Updated on September 17, 2025
When do solar panels start producing electricity? When do they finish for the day? Does this matter when you’re choosing what type of solar energy system to install?
Yes, it does.
If you’re looking to maximise your solar system’s efficiency, you’ll need to consider startup voltage and how it affects your solar panel performance. This plays a role in whether you choose microinverters, string inverters, or even hybrid inverters, and it impacts how much solar power you generate across the day.
At PSC Energy, we understand that several technical terms pop up when you’re deciding what type of solar system to install. Some of those terms require math, some require science, and they can all be answered by licensed electricians (we have so many on our staff!). It’s a lot of information to take in, but we’re here to support you.
In this article, you will learn:
- What is Startup Voltage?
- How Does Startup Voltage Affect Microinverters and String Inverters?
- How Does Oversizing Improve Startup Voltage?
- FAQ: Startup Voltage
By the end of this article, you’ll understand what startup voltage is and how it affects your solar efficiency. You’ll be better informed and able to make some choices regarding your system based on that information.
What is Startup Voltage?
Startup voltage is easy to define. In the morning, the sun rises, and that sunshine reaches your solar panels. The panels need to receive a minimum amount of sunlight to create a current in the solar system, which will turn the inverter (or microinverter) on.
Every inverter has a minimum input voltage that it needs to receive from the solar panels to turn on. Without that minimum power input, the solar system won’t kick start.
As the sun rises, it shines more directly on your solar panels from above. When sunlight hits your panels at an angle, they are less efficient at harvesting that sunshine because the irradiation is diminished. But as it makes its way above our heads, it shines more powerfully on your panels.
Different inverters have different requirements to trigger their functionality. Microinverters will kick on earlier in the day with less sunlight shining on them. In contrast, string inverters need more sunlight from the panels to start functioning. Let’s get into it.
If you’re interested in learning more about solar systems, you might want to check out our introductory article titled, New to Solar: Start Here.
How Does Startup Voltage Affect Microinverters and String Inverters?
Current is the flow of electricity.
Power = Voltage x Current
In our other articles in the PSC Learning Centre, we talk about power in terms of watts and kilowatts. These are units of measurement for power. The above equation can also be written as such using their respective units of measurement:
Watts = Volts x Amps
These are just different vocabulary words for the same equation. Power is measured in watts, voltage is measured in volts, and current is measured in amps.
In order for this article about voltages to make sense, we need to use the correct language.
At dawn, there is sunshine, but as you’ve noticed, it’s not as strong as it is at midday. The panel will produce voltage from that sunlight that’s hitting it from low on the horizon, but it won’t be much. The amount of sunlight shining on those panels will increase throughout the day.
There won’t be any current (flow of electricity) until the inverter turns on. Electricity is like water; it will always follow the path of least resistance. It won’t flow anywhere if there isn’t a current.
With an Enphase microinverter system, the startup voltage is 22 volts. The solar panel needs to be outputting between 18 and 58 volts for the microinverter to wake up.
The microinverter will turn on automatically when 22 volts are detected from a 50-volt panel. Current will be created, and the system will perform beautifully.
String inverters have startup voltage requirements as well. For example, the Fronius 10kW SYMO has an operating window from 270 volts all the way up to 800 volts. The startup voltage, however, is 200 volts – ten times the amount of power needed to activate an Enphase microinverter.
The amount of electricity is now much higher than what a microinverter needs, but a string inverter has multiple panels outputting electricity to it. In contrast, a microinverter is mounted under each solar panel to perform the same function.
This next bit is going to get a little technical. There’s some math. Don’t worry, we’ll get through this.
The Fronius SYMO 10 (if it was designed and installed by a smart and forward-thinking installer) will be connected to somewhere between 11 and 13 panels. With that many panels collecting sunlight early in the morning, the Fronius SYMO 10 will actually turn on around the same time as an Enphase microinverter. And theoretically, they should both turn off around the same time in the afternoon.
However, if your installer has connected a Fronius 10kW SYMO to a string of panels that’s ten panels or less, in that case, there’s no way the inverter will turn on earlier than an individual microinverter with a single panel. Why is that?
If there are five panels connected on the string, those five panels will receive 50 volts each for a total of 250 volts on that string. When that inverter kicks on depends on when those panels will each receive 50 volts from the sun, combined to output a total of 250 volts. A single Enphase microinverter only needs 22 volts. It has a significantly lower startup voltage.
The better or bigger your solar system is oversized, the less those panels will have to work in the morning to turn on your inverter (or microinverter). Once your inverters are turned on, current will become present, and then that voltage multiplied by current equals power.
The inverter will start producing power for the home once there’s enough sunlight to make that equation happen. That inverter (needs to switch on as early as possible in the morning if you’re looking to maximise your solar system’s efficiency.
