Solar panel sizing – get the most out of your system

A solar system can be sized in different ways depending on the goal, to maximize financial return or to generate as much electricity as possible. If you’re aiming for financial benefit, avoid oversizing the system, since using the electricity at home is usually more profitable than selling excess power to the grid.

Solar panel dimensions: approx. 1.72 m x 1.13 m

One solar panel is roughly 1.72 meters high and 1.13 meters wide. Panel sizes may vary by brand and capacity, so check the exact measurements for the model you choose.

Multiple panels are installed on the roof, and our experts will assess your site before installation.

The number of panels depends on several factors:

• How much electricity output do you want?
• What type of panel is selected?
• How much suitable roof space is available?
• In which direction can the panels be installed?

Solar panel capacity is expressed in watts peak (Wp) or kilowatts peak (kWp)

Typical residential solar panels have a peak power rating between 400–450 Wp. The actual performance depends heavily on the panel type, its technical features influence real-world output, even when the peak power rating is the same.

A typical residential system consists of around 10 to 20 panels. The system’s total peak capacity is measured in kilowatts peak (kWp), where 1 kWp = 1,000 Wp. So ten 400 Wp panels add up to 4,000 Wp, or 4 kWp.

Actual energy output is measured in kilowatt-hours (kWh)

Keep in mind that peak power reflects nominal performance under standard conditions. In real conditions, that level is rarely reached.

A 400 W panel typically generates around 350–380 kWh per year. So a 10-panel system would produce approximately 3,500–3,800 kWh annually.

Up to 30 years of performance warranty

Solar panels are a long-term investment. They can last for decades, which is why at Hehku we offer long product warranties, typically 25 to 30 years, depending on the model.

A performance warranty means the panel will still produce 85–90% of its original output after the warranty period (depending on the model). In other words, solar panels will keep producing efficiently for decades to come.

Other system components also come with strong warranties:

• Inverter (converts electricity): 10 years
• Mounting system: up to 30 years
• Installation: 5 years

Target: cover about 30% of your household’s electricity use

When sizing a solar system, the starting point is your total electricity consumption. In most cases, the best result comes from covering around one-third of your usage with solar power.

Why so? Solar panels produce the most electricity in summer and some in spring and autumn. In winter, production is minimal.

Meanwhile, electricity consumption often peaks during the heating season in winter. If your system is too large, you may produce more electricity in summer than you can use.

Using solar electricity at home is the most cost-effective option

Electricity produced by a home solar system is called small-scale or microgeneration. Sometimes, production exceeds what your household uses at that moment.

You can sell surplus electricity back to the grid, but using it at home is usually more profitable. That’s why it’s not wise to oversize your system just to maximize what you sell.

The smartest approach is to size your system so you can use as much of the electricity as possible yourself, and minimize the share sold to the grid. That’s how you get the best return on your investment.