Solar Panels vs. Batteries vs. Power Supplies: What You Need to Know

Whether you're building a remote monitoring system, powering mobile electronics, or designing an off-grid solution, selecting the right power source is crucial. 

The three most common options are power supplies, batteries, and solar panels.

Understanding how these sources produce and deliver power can help you design a more reliable, efficient, and safe energy system.

In this post, we’ll break down how each one works, compare them, and discuss when to use one over the other or combine them for the best results.

Key Differences at a Glance

How Each Power Source Works

Power Supplies

Power supplies are designed to provide a constant voltage, regardless of the connected device's activity (within design limits). The USB wall adapter you use to charge your phone is a typical example. That’s a regulated power supply.

Since power supplies are typically connected to the electrical grid or another stable energy source, they can deliver steady and predictable power over extended periods of time. This makes them ideal for applications where voltage stability and reliability are critical, such as lab equipment, household devices, or fixed installations.

However, power supplies are only available where grid access or another consistent source of electricity is present. In remote or mobile environments, they aren’t practical without backup systems.

Batteries

Batteries store energy and release it as needed. As you draw current from a battery, the voltage gradually drops, especially under heavier loads.

Figure 1. Discharge curve of a lithium-ion battery, illustrating how voltage declines gradually with increasing capacity. Even after delivering its full rated capacity, the battery retains some voltage, highlighting the importance of proper discharge limits for performance and safety.

The rate of voltage decline depends on:

• Battery chemistry: e.g., lithium-ion vs. lead-acid. Discover the benefits of selecting the ideal battery chemistry.
  
  
• Depth of discharge: how much of the battery’s capacity is used
  
  
• Internal resistance: how much a battery resists current flow internally
  
  

Batteries excel at delivering stable power for extended periods. They’re especially useful when paired with solar panels to store excess energy and power devices when sunlight isn’t available.

Solar Panels and the IV Curve

Unlike power supplies and batteries, solar panels don’t produce a fixed output. Instead, their behavior depends on two key factors:

• The amount of sunlight hitting the panel
  
  
• The resistance of the device they’re powering

Solar panels follow a specific pattern, known as the IV curve (current vs. voltage), which defines the amount of current the panel supplies at various voltages.

Figure 2. IV curve comparing a 10 W solar panel and a 10 W USB power supply. The green diamond marks the panel’s maximum power point, where it delivers its peak output.

The IV curve includes three key points:

• Short Circuit Current (Isc) – the current the panel produces when the voltage is zero
  
  
• Open Circuit Voltage (Voc) – the voltage produced when no current is flowing
  
  
• Maximum Power Point (MPP) – the optimal balance of voltage and current, where the panel generates the most power

Panel efficiency varies by material and technology, which affects overall performance and power output. Learn how efficiency affects your setup.

The shape of the curve shifts depending on sunlight, temperature, and the materials used. As load resistance changes, the panel’s operating point moves along the curve.

Figure 3. IV curves showing solar panel performance under varying light conditions, measured in lux (a unit that quantifies visible light intensity). As light levels increase, the current output rises proportionally, while voltage stabilizes near its rated level. This demonstrates how panel behavior shifts in response to environmental changes.

Some panel designs perform more consistently in shaded or variable light. Single-cell solar panels are a great example of this innovation.

For example, if a phone is connected directly to a solar panel and draws more current than the panel can supply, the voltage drops, power output collapses, and charging may stop.

That’s where MPPT (Maximum Power Point Tracking) becomes essential. MPPT systems help maintain the panel’s optimal operating point on the IV curve. Pairing the panel with a battery or capacitor also helps stabilize power delivery during periods of cloudy weather or inconsistent sunlight.

Matching Power Sources to Loads

Now that you’ve seen how power supplies, batteries, and solar panels behave individually, the next step is to understand how they interact with the devices (loads) they power.

Each power source responds differently to load resistance, which plays a significant role in how efficiently power is delivered. This is especially critical when working with solar panels, as improper load matching can significantly reduce performance or prevent charging altogether.

Let’s take a closer look at how load resistance affects performance, and how to manage it using tools like MPPT and PMICs.

Load Resistance and Operating Points

Every electrical device presents a certain amount of resistance to the power source. This resistance helps determine how much current is drawn and how much voltage remains across the load.

While power supplies are designed to maintain voltage regardless of the load (within limits), both batteries and, especially, solar panels are more sensitive to resistance.

In solar systems, the resistance of the load dictates where the panel operates along its IV curve:

• If the resistance is too low (due to a heavy load), the panel can’t maintain its voltage. The voltage drops, and the power output collapses.
  
