Choosing the Right Panel Wattage

Walk into any solar supplier in Harare and you will see panels ranging from 330W to 680W. The natural instinct is to go for the highest number — bigger must be better, right? Not always. The right panel wattage depends on your roof, your inverter, your budget, and how many panels you can physically fit and transport.

This guide helps you work through those trade-offs so you choose panels that make practical and financial sense.

The Sweet Spot for Zimbabwe

Panel pricing does not scale linearly with wattage. There is a range where you get the best watts per dollar, and right now that range sits between 450W and 550W for the Zimbabwean market.

The 450-550W range is the sweet spot because these panels use current-generation cell technology (typically 144 half-cut monocrystalline cells), are produced in massive volumes, and are widely stocked by Zimbabwean suppliers. You get modern efficiency without the handling headaches of oversized panels.

72-Cell vs 60-Cell Panels

Solar panels come in two main form factors based on cell count:

60-cell panels (120 half-cut):

• Typically 330-400W
• Smaller physical size (about 1.7 m x 1.0 m)
• Lower voltage per panel (around 37-40V Voc)
• Easier to handle on tight roofs

72-cell panels (144 half-cut):

• Typically 450-580W
• Larger physical size (about 2.3 m x 1.1 m)
• Higher voltage per panel (around 45-50V Voc)
• Better watts per square metre of roof space

For most residential installations in Zimbabwe, 72-cell panels in the 450-550W range are the standard. They fit standard residential roof dimensions, and installers stock the mounting hardware for them.

Roof Space: Fewer Big Panels vs More Small Panels

This is a practical decision that many people overlook until installation day.

Scenario: You need 4,400W of panels. You could install:

• 8 x 550W panels — requires about 20 sq m of roof space
• 12 x 370W panels — requires about 24 sq m of roof space

Fewer panels means:

• Less mounting hardware (rails, clamps, end caps)
• Fewer cable connections (each connection is a potential failure point)
• Faster installation time
• Less visual clutter on the roof

More panels means:

• Each panel is lighter and easier to carry up a ladder
• You can fit panels around roof obstacles (vents, skylights, chimneys)
• If one panel is shaded, a smaller proportion of your total array is affected

Voltage Considerations: Check Your Inverter Limits

This is where people get caught out. Higher wattage panels generally produce higher voltage — and your inverter has a maximum input voltage that must not be exceeded.

Every panel has two voltage specs that matter:

• Vmp (Voltage at Maximum Power) — the operating voltage under load
• Voc (Open Circuit Voltage) — the voltage when nothing is connected (always higher than Vmp)

When panels are wired in series (which is how most residential strings are configured), the voltages add up. Three panels at 49V Voc each produce a string voltage of 147V open circuit.

Your inverter has two critical voltage limits:

The danger: On cold mornings, panel voltage increases (the opposite of what most people expect). A string that measures 140V on a hot afternoon might hit 160V at dawn in winter. If your inverter's max input is 145V, you have a problem.

Shipping and Handling Realities

In Zimbabwe, most solar equipment arrives by road from Beira, Durban, or via Harare distributors. Larger panels mean:

• Higher breakage risk in transit — a 2.3 m panel flexes more than a 1.7 m panel on a bumpy road
• Harder to carry up stairs and onto roofs — a 600W panel weighs 30-35 kg and is awkward for two people on a ladder
• More difficult on complex roof layouts — turning a 2.3 m panel around a hip or valley on a tricky roof is genuinely hard

If your roof requires climbing, narrow access, or working around obstacles, the practical advantages of a slightly smaller panel (450W vs 580W) can outweigh the marginal price-per-watt savings of the bigger one. Ask your installer what they prefer to work with on your specific roof.

Diminishing Returns Above 550W

Panels above 550W exist and work well — but for residential installations, the returns diminish:

• The price-per-watt advantage flattens or reverses
• Physical size and weight increase
• You need fewer panels, but the ones you have are harder to replace if damaged
• String sizing becomes less flexible (fewer panels per string means less room to adjust voltage)
• Local stock is thinner — if a 600W panel breaks, finding an exact replacement locally is harder than finding a 540W

Commercial rooftops with flat mounting and crane access love 600W+ panels. Residential rooftops on suburban homes generally do not need them.

Calculating Your Total Array Size

Once you know your inverter capacity, you can work backwards to find the right number of panels.

Step 1: Know your inverter's DC input capacity.

Most residential inverters accept 1.0 to 1.3 times their AC rating in DC input. A 5kW inverter typically handles 5,000-6,500W of panels.

Step 2: Choose a DC/AC ratio.

Step 3: Calculate panel count.

Total panel wattage = Inverter AC rating x DC/AC ratio

Number of panels = Total panel wattage / Individual panel wattage

Example: 5kW inverter with 1.2 DC/AC ratio using 550W panels:

• Total array: 5,000 x 1.2 = 6,000W
• Panels needed: 6,000 / 550 = 10.9 — so 11 panels

Step 4: Verify string sizing.

Check that 11 panels wired across your inverter's MPPT inputs stay within the voltage and current limits. This is where the Match Builder tool saves you from manual calculations.

Quick Decision Guide

Not sure which wattage to go for? Start here:

The best panel is the one that fits your roof, stays within your inverter's limits, is available locally with warranty support, and gives you competitive price-per-watt. Everything else is secondary.