What’s the Deal with Watts and Volts Anyways?

Solar installations are rated based on how much energy they produce. As you may remember from your high school education, energy is equal to the product of power and time. Power is equal to the product of voltage and current.

To know how much power a system produces, you need to know both the system voltage and the output current. If systems 1 and 2 both have the same output voltage, the system that produces the most power is the one that produces the most current for a given amount of sunlight.

Let’s look at two scenarios to help make sense of this. Let’s say system 1 operates at 100V and produces 1,000 watts and system 2 operates at 50V and produces 2,000 watts. Even though system 1 operates at a higher voltage, system 2 is the one that produces the most power. This means that system 2 will result in a reduced electric bill in a grid-tied solar system. In another scenario, systems 1 and 2 both have the same voltage of 100V. System 1 can output 1,000 watts, while system 2 can produce 2,000 watts. System 2 is going to produce the most energy, and will result in a larger reduction in your electric bill.

In short, you see that a higher voltage system doesn’t necessarily mean it’s the best option for you. In that first scenario the higher voltage system didn’t produce more power. In the second scenario, two systems with the same voltage had varying power outputs. In order to decide what is the best for you, you’ll have to look at the power output and your energy needs.

What Do Inverters Do and Why Do I Need Them?

Inverters serve as the gateway between the photovoltaic system and the devices and appliances drawing energy from your system. They turn the direct current (DC) output collected from your solar panels into alternating current (AC), which is the standard used by all commercial appliances. Like panels, inverters include a voltage and wattage rating.

What is the Best Voltage for a Solar System?

Panels and inverters typically come in either 12V, 24V, or 48V options. Most RV’s and boats typically use 12V battery banks, so people usually stick with 12V panels. Be sure to check the voltage of the battery bank to ensure it is compatible with your panels and the rest of the system, particularly your solar panels. 12 volt systems used to be the standard for homes, but today, many larger home systems are rated at 24v or 48v.

12v systems are good for many DIY solar scenarios, such as:
1. RVs/motorhomes/vans
2. Camper trailers
3. Small cabin or tiny home

RVs and motorhomes typically already have 12 volt batteries for lighting, hot water heater controls, AC/heating controls, and refrigerators. Therefore, it makes sense to use the voltage that already works for that system.

If your energy needs are around 1,000 to 5,000 watts, go for a 24 volt system.

If your energy needs are over 3,000 watts, go for a 48 volt system. Large off-grid houses often use 48V.

If you’re in the middle of those ranges, such as 3,000 watts, one advantage of using a higher voltage battery bank and inverter is that it may save you money in the long run because you need less charge controllers and can use thinner cables for the same amount of power.

Can I Use a 24v Inverter with a Single 12v Battery?

No, you can’t use a 24v inverter with a single 12v battery. In order to use a single 12v battery, it would be best to use a 12v inverter.

Can I Use a 12v Inverter with a 24v Battery Bank?

No, it’s best to match the voltage of the inverter with the voltage of the battery bank for the safety and lifespan of the batteries. So if you have a 24 volt battery bank, you should use a 24 volt inverter.

Is a 24v Inverter Better Than 12v?

Again, no. It depends on your energy needs and the size of your other components. What is crucial is making sure you properly size your system to determine what voltage and wattage is best for you. If you have a 24 volt battery bank, a 24 volt inverter is definitely best.

Conclusion

It’s important to consider your specific energy needs when it comes to deciding whether to use a 12, 24, or 48 volt system. In short, if your energy needs are over 3,000 watts, go for a 48 volt system. If your energy needs are around 1,000 to 5,000 watts, go for a 24 volt system. If you’re looking to build a smaller, DIY system for your RV, van, or tiny home, go for a 12 volt system. Don’t be fooled thinking 48 volt is best just because it is a higher rating. Like everything else in a solar installation, you need to consider your specific needs, the existing components, and the system at large.