  
• If the resistance is too high (a light load), the panel’s voltage rises, but current drops, again leading to low power output.

The sweet spot is the maximum power point—where the panel delivers its optimal combination of voltage and current. But without a system in place to control this interaction, many devices never reach it.

That’s why power point tracking and load matching are essential when designing a solar-powered system. They ensure the load and panel stay in sync, especially under varying sunlight conditions.

Power Management Solutions

To get reliable performance from a solar-powered system—especially when charging phones or running small electronics—you need more than just a panel. The panel must be matched to the load in real time.

That’s where power management systems come in.

Two standard options are:

• Power Management Integrated Circuits (PMICs) – Compact, efficient circuits that manage voltage conversion and load control for low-power devices.
  
  
• MPPT (Maximum Power Point Tracking) charge controllers – These optimize power harvesting from your panel by continuously adjusting to operate at the ideal point on the IV curve. Learn more about choosing the right charge controller.

These systems:

• Help keep the panel operating at its maximum power point
  
  
• Adjust for changing sunlight and load conditions
  
  
• Convert variable panel voltage into a stable, usable output for charging or storage

Without power management, solar panels can underperform or fail to charge devices entirely. Batteries may overcharge or discharge too deeply, resulting in unreliable devices.

Pairing the right solar panel with a battery and a controller ensures your system stays efficient, even as conditions change throughout the day.

Safety Considerations

Short Circuits

Batteries can be dangerous if shorted. A high-capacity lead-acid battery, for example, can deliver thousands of amps during a short. This is enough to melt wires, destroy devices, or start a fire.

Solar panels, on the other hand, are inherently safer. Their short-circuit current is limited by lighting conditions. A typical 110W panel might produce a maximum of 6A under full sun, and not much more even in the brightest conditions.

Open Circuit Voltage

Solar panels also behave differently when disconnected. They revert to their open circuit voltage, which can be 30–50% higher than their standard operating voltage. For example, a 12V-rated panel may show 18V or more when idle.

This high voltage can damage sensitive components or pose a shock risk, so ensure:

• Systems are rated to handle open circuit voltage

• Proper protections are in place

Real-World Applications

Here’s how these sources stack up in actual use:

• Solar Only: Good for low-power or daylight-only operations (e.g., environmental sensors).

• Battery Only: Great for backup or mobile devices with moderate runtime needs.

• Solar + Battery: Best of both worlds. Store power during the day and use it at night or in poor weather conditions.

Power Supply: Ideal for fixed installations with stable access to grid power.

Example: Powering a Security Camera with Solar

Imagine you’re setting up a security camera in a remote location using a 20W solar panel.

At first glance, it seems simple—your camera only draws about 6W. But there’s a catch.

• The camera requires a stable 12V input.
  
  
• When the panel output fluctuates due to clouds or shadows, the voltage drops.
  
  
• As the output falls, the camera may reboot, freeze, or shut off completely.

To solve this:

• Using a 12V charge controller with MPPT ensures the panel stays at its maximum power point.
  
  
• Adding an appropriately sized battery ensures constant power during periods of reduced sunlight and at night.
  
  
• The result: stable, continuous operation—even in less-than-perfect light.

This kind of setup is ideal for off-grid monitoring, construction sites, or wildlife observation—anywhere reliability matters and power isn't always predictable.

If you’re looking for plug-and-play solar kits for phones, tablets, or small electronics, check out our LightSaver portable solar charging solutions.

Fleet managers can also benefit from solar-battery systems. Read our guide to solar power for commercial trucks for real-world examples.

Choosing the Right Power Source

There’s no one-size-fits-all answer. Your decision depends on:

• Power needs: How much energy your devices require and for how long, measured in watts and runtime
  
  
• Environmental conditions: Whether the system will be used indoors, outdoors, in full sun, or low-light conditions
  
  
• Portability: Whether the system needs to be carried, mounted, or stay fixed in one location
  
  
• Voltage stability requirements: Whether your devices need consistent voltage to function correctly or can handle fluctuations

If you’re designing a system from scratch, make sure to review our step-by-step solar power budgeting guide to properly size your panel, battery, and power management components.

Final Takeaways

• Solar panels provide clean, portable power, but require careful load matching for efficiency.

• Batteries offer stable output, but need protection from over-discharge and short circuits.

• Power supplies are consistent and simple when grid power is available.

For optimal results, especially in off-grid or portable systems, use a combination of solar and battery power with proper regulation and safety features in place.

Need help choosing the correct solar setup or have questions about integration? 

Reach out! We’re here to help you build a smarter, safer power system.