The amount of energy your solar panel produces depends on two factors: how much sunlight it gets and how many amps your solar panel generates. The more watts a solar panel generates, the more money you’ll save on your electricity bill.
If you have a roof that gets lots of direct sunlight, you can use less expensive, lower-wattage solar panels. Solar panels with higher wattage produce more electricity per square foot and cost more upfront but will save you money over the long term.
The amp rating tells you how much power your solar panel will generate under optimal conditions. An amp is an international unit of power; 1 amp is equal to 1 ampere (A). A photovoltaic (PV) system generates electricity when photons from the sun strike semiconductors in the panel and excite electrons inside them to flow through wires and into a home or business’s electrical circuit.
PV systems use different numbers of strings called wafers, cells or modules to generate electricity, which fall into one of three categories: residential-scale (325 watts); commercial-scale (1 kilowatts); or utility-scale (20 MWs).
What’s the Difference Between W/W (Watt/Watt) and W/m²?
Every solar panel measures power in watts and has a letter or number following it to indicate the panel’s wattage. This letter or number indicates the panel’s W/W (power per unit area). For example, a 250 W solar panel has a W/W of 2.5 W/m². The W/W (or W/m²) is usually higher than the W/m² because solar panels are usually measured in W/W. Power is measured in watts (W) and watts per meter squared (W/m²).
A common question we get from our customers is whether it’s better to have a solar panel with a higher W/W or a smaller area. In general, a higher W/W solar panel will produce more power, but the panel will cover a smaller area.
Amperage for Solar Panels
PV panels come with a certain number of amps (A). The higher the amps, the more power the solar panel will produce, and the lower the voltage will be in your home’s wiring. Of course, you want your solar panel’s voltage to be as low as possible without impacting how much power it produces.
If your solar panel has a lower-than-expected wattage, you can upgrade to a higher-amp model to boost production. A panel’s amps are usually labeled at the bottom. It’s common to see solar panels with 50, 60, 80, or 100 amps.
How to Calculate Solar Panel Amperage Requirements
If you have a PV system with W/m² solar panels, you’ll need to calculate the amp draw for your PV array. You can usually do this with an online PV system calculator. First, divide the panel’s W/m² by the panel’s nominal voltage, which is usually 108 or 120 volts. Be sure to round up to the next whole number.
Next, multiply the result by the PV array’s nominal current. This is the amount of power the PV array will draw from your electrical circuit at full power. It’s important to calculate the voltages and amperages carefully so that they don’t cause your home or business to overheat. Overheating can damage your PV system components and could even cause fire.
The Importance of Voltage in a PV System
There are three important voltages in a PV system: solar panel voltage, inverter voltage, and utility voltage. Solar panel voltage: This is the voltage the solar panel itself produces. PV panels come in varying wattage options, and you’ll want to make sure the voltage of your solar panel is compatible with your home’s electrical wiring. Inverter voltage: This is the voltage at which your PV system sends power to your electric utility’s system.
Your inverter needs to have a voltage of at least 108 volts, but it’s best to have a lower utility voltage, which is usually between 88 and 97 volts.
Utility voltage: This is the voltage your home and all its appliances will use. If you live in an area with higher-than-average electricity costs, you’ll want your solar system to run at a low voltage. Solar panels can be configured to run at 12 volts, which means they’re able to run off of small batteries.
There are many types of solar panels available, and you’ll likely want to experiment with different models to find one that works best for your specific roof and location. You can also choose a solar panel with a higher W/W rating.
A higher W/W solar panel will produce more electricity but cover a smaller area on your roof, saving you money and helping the environment.
When you install a solar panel system, be sure to calculate the amp draw for your PV array and make sure it has the required voltages for your home. You can learn more about how to calculate your solar panel system’s voltage and amperage draw by reading our blog post, How to Calculate Voltage and Amperage Draw in a Solar System.