In the first two parts of our series "Self-sufficient for the season," we covered the basics of self-sufficient power generation in vehicles and the selection of the appropriate supply battery . In the third part of the series, we will now address the question of how this energy can be generated efficiently and reliably. The focus is on the selection of solar modules and the associated charging technology, as they form a fundamental building block for an independent power supply on the go.
We will explain the key differences between monocrystalline and polycrystalline solar modules, provide guidance on the required solar power, and determine which charge controller – MPPT or PWM – is best for which application.
What types of solar modules are there? Monocrystalline vs. polycrystalline
There are various types of solar modules on the solar market, and the differences may not be immediately apparent to beginners. We'll explain – two technologies in particular dominate module construction: monocrystalline and polycrystalline Solar modules. Both technologies are based on silicon as a semiconductor material, but differ in their manufacturing process, efficiency, and application possibilities. A closer look at the differences helps you make the right decision for your specific application.
Monocrystalline solar modules – efficient and space-saving
Monocrystalline modules consist of a single, high-purity silicon crystal. Manufacturing is more complex, but the result is a very powerful module with high efficiency. These modules are usually black or dark grey and are characterized by a homogeneous cell structure out of.
✅ Advantages:
- High efficiency (up to 22%): Ideal for limited space
- Good performance in low light: Reliable even in the morning, evening or under cloudy skies
- Long service life: Particularly robust due to high-quality workmanship Modern, uniform design: Often preferred for aesthetic reasons
Areas of application:
- Vehicle roofs (campers, motorhomes, boats)
- Balcony power plants
- Applications with limited space and high power requirements
Monocrystalline solar modules like the WATTSTUNDE SOLA Frame Series are therefore the first choice when efficiency and longevity are paramount.
Polycrystalline solar modules – proven and cost-effective
Polycrystalline modules are made from multi-crystallized silicon. The structure of the cells is therefore grainy and usually shimmers bluish . The manufacturing process is simpler, which is reflected in a cheaper price reflects.
✅ Advantages:
- More cost-effective to purchase
- Solid performance under standard conditions
- Proven technology with many years of market maturity
In direct comparison to monocrystalline modules:
- Slightly lower efficiency (usually 15–18%)
- Larger area required for the same performance compared to monocrystalline modules
- More sensitive at higher temperatures
Areas of application:
- Stationary systems with sufficient space (e.g. garden sheds, garage roofs, permanently installed off-grid systems)
- Budget-oriented applications without space restrictions
The choice depends on the application
For mobile applications such as campers, boats or off-road vehicles we recommend monocrystalline modules as they are more power per area in limited space and operate more reliably in changing light conditions. So, if you want to start the season autonomously with your vehicle, then monocrystalline modules are the right choice! Polycrystalline modules are still an economically interesting solution if lots of space available and the budget plays a bigger role.
Framed vs. flexible solar modules – which design is best for your application?
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In addition to cell technology, Design of the solar module play a crucial role – especially in mobile applications such as in campers or on boats. A basic distinction is made between framed and flexible Solar modules, each of which offers different advantages.
Framed solar modules – robust & powerful
Framed modules consist of a sturdy glass or glass/glass construction, enclosed in an aluminum frame. This construction method offers maximum stability and durability.
✅ Advantages:
- Very robust – ideal for permanent installation on vehicle roofs or in fixed systems
- High power output thanks to optimal cell structure and better cooling
- Resistant to wind, weather and mechanical stress
- Long-term investment with a long service life
The WATTSTUNDE SOLA Frame series is an example of high-quality, framed modules that are particularly suitable for those looking for a durable, high-performance solution.
Flexible solar modules – lightweight & adaptable
Flexible modules are made of lightweight, flexible materials without glass covers or rigid frames. They can be installed on curved surfaces or in locations with special requirements.
✅ Advantages:
- Extremely light & flat – perfect for sensitive or weight-optimized roofs
- Easy installation – often possible without drilling (e.g. gluing)
- Unobtrusive design – integrates well into the vehicle’s appearance
- Partially accessible, ideal for boats
The WATTSTUNDE SOLA Flex Series is ideal for applications with limited load capacity or irregular surfaces, for example on campers, vans, boats or expedition vehicles.
Choose design according to intended use
Framed modules are the right choice when it comes to maximum performance, stability and longevity arrives. Flexible modules are suitable if Weight, mounting freedom and adaptability be in the foreground.
The right combination of technology and design is crucial to getting the most out of solar energy – tailored to your vehicle, your everyday life, and your energy needs.
How much solar power do I need?
This question is directly related to your individual electricity consumption. A brief overview of typical energy consumption will help you estimate. To find out how much Solar power (Wp) You need, you must first daily energy consumption in watt-hours (Wh). A simple calculation helps here - let's look at the formula and example consumer again Part 2 this blog series.