A microinverter will switch on earlier in the morning than a string inverter. The same is true for shutdown; the string inverter will switch off and stop operating once the sunlight dims and the panels can’t produce the minimum amount of voltage to the inverter. Microinverters that need less sunlight to output voltage will produce energy later in the day than a string inverter system.
You will get better performance from your system in the early morning and evening with an Enphase system because of the technology’s sensitivity to sunlight.
If you’re interested in learning a bit more about how microinverters compare to string inverters, you might want to check out the following article titled, Microinverters vs. String Inverters: An Honest Comparison.
How Does Oversizing Improve Startup Voltage?
The solar panel converts sunlight into direct current (DC) power. The inverter (or microinverter) converts the DC power into AC (alternating current) power.
At PSC Energy, we install Enphase IQ8HC Microinverters that have a peak power output rating of 384W (that’s the maximum amount of DC power it can convert to AC power), and Trina Vertex S+ solar panels with a maximum power output of 440W (this collects the DC power that’s fed to the microinverter for conversion to AC power).
How does this relate to startup voltage?
If those panels are receiving sunlight much earlier and later in the day, then they will create voltage that the microinverter (or inverter) will detect earlier and later. The system will switch on sooner and switch off later because the panels are feeding more power to the microinverter (or inverter) than if there were fewer panels on the roof.
Because the panels can harness more sunlight than the microinverter can convert, they can send volts to the microinverter (or inverter) earlier and later in the day.
Try to think of it this way: the overall kWh generated throughout the day will be increased because the solar production window is longer.
If you’re interested in learning a bit more about oversizing, you might want to check out the following article titled, Oversizing Your Solar Panel System: How to Maximise Your Panels for Bigger Returns.
Sunrise, Sunset: Wrapping Things Up
Now that you understand the importance of startup voltages, you’ll be closer to making some decisions about your solar system and whether it can meet your needs.
A microinverter solar system will kick on earlier in the day and continue working until later in the evening because it needs less sunlight to generate current than a string inverter solar system requires.
At PSC Energy, we work with you to build a solar system that will maximise your investment in clean energy and reduce your dependence on the electric grid. The choices you make with your installation will save you money in the long run.
If you’re interested in learning a bit more about solar panels and energy systems, you might want to check out the following article titled, Are Solar Panels Worth It in NSW, Australia? A Price Breakdown for 2025.
FAQ: Startup Voltage
What is startup voltage for solar panels?
Startup voltage is the minimum voltage your inverter needs to turn on and start making usable power.
Why does solar inverter startup voltage matter?
Lower startup voltage means your system wakes earlier in the morning and keeps running later in the afternoon. That longer “solar day” adds kWh and shortens payback.
When do solar panels start producing each day?
Panels make a little voltage at first light. As the sun rises, voltage climbs. Once the inverter sees its startup voltage, it turns on and power flows to the home.
When do solar panels stop for the day?
At dusk, sunlight drops. Voltage falls below the inverter’s minimum. The inverter shuts down and production stops.
How do volts, amps, and watts relate to startup voltage for solar inverters?
Watts = Volts × Amps.
Volts are electrical “push.” Amps are electrical “flow.” Watts are usable power.
What startup voltage do Enphase microinverters need?
Enphase microinverters wake at about 22 volts. They work with panel outputs roughly 18–58 volts.
What about a common string inverter example of startup voltage?
A Fronius SYMO 10 kW has a startup voltage ~200 V and an operating window of about 270–800 V. It needs the string to reach those levels before it turns on.
Why is the microinverter start up voltage earlier then that for string systems?
Each panel has its own microinverter that needs only ~22 V. That is much easier to reach at dawn than the 200 V+ a string inverter needs across a whole panel string.
Can a well-designed string system still start early?
Yes. If you size strings smartly (often ~11–13 panels per string on a SYMO 10), the combined voltage rises fast enough that wake-up can be close to a microinverter system in many conditions.
What is “oversizing” and why does it help with solar panels?
Oversizing means pairing more panel wattage than the inverter’s continuous AC rating. More panel area gathers more light at the edges of the day. That raises voltage earlier and keeps it up later, so the inverter switches on sooner and off later.
Does oversizing solar panels damage equipment?
No, when designed within the manufacturer’s limits. The inverter simply clips brief peaks. You gain kWh over the full day because the production window is longer.
Which gives better dawn/dusk performance: microinverters or string inverters?
All else equal, microinverters. They need much less voltage to wake and to keep running.
Can string systems match that with design tweaks?
They can get close with the right string length, clean wiring, and good orientation. But they still need a much higher minimum voltage to start.
How do roof pitch and direction affect startup voltage?
Shallow pitch and east/west faces see usable sun earlier and later. Steeper pitch and south faces need stronger sun to hit startup and will start later in winter.
Will adding “more panels” help my solar panel system start earlier?
Often yes. More panels = more light captured at low sun angles = higher early voltage. That helps both micro and string systems.
