Installing solar panels within 30 feet of batteries reduces some of the power loss that results when electricity moves from one point to another. A solar panel system can lose up to 24% of the electricity it produces. Some of the loss is unavoidable as the conversion of light into energy in a solar panel is not 100% efficient. However, losses from bad solar system design can be avoided with little due diligence.
There will always be some degree of energy loss in any electrical system. In the U.S, 5% of electricity is lost in transmission between the power plant and your home. This you have no control over. With a solar panel system, however, you have more say.
In this article, we will show you a few optimizations you can make to reduce your losses and make your solar energy system more efficient.
How Long Can Solar Panel Wires Be?
There is no maximum specified length for solar panel wires. There is, however, a maximum recommended length of 500 feet (152 meters). The longer the wire used in a solar system, the more inefficient, expensive, and complicated the system becomes. It is therefore advisable to keep wire connections between components in a solar energy system as short as possible.
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Moving electricity over longer distances from where it’s generated to where it is used increases the cost and decreases the available amount of electricity. This applies as much to the U.S electricity grid as it does to your solar panel system.
It’s not that much different from pumping water from a well to a tap. The longer the distance between the well and the tap, the more water will be lost and the more pipe you need, which increases your expenses.
With electricity, the concept that makes electricity inefficient to move over long distances is known as voltage drop.
How voltage drop affects solar system design
Voltage drop is the loss in power between the source, which in this case are solar panels, and the load, which are batteries or your appliances.
An electrical conductor or the wires in a circuit experience resistance or impedance to the flow of current. The less resistance in a circuit, the more current flows through it. However, you cannot have a total absence of resistance, there will always be a minimum resistance.
Resistance in a solar system can be measured as the difference in voltage between the solar panels and the load. Subtracting the voltage at the load from the voltage at the solar panels will give you the voltage drop or the resistance in your system.
Voltage drop is unavoidable but it can be reduced. Voltage drop is affected by cable thickness and length. To reduce voltage drop in a system to an acceptable level, you need to select a cable of the right thickness and keep the length of your cables as short as possible.
The longer your cable runs, the thicker you will have to make it to make up for the voltage drop. This will add to your expenses and the complexity of your design. A shorter run is cheaper and simpler to execute.
The National Electrical Code (NEC), recommends the maximum voltage drop in your system should not exceed 3%. Source
How far should solar panels be from your house?
It’s generally recommended that the distance between your solar panels and your load, whether that be your batteries or inverters, not exceed 30 meters.
For more on this, check out our post “How Far Can Solar Panels Be From An Inverter? Why It Should Be Close-by!” & “How Far Can Solar Panels Be From A House? Why It Shouldn’t Be Too Far!“
How Far Can Charge Controller Be From Batteries?
Charge controllers should be no more than 3 feet (1 meter) from a battery bank. It is preferable to have a charge controller in the same room as the batteries it is connected to. Having the components closer together improves the efficiency of a solar system and reduces the cost of designing it.
As with the distance between solar panels and your home, inefficiency as a result of power loss in transmission increases with longer connections. It’s also much simpler to monitor, troubleshoot and maintain the components of your solar system when they are closer together.
Charge controllers give you readings of the state of your batteries. It is thus more convenient to have them closer to your batteries especially when you’re troubleshooting a faulty battery. Source
How Far Can You Run 10 Gauge Solar Wire?
The National Electrical Code (NEC), gives the maximum distance to run a 10-gauge wire at 85 feet or 26 meters. This is for carrying 120 volts at 20 amperes. For a 15-ampere circuit, the distance can be increased to 115 feet or 35 meters.
The danger with longer runs of wire is in the resistance. Longer runs will have a larger voltage drop. Voltage drop is resistance to current flow. Resistance can lead to heat build-up which can damage circuits, components in a solar system, and of course any load attached to the system. There is also a small risk of fire. Source
Solar panels of over 50 watts mostly use 10-gauge wire as this allows a current of 30 amps to flow through. 30 amps are what most home appliances like dryers and air conditioners use.
The smaller the gauge, the thicker the wire. Smaller gauges allow more current to flow through. A 1/0-gauge wire for example has a current of 150 amps. This is because there is less resistance in the thicker wire. This is what is used to connect batteries in a battery bank.
Where Does Solar Go When Batteries Are Full?
Once the batteries are fully charged, energy is sent to the inverter. The inverter converts the DC energy from the battery into AC before it can be used in the home. Any excess energy that is not used in the home is exported to the grid in a grid-tied system. In an off-grid system, the energy is wasted if there is no consumption.
Electricity is either stored, used, or exported. With a grid-tie system, you can benefit from the excess energy your system does not store or you do not use through net metering. This is when you send the electricity you don’t use into the grid and receive credits in return. Source
We also highly recommend that you check out our post “What Happens If A Solar Panel Is Not Connected To Anything? What To Do!“