Formula for calculating consumption:
Power (W) x operating time (h) = consumption in watt-hours (Wh)
Step 1: Determine daily electricity consumption
Write down which devices you use and for how long per day:
| Device | Consumption (in watts) | Usage time/day | Consumption/day (in Wh) |
| LED light | 10 W | 5 hours | 50 Wh |
| Compressor refrigerator | 50 W | 12 hours | 600 Wh |
| laptop | 60 W | 3 hours | 180 Wh |
| Kettle | 1500 W | 5 minutes | 125 Wh |
👉 Total consumption per day: ~955 Wh
Step 2: Conversion into solar power
A solar module does not supply electricity around the clock, but only when exposed to sunlight – and even then, the output fluctuates depending on the time of day, weather, and orientation.
As a rule of thumb: 100 Wp solar module power generate in Central Europe on average about 300–500 Wh per day.
This depends, among other things, on:
- Season (summer vs. spring/autumn)
- Location
- Alignment & inclination of the module
- Shading
- Quality of the module and charge controller
Step 3: Calculate performance
As determined above, the daily consumption is approx. 955 Wh per day.
A 100 Wp module produces (realistically) about 350 Wh/day.
Formula for calculation:
Daily consumption ÷ yield per 100 Wp
955 Wh (daily consumption) ÷ 350 Wh (yield per 100 Wp) ≈ 2.73 → You need approx. 280 Wp .
Since weather and orientation are not always ideal, you should Buffer of 20 to 30% So plan generously!
In this case, 350 - 500 Wp the safe choice.
| Daily consumption | Recommended solar power (with buffer) |
| approx. 300 Wh | 120 - 150 Wp |
| approx. 500 Wh | 180 - 250 Wp |
| approx. 800 Wh | 300 - 400 Wp |
*This table reflects guidelines; please always check again to see if it is suitable for your own consumption.
The higher your consumption or the more weather-independent you want to be, the larger your solar system should be – especially for longer trips or in winter. Combined with a good MPPT charge controller, you'll get the most out of it!
Charge controller: MPPT or PWM – which is better?
A charge controller is that Link between solar module and battery . It ensures that the energy generated by the solar modules is fed into the grid in a controlled, safe and battery-friendly manner. two basic types: PWM and MPPT. But what differentiates them – and which one suits your system?
PWM charge controller (pulse width modulation)
A PWM controller is the simpler and cheaper option. It works on the principle that the voltage of the solar module is “regulated down” to the level of the battery voltage.
To put it simply:
If your solar module delivers a voltage of, for example, 20 V, but your battery requires 12 V, the excess is simply "cut off" and lost as heat.
✅ Advantages of PWM:
- Inexpensive to purchase
- Easy to use
- Sufficient for small systems with well-matched module and battery voltages
❌ Disadvantages:
- Energy loss, especially when solar radiation is not optimal
- Less suitable for larger or more powerful systems
- No optimal use of available solar power
- For very small, simple systems with short operating times, PWM may be sufficient
MPPT charge controller (Maximum Power Point Tracking)
A MPPT controller is the smarter and more efficient solution. It constantly analyzes the voltage and current of the solar module to find the so-called maximum power point – the point at which the module delivers the most energy.
Instead of wasting excess voltage, the MPPT controller converts it into additional charging current. This allows it Get up to 30% more energy out of your solar modules – especially in low light, low temperatures or partial shade.
✅ Advantages:
- Significantly higher efficiency – more usable energy
- Ideal for all weather conditions
- Enables the use of more powerful modules
- Perfect for larger systems or year-round travel
❌ Disadvantages:
- Higher price than PWM
- Some more space and technical understanding required
If you want to get the most out of your solar system – especially in tight spaces like in a camper or on a boat – you should opt for an MPPT controller.
What does this mean specifically for your setup?
| System size | Recommendation |
| Small system (e.g. 100 Wp, occasional use) | PWM sufficient |
| Medium-sized system (e.g. 200 - 400 Wp) | MPPT recommended |
| Large system or year-round use | MPPT highly recommended |
Important : When selecting your MPPT controller, pay attention to the correct voltage class (e.g. 75/15 or 100/20) – this number indicates which module voltage (V) and how much charging current (A) the controller can handle.
Conclusion: Use solar energy cleverly
The Combination of the right solar modules, a suitable power design and intelligent charging technology are the key to an efficient and self-sufficient power supply on the go. Whether in a van, boat, or self-sufficient weekend home – with the sun as your energy source, you're flexible and independent on the go.
Preview of Part 4: Inverters & Power Conversion
In the next part In our series we take a look at the Inverter – the central component that converts 12V DC to 230V household current How much power do you need and what is the Difference between a sine wave inverter vs. modified sine wave? Part 4 gives you the answers, so stay tuned and start the season self-sufficient with SOLARKONTOR!
Links:
Missed part 1?
Here go to the article: Basics of self-sufficient power supply
Part 2: missed it?
Here go to the article: Finding the right supply battery
