How many solar panels do you need?

Energy consumption

How many solar panels you need depends mainly on your energy consumption. At home or at work, you look at your energy bill for this. It generally gives a good indication of the electricity used. Is it a mobile power supply? Then you calculate the energy needed by adding up the power of the individual devices.

The yield of your solar panels

To determine how many solar panels you need, we also look at the yield of your solar panels – and this in turn depends on a number of factors:

• Watt peak (Wp)
  The number of Watt peak indicates what your solar panels produce under optimal conditions. The higher the number, the better the panels are. However, in the Netherlands, conditions for solar panels are often not optimal. The yield is usually around 85%. By multiplying the number of Watt peak of a solar panel by 0.85, you calculate the average annual yield in kWh. On average, the number of Watt peak is around 350.
• Orientation
  The second point that affects the yield of solar panels is the orientation of the set-up. Solar panels facing south, for example, often generate more than solar panels facing north. An east-west arrangement is also popular. This allows solar panels to generate sustainable power evenly throughout the day.
• Shadow
  Although solar panels still generate energy, the yield is naturally less in the shade of, for instance, a tree or a chimney. Sometimes it is smarter not to install solar panels in those places. Especially if your panels are series-connected instead of parallel. The shadow then also affects the panels that are fully in the sun.
  Roof (or space) & set-up
  Last but not least, the roof or space the system will be installed on. Indeed, on a flat surface, the panels can be mounted at the ideal angle to increase efficiency. On a sloping roof, this becomes somewhat more difficult. And, of course, the surface area also plays a role. You can install more panels on a large surface.

Calculating how many solar panels you need

To calculate how many solar panels you will need, you can use a handy calculation: electricity consumption (kWh) / 0.85 / Watt peak (Wp) of the solar panel. Round up. For example, is your electricity consumption 3500 kWh and are you planning to buy 350 Wp solar panels? Then you will need 3500 / 0.85 / 350 = 11.76 (i.e. 12) solar panels to supply your electricity consumption.

Note: more is not always better!

Although it can be tempting, installing more solar panels than you need is not always a good idea. Admittedly, excess production is often fed back to the grid, for which you receive compensation through the net-metering scheme. But this scheme will eventually expire, which means that the compensation will also drop considerably. This also changes the payback period, so it may take longer to earn back your investment.

Tip: Are you likely to use more electrical appliances in the future, such as a heat pump? Or do you have a home battery? Then it may well pay off to have more solar panels installed!

Want to know more?

A specialist can calculate exactly how many solar panels you need. Do you need power on site and want to use a solar generator for this purpose? Then we would also be happy to help you find out, without any obligation on your part, what capacity you need and which model is best suited for the job. Feel free to contact us.