How Many Solar Panels Can Your Inverter Take? Matching Panels to Hybrid and All-in-One Inverters
How many panels an inverter can take depends on three numbers on its specification sheet, not on its wattage: the maximum PV open-circuit voltage (Voc), the MPPT voltage window and the maximum PV input power. For our 24V all-in-one units, the STS20224 and STS30224, that means up to 1,600W of panels in strings of one or two, kept under 100V. The 48V STS50248 takes up to 4,400W in strings of two or three, under 145V. The STM 8200W and 10200W hybrids take one long string under 500V, around nine 550W panels on typical label figures.
The three numbers that decide it
Open-circuit voltage (Voc)
Voc is the voltage a panel produces in sunlight with nothing connected. Panels wired in series add their voltages, so a string of three panels has three times the Voc of one. The string's Voc must stay below the inverter's maximum PV open-circuit voltage at all times.
The MPPT window
The MPPT charger hunts for the voltage at which the array gives its most power, and it can only do that inside its stated tracking range. Panels have a lower working voltage (usually written Vmp on the label) than their Voc, and it is the string's Vmp that needs to sit inside the MPPT window.
Maximum PV input power
The most array wattage the charger is rated to accept.
The cold-morning margin
As general guidance, a panel's Voc rises as it gets colder, so a string is at its highest voltage on a clear, cool morning, the kind highland sites in Kenya see often. A common rule of thumb among installers is to keep the string's label Voc at least 10 per cent below the inverter's maximum.
What each inverter accepts
| Inverter | Battery | Max PV Voc | MPPT range | Max PV input | Price |
|---|---|---|---|---|---|
| STS20224 2000W | 24V | 100V | 30 to 85V | 1,600W | KSh 62,000 |
| STS30224 3000W | 24V | 100V | 30 to 85V | 1,600W | KSh 69,000 |
| STS50248 5000W | 48V | 145V | 60 to 115V | 4,400W | KSh 116,000 |
| STM82248 8200W hybrid | 48V | 500V | 90 to 450V (full load 360 to 450V) | Not published, check the data sheet | KSh 140,000 |
| STM102248 10200W hybrid | 48V | 500V | 90 to 450V (full load 360 to 450V) | Not published, check the data sheet | KSh 170,000 |
Note that the 2000W and 3000W STS units share the same 1,600W PV limit: the larger one gives you more inverter output, not more solar input. Both STM hybrids have a single MPPT tracker with a maximum input current of 27A and a maximum PV charging current of 160A.
Our two STN hybrids, the 12V STN16212 2000VA/1600W (KSh 52,000) and the 24V STN30224 3200VA/3000W (KSh 57,000), have built-in MPPT charging, but their listings publish no PV voltage or power limits. Check the data sheet before designing an array for either.
The panels in the examples
Our panel listings do not publish Voc or Vmp, so the examples below use illustrative figures only. Real values vary between panel models of the same wattage, so redo the sums with the label figures of the panels you buy.
| Panel | Price | Voc used (illustrative, check the module label) | Vmp used (illustrative, check the module label) |
|---|---|---|---|
| 350W panel | KSh 18,200 | about 41V | about 34V |
| 550W panel | KSh 28,600 | about 49.5V | about 41.5V |
We also stock a 420W panel (KSh 18,480) and a 485W panel (KSh 21,340); the same method applies once you have their label figures.
Worked examples
STS20224 or STS30224 (24V): small, low-voltage arrays
- 350W panels, two in series: string Voc about 82V, 18 per cent under the 100V limit; Vmp about 68V, inside 30 to 85V. Two such strings in parallel give 4 panels and 1,400W, under the 1,600W cap.
- 550W panels, one per string: Voc about 49.5V, Vmp about 41.5V, both fine. Two in parallel give 1,100W; a third would take you to 1,650W, over the cap.
- Not this: two 550W panels in series. At about 99V the string sits right on the 100V limit with no cold-morning margin.
STS50248 (48V): up to 4,400W
- 550W panels, two in series: string Voc about 99V, well under 145V; Vmp about 83V, inside 60 to 115V. Four such strings in parallel give 8 panels and 4,400W, exactly the stated maximum.
- 350W panels, three in series: string Voc about 123V, 15 per cent under 145V; Vmp about 102V, inside the window. Four strings give 12 panels and 4,200W.
- Not this: three 550W panels in series, at about 148.5V, which is over the 145V limit.
STM 8200W or 10200W hybrid (48V): one long string
- 550W panels, nine in series: string Vmp about 374V, inside the 360 to 450V full-load band; Voc about 445.5V, 11 per cent under 500V. That is 4,950W on one string.
- Not this: ten in series, at about 495V Voc, which leaves almost no cold-morning margin.
Before adding a second string in parallel on an STM, check the panels' short-circuit current on the label against the 27A input limit, and check the data sheet for the maximum PV input power, which the listings do not give.
Why the two families suit different jobs
The STS units work at low PV voltage, so each string is only one to three panels and a bigger array means more strings in parallel. That suits a small roof, a shop or a home with a handful of panels and a 24V or 48V battery bank. The STM hybrids want a few hundred volts from one string, which suits a larger roof where nine or more big panels fit in a row. Their listings cover hybrid, on-grid and off-grid installations, with a stated grid feed-in range of 195 to 253VAC, so they suit larger sites where solar, grid and batteries work together. For help choosing inverter output in the first place, see what size inverter a house needs.
Leave the final design to an installer
Final string sizing, DC cable sizes, fusing, isolators and earthing belong to a qualified solar installer working from the actual panel labels and the inverter data sheet.
Where to buy
Browse our solar inverters and solar panels, and compare panel prices in our solar panel price guide. Collect from our Nairobi trade counter at Royal Business Park, opposite Complast, Old Mombasa Road, Monday to Saturday, 8:00 to 17:30, with free pickup, or order for countrywide delivery at a flat KSh 350, free on orders over KSh 15,000. Installers and contractors can request a trade quote on our trade page. To check a panel and inverter pairing before you order, message us on WhatsApp.
Common questions
How many solar panels do I need for a 3000W inverter?
On the STS30224, the PV input is limited to 1,600W, so in the examples above that is four 350W panels (two strings of two) or two 550W panels in parallel. For the STN30224 3000W hybrid, the listing does not publish PV limits, so check the data sheet.
How many panels for a 5kW inverter?
The STS50248 accepts up to 4,400W of PV: for example eight 550W panels as four strings of two, or twelve 350W panels as four strings of three, with Voc kept under 145V.
Can I connect a 550W panel to a 24V inverter?
Yes, to the STS20224 or STS30224, one panel per string, because the MPPT charger converts panel voltage to battery voltage. Do not put two in series on these units: at the illustrative 49.5V each, the string comes to about 99V, right on the 100V limit with no margin.
Series or parallel?
Series raises voltage, parallel raises current. Wire in series until the string Vmp is inside the MPPT window and the Voc keeps a safe margin under the maximum, then add strings in parallel up to the power and current limits. For whether you need an inverter at all, see solar home system or inverter.