a 45-foot trailer and run heavy equipment. One side is already used for vehicles, while the other side is still empty. His main request? Light the entire shop and add a few outlets here and there.
With 16-foot ceilings and such a large footprint, I had to make one point very clear: the voltage we choose will determine how efficient and scalable this system can be. Once the conduits and wiring are in place, we don’t want to end up fighting against unnecessary energy losses or oversized cables.
On top of that, we’re also limited in how much solar we can put on a 12-volt system. This customer wanted at least 3,000 watts of solar, and that alone makes 12 volts a poor choice. At that scale, a higher-voltage battery bank (24V or 48V) is the only way to keep things efficient, safe, and expandable.
When most people think about solar systems, they focus on the panels, the batteries, and the inverter. But there’s another factor that can make or break a system’s performance: the battery voltage. A higher system voltage doesn’t just affect the batteries, it shapes cable size, inverter efficiency, installation costs, and overall energy losses. Whether you’re building a cabin, upgrading an RV, or powering a large off-grid shop, understanding the relationship between voltage and current is key.
Voltage vs Current: The Basics
Electricity is power (watts), and power is always the product of voltage × current.
- If the voltage is low, the current must be high to deliver the same power.
- If the voltage is higher, the current is lower for the same power.
Example:
A 1,000-watt load at 12 volts = 83 amps.
That same 1,000-watt load at 48 volts = 21 amps.
Right away, you can see that higher voltage systems need far less current to do the same job.
Why Current Matters for Wiring
High current means big cables. Copper wire isn’t cheap, and the thicker the wire, the more it costs. It’s also heavier, harder to work with, and harder to terminate safely.
On top of that, high current increases voltage drop, wasted energy lost as heat in the wires. The higher the amps, the worse the problem.
One of the biggest limitations with 12-volt systems is how much solar you can actually connect to them. For example, with a 12-volt battery bank, a charge controller would probably be maxed out at around 1,000 watts of solar before it hits its current limit.
Yes, you can upgrade by adding multiple charge controllers, but that comes at a huge cost. On top of that, it’s less efficient. More controllers mean more complexity, more points of failure, and additional conversion losses. And because the system is still working at low DC voltage, the equipment has to move higher current, which creates extra heat and puts more stress on both the controllers and the inverter as it boosts voltage to 120V AC.
In the end, sticking with 12 volts at this scale doesn’t make sense financially or technically. It costs more, it wastes more power, and it shortens the lifespan of your equipment. Moving to 24 or 48 volts keeps the system efficient, scalable, and much more reliable in the long run.
Inverter Efficiency and Voltage
Here’s where it really clicks for people:
When your inverter takes 12 volts DC and turns it into 120 volts AC, the current on the DC side has to be about 10 times higher to deliver the same amount of power.
Take a simple LED light bulb as an example:
- On AC: A 120-volt LED bulb that draws 1 amp uses 120 watts.
- On DC at 12 volts: The inverter must draw 10 amps from the battery to run that bulb (120 ÷ 12 = 10).
That means if the bulb runs for an hour, your battery loses 10 amp-hours. Even though the light only uses 1 amp on the AC side, the 12V battery side has to deliver ten times as much current.
Now let’s compare with a 48-volt system:
- 120 watts ÷ 48 volts = 2.5 amps drawn from the battery.
Instead of losing 10 amp-hours per hour, you’re only losing 2.5 amp-hours. That’s less stress on the batteries, less heat in the cables, and more efficiency overall.
System Design Benefits of Higher Voltage
Choosing 24V or 48V battery banks comes with several real-world advantages:
- Smaller cable sizes → lower material cost and easier installs.
- Reduced energy losses → higher efficiency, longer runtimes.
- Better inverter performance → most inverters above 3,000 watts require 24V or 48V minimum.
- Future expansion → higher-voltage systems scale more easily to support larger solar arrays.
- Compatibility with modern lithium batteries → many are designed around 48V for best performance.
Conclusion
In the end, our conversation was short and simple. The reality of what’s needed quickly became clear, and once again, education is the key to a successful outcome for our customer.
Higher voltage isn’t always necessary, for small systems like boats, vans, and tiny cabins, a 12-volt setup is simple and practical. But once your system grows beyond a few hundred watts, the advantages of 24V or 48V become hard to ignore.
Smaller cables, lower costs, and higher efficiency all add up to a smarter, more professional solar system, one that will perform reliably and last longer.
IOTG SOLAR LTD 5 Critical Mistakes To Avoid Before Buying Solar.pdf
For individuals seeking consultation, education, or assistance in system designs related to grid-tie or off-grid solar applications, IOTG Solar stands ready to help. Our team is available to address questions, provide valuable insights, and offer support at every stage of the solar energy journey. Feel free to reach out to IOTG Solar anytime for expert assistance and comprehensive solutions tailored to your specific needs.
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