Solar Panel Wattage Guide: 100W to 600W+

What the wattage on a solar panel means

The STC rating

Every panel's headline wattage is its maximum power at Standard Test Conditions (STC): sunlight of 1,000W per square metre, a cell temperature of 25°C and a standard light spectrum (AM1.5). Jinko's Tiger Neo 605W to 630W datasheet defines it in exactly those terms, and the Cinco specification sheets use the same definition. STC lets you compare panels like for like. It is not a promise about your roof.

Bifacial panels, which collect some light from the back, can carry a second, higher figure. The same Jinko datasheet lists 668W to 696W "bifacial" ratings for its 605W to 630W panels, measured with extra light on the rear. Compare panels on the front STC rating unless your installer has designed for rear gain, such as on a raised ground mount. Read more on bifacial solar panels on South African roofs.

Why real output is lower

Two things pull output below the label:

• Less sunlight than the test. Most of the day, sunlight is weaker than 1,000W per square metre.
• Heat. Output falls as the cell heats up. The datasheet gives a temperature coefficient: -0.29% per °C for the Jinko panels above, -0.34% per °C for Canadian Solar's HiKu6 460W and -0.35% per °C for Cinco's 200W panel. As an illustration, a cell running at 60°C on a hot roof is 35°C above STC, so a -0.34% panel loses about 12% of its power from heat alone.

Some datasheets show this directly. Canadian Solar's 460W panel is rated at 345W at NMOT, its nominal operating condition with less sunlight and a hotter cell. That's 75% of the STC figure, on the same panel.

Wiring, inverter losses, dust and shade take a little more. That's why the yield figures below already allow for 14% system losses.

Common panel sizes and what they're for

Dimensions and efficiencies from the manufacturer datasheets or retailer specification pages linked in the sources, checked on 20 October 2026.

The pattern is clear: as wattage rises, panels get longer, wider and heavier. Efficiency rises too. The 100W panel produces about 148W per square metre of panel. The 605W to 630W panels manage about 224W to 233W per square metre. On a roof, that efficiency is what lets a modern array fit.

Above about 650W, modules are mostly made for commercial and utility arrays. None of the home retail listings we checked went higher than a 640W panel.

12V panels and the controller question

Small panels are built to charge 12V batteries. The Cinco 100W panel's maximum-power voltage is 18.0V at 5.56A, which leaves headroom to charge a 12V battery in heat and low light.

The controller matters. A basic PWM controller holds the panel near battery voltage, so the panel can't work at its 18V sweet spot. At a charging voltage of about 13.5V, that 100W panel delivers roughly 13.5V × 5.56A, or about 75W, at best. An MPPT controller converts the extra voltage into charging current and recovers most of the difference. That calculation is ours, from the datasheet figures.

Watch the voltage on 200W panels. Cinco's 200W panel runs at 33.55V, close to a home panel's voltage, so it suits a 24V battery or a 12V system with an MPPT controller, not a 12V PWM setup. Home panels in the 555W to 630W range run at about 40V each and are wired in series strings into a hybrid or grid-tied inverter. They aren't meant for a small 12V controller.

How much does each panel produce per day in South Africa?

We used PVGIS, the European Commission's solar model, to estimate daily output for north-facing panels at a 26° tilt (a common roof pitch) with 14% system losses. The same data runs our roof fit calculator, which works out panel count and output for your actual roof faces.

kWh per panel per day, year-round average with the June average in brackets. North-facing, 26° tilt, no shade. Source: PVGIS 5.2, checked on 20 October 2026.

620W panel2.98

555W panel2.66

460W panel2.21

100W panel0.48

Two practical notes:

• Flat panels produce less. A 100W panel lying flat on a caravan roof averages about 0.43kWh a day in Johannesburg, falling to 0.32kWh in June. In Cape Town it averages 0.41kWh but drops to about 0.18kWh in June. If you camp in the Cape in winter, size for that.
• Direction matters. East- or west-facing panels produce less than north-facing ones. The roof fit calculator adjusts for roof direction and pitch.

To check whether a small panel can keep up with a 12V appliance, compare the appliance's daily watt-hours from its specification sheet with the panel's output above. Leave a margin for cloudy days and battery losses.

Prices by wattage

These are single-panel, panel-only online prices. They exclude mounting, cabling, controllers or inverters, and installation. All are VAT-inclusive unless noted.

Retailer prices checked on 20 October 2026. Sustainable.co.za shows most prices as a sale against a higher "regular" price. Price-index figures checked on 26 September 2026. Price per watt is a SolarGuide calculation.

The lesson is that 100W to 160W panels cost two to three times more per watt than home panels. That's fine for a caravan, where a 100W panel is all that fits. It makes no sense for a house.

