Solar Panel Maximum Voltage Calculator – Why it’s important
Snow covered solar panels – not a problem on the Gold Coast however it’s important to know that the lower the solar panel temperature, the higher the voltage the panels are producing.
With a solar power system it’s very important that the solar panels match the electrical characteristics of the solar inverter or charge controller that they’re connected to. So how do we work this out and what do you need to know? They’re good questions and this is where our solar panel maximum voltage calculator comes in handy! One of the electrical characteristics that are very important is the maximum voltage the solar inverter or controller can handle. That’s because if the voltage supplied from the solar panels is too high it won’t work and could be irreparably damaged.
Australian Standards PV array voltage requirements
Another important point is raised in the Australian Standard AS5033-2014 clause 3.1 which states the following:
“PV arrays for installation on domestic dwellings shall not have PV array maximum voltages greater than 600V. For non-domestic installations where the PV array maximum voltage exceeds 600V, the entire PV array and associated wiring and protection shall have restricted access.”
With these points to consider it’s very important that we know the maximum voltage of the solar power system. Luckily we have our solar panel maximum voltage calculator to help!
Note: This page deals specifically with the maximum voltages a solar power system will produce. Check out our solar panel voltage calculator page here for a calculator that covers both high and low solar panel voltage calculations.
Solar Panel Maximum Voltage – How to work it out
Working out the maximum voltage that your solar power system will reach is not a straightforward calculation. It’ll require information from the solar panel datasheet and some site-specific information to be entered into our solar panel maximum voltage calculator to calculate the maximum voltage the system will see. We need to take into consideration these 3 factors:
- The number of solar panels connected in a series string
- The minimum temperature found at the site
- The characteristics of the solar panels being used.
Let’s have a look at the information we require for our solar panel maximum voltage calculator, what it means and where you can get the information from.
Solar Panel Maximum Voltage Calculator – Information you need to know
REC 290W solar panel data sheet with information highlighted that’s required for voltage calculations – click for full size image.
Solar panel Voc at STC
This is the open-circuit voltage the solar panel will produce at STC, or Standard Test Conditions. STC conditions are the electrical characteristics of the solar panel at an airmass of AM1.5, irradiance of 1000W/m2, and cell temperature of 25oC. This information can be found from the solar panel manufacturers’ datasheet, please see an example here.
Solar panel temperature coefficient of Voc
The voltage that solar panels work at depends on the cell temperature. The higher the temperature the lower the voltage the solar panel will produce and vise versa. The voltage of the system will always be at its highest in the coldest conditions and the solar panel temperature coefficient of Voc is required to work this out. With mono and poly crystalline solar panels it’s always a negative %/oC figure, such as -0.30%/oC on the REC Twin Peak 2 290W solar panels. This information can be found on the solar panel manufacturers datasheet, please see an example here.
Minimum site temperature
This is very important and changes from site to site. As an example here on the Gold Coast near the beach, the lowest temperature is recorded as being 2.5oC by the Bureau of Meteorology. If you head up to Mount Tamborine in the hinterland the lowest temperature is recorded as dropping down to -1.1oC. To ensure the calculations are correct please check out the weather statistics for your local area.
No. of solar panels in a series string
When solar panels are wired in series strings (that’s the positive of one panel connected to the negative of the next panel), the voltage of each panel is added together to give the total string voltage. It’s therefore important to know exactly how many solar panels you intend to wire in series.
Got it all? Great, let’s go!
When you have all the information above you are ready to use the following solar panel maximum voltage calculator. This will quickly show if your solar panel design will suit your requirements. Just overwrite the data which is in the calculator – this data is for the REC 290W Twin Peak 2 solar panel used as an example above.
Hi Simon. I have 24V, 3KVA Hybrid Inverter (Tech Geeks) and I will be buying 2 x 24V, 200Ah batteries for installation. I’m willing to buy the Solar panels but I dont know how many panels and of how many Watts should I buy. The specs on the booklet says: Charging current – 50A, Max PV Array Open circuit voltage – 80VDC, PV Range at operating voltage – 30 ” 32VDC, Standby power consumption – 2W. How many panels to buy and of how many wattts? Thanks
Hi Bill, thanks for the comment and great question, it’s not stupid at all! You have a great point, the coldest temperature is usually just before dawn, and you are correct, the sun isn’t shining before dawn so is that really accurate?
According to the rather conservative Australian standards we are supposed to use the minimum temperature for each site for our calculations. The thing is even if the coldest temperature was just after dawn the amount of light falling on the panel at that time of day is very low, so the voltage the panel sees is quite low as well. Saying all that you are quite correct, this formula is very conservative, for the Gold Coast 10 to 12 degrees could realistically be used. In our business we need to comply with the Australian Standards for solar installations, so we need to use this formula for our solar panel maximum voltage calculations.
Hi Jamie, when panels are wired in series you add the voltages of each panel together. If it’s wired in parallel then the voltages aren’t added up, the current is added up. So say you had 4 panels, with 40 Voc and 10A Isc ratings.
If all 4 were wired in a series string it would be 160 Voc at 10A Isc.
If all 4 were wired in parallel it would be 40 Voc and 40A Isc.
If you had 2 strings of 2 panels in series it would be 80 Voc and 20A Isc.
I hope that makes sense! Please note this is just an example with round figures, I recommend taking into consideration the lowest temperatures as well.
Just a question on your listed topic about temperatures and voltages please forgive my stupidity but the temperatures you’ve listed at the Gold Coast would be at 3am in winter when there’s no sun wouldn’t you need to get the coldest temperature at say 9am which I couldn’t imagine on the Gold Coast was ever below 12 or so degrees ?
Hi. what if your solar panels are wired in parallel? how would the calculation change?