What does a 550W solar panel cost?

Of the four retailers we checked on 20 October 2026, only one listed a 550W-class panel: a Canadian Solar 555W at R2,450.13 from SunStore, with a three-panel minimum. That's about R4.41 per watt, more per watt than the 585W to 630W panels most retailers now stock. If a quote specifies a 550W panel, ask for the exact model and compare its price per watt with the current Solar Price Index. For a wider look at panel prices and what installation adds, see our solar panel prices guide.

For an existing installation, panel wattage is only one input. Read how to assess adding panels to your current inverter before assuming a higher-wattage replacement or extra string will fit.

How many panels for a given system?

Panel count is simple arithmetic once you know the system size in kilowatts:

Number of panels = system size in watts ÷ panel wattage, rounded up

SolarGuide calculation. Final counts depend on the inverter's string limits and the roof layout.

To work backwards from energy, divide the daily kWh you want from solar by your city's output per 1kW of panels. That's the 620W column above divided by 0.62, or about 4.8kWh a day in Johannesburg year-round. Covering 12kWh of daytime use there needs about 2.5kW of panels: five 555W panels, or four 620W panels if you can accept slightly less.

This is also why small panels don't work on homes. Fifty 100W panels would cover about 34 square metres of roof, while nine 555W panels cover about 23 square metres for the same 5kW. For the full sizing method, from your bill to a panel count, read how many solar panels you need. If roof area is the limit, our roof space guide shows how much each panel size needs with clearances.

Is a higher-wattage panel always better?

No. A 620W panel gives more power per panel and usually costs less per watt. But at 2.38m long and over 32kg it needs a long, clear run of roof. On a hipped roof broken up by valleys, vents and a chimney, more of the smaller 460W panels sometimes fit into the gaps and give a bigger total array. The bigger panels also run at higher current, which the inverter's inputs must be rated for.

Judge the total array in kilowatts on your usable roof, not the wattage of one panel. Alumo, SolarGuide's installation partner, uses 615W panels in its rent-to-own solar packages and 655W panels in its Essential subscription. It confirms the layout for your roof at the site assessment.

Want an itemised layout for your roof? Compare an itemised, compatible system for your home →

Frequently asked questions

How much power does a 100W solar panel produce a day?

About 0.4kWh to 0.5kWh a day on average in major South African cities when facing north at a 26° tilt, according to PVGIS. Lying flat on a caravan roof it produces less, and in a Cape Town winter it can fall below 0.2kWh a day.

How many watts of solar panels do I need for a house?

It depends on how much electricity you use in daylight and how much you want to store for the evening. Divide your target daily kWh by your city's output per 1kW of panels, about 4kWh to 5kWh a day across South Africa's main cities on a north-facing roof. A 3kW to 8kW array is roughly 5 to 15 modern panels; your bill and roof decide where you land.

Is a 550W or a 620W panel better?

Neither is better on its own. In current listings, 585W to 630W panels usually cost less per watt than 550W-class panels. The right choice is whichever gives the largest well-designed array on your usable roof, within the inverter's limits.

Can I connect a home solar panel to a 12V battery?

Not with a basic PWM controller. A 555W to 630W panel runs at about 40V and is designed for strings into a home inverter. For 12V systems, use panels designed for 12V charging, such as 100W to 160W modules, or a suitably rated MPPT controller.

Is SolarGuide the installer?

No. SolarGuide is an independent referral partner. Alumo supplies, installs, finances and warrants the systems. We help you compare options and get a free quote. All pricing is indicative and subject to a site assessment and credit approval.

Sources and review note

Checked on 20 October 2026. STC definitions, dimensions, weights, efficiencies and temperature coefficients come from Jinko's Tiger Neo 605W to 630W datasheet and the specification pages for the Cinco 100W, Cinco 160W, Cinco 200W and Canadian Solar HiKu6 460W on Sustainable.co.za and the Canadian Solar TOPHiKu6 555W on SunStore. Prices come from those pages, the SunStore Cinco 100W listing, the MacSell 150W listing and the Sustainable.co.za solar panel range, all checked on 20 October 2026, plus the SolarGuide Solar Price Index Q3 2026, checked on 26 September 2026. Daily output figures come from the European Commission Joint Research Centre's PVGIS 5.2, run on 20 October 2026. Alumo panel specifications come from alumo.co.za, checked on 20 October 2026. Price per watt, panel counts, areas and the PWM example are SolarGuide calculations from those figures. SolarGuide has not tested these panels, and none of these brands or retailers is a SolarGuide partner. If you spot a factual error, tell us and we'll correct it.