How much power (watts) should a solar system have in a motorhome?
The required power depends on your daily electricity consumption, the usage time of your devices, and the available sunlight. You can realistically calculate your needs in just a few steps.
If you would first like to understand how solar modules basically work and what types of designs exist, you will find a detailed explanation in our topic area on solar modules.
Step 1: Determine your daily electricity consumption (Wh)
List all the devices you plan to use while traveling:
- lighting
- refrigerator or cooler
- kettle or coffee machine
- Laptop, smartphone, e-bike
- fan or heater
- Other electrical consumers
Note for each device:
- Power in watts (W)
- daily usage time in hours (h)
Example:
| Device | watt | Hours | Energy consumption (Wh) |
|---|---|---|---|
| Smartphone | 10 W | 2 h | 20 Wh |
| fan | 50 W | 5 h | 250 Wh |
| Kettle | 1000 W | 1.5 h | 1500 Wh |
Total consumption: 1770 Wh per day
Step 2: Convert Wh to Ah (for 12V systems)
Motorhomes usually operate with a 12-volt system voltage.
Formula :
Ah = (Wh × 1.2) / system voltage
Example :
1770Wh × 1.2 / 12V = 177Ah
The factor 1.2 takes into account losses due to inverters and charging electronics.
→ 177 Ah is your daily electricity requirement.
Step 3: Calculate the required module power (Wp)
Now you need to determine how many watts your solar panel needs to deliver.
Formula:
Module power (Wp) × 0.75 × hours of sunshine / battery voltage
The factor 0.75 takes typical system losses into account.
Example:
A 340 Wp solar panel with 10 hours of sunshine:
340 × 0.75 × 10 / 12V ≈ 212Ah
→ Your requirement of 177 Ah would thus be covered.
What factors influence the calculation?
Actual performance depends on several factors:
- Weather (cloud cover reduces yield)
- Season (Winter vs. Summer)
- Region (Scandinavia vs. Southern Europe)
- Orientation and shading
- Roof area and roof load
- 12V or 230V system
- Quality of charge controller and battery
Always plan for a safety margin.
Mobile or fixed solar panels?
For motorhomes, there are usually three options:
- Flexible solar modules (lightweight, ideal for low roof loads)
- Framed roof modules (robust, permanently mounted)
- Foldable solar panels or solar bags (portable)
Which type of solar panel is best depends on your travel style, the available roof area, and your desired level of self-sufficiency. The differences between framed, flexible, and foldable solar panels are explained in detail in the relevant section .
How many watts are realistic?
For general guidance:
- Occasional campers with low energy consumption: 100–200 Wp
- Self-sufficient travel with refrigerator & technology: 300–400 Wp
- High energy demand or longer operating times: 400+ Wp
These values are guidelines – individual calculation remains crucial.
Frequently asked questions about solar systems for motorhomes
Is 200 watts enough in a motorhome?
For light use in summer, this may be sufficient. For higher consumption or winter travel, more power is advisable.
How many watts do I need for a refrigerator?
Compressor refrigerators require 30–60 Ah per day, depending on the model.
Can I retrofit solar panels?
Yes, provided the charge controller and battery system are compatible.
Next step
Once you have calculated your daily needs, you can now delve deeper:
- The basics, types and differences of PV modules are explained in detail in our section on solar modules.
- With the solar calculator you can determine your individual power requirements even more precisely.
- Next you will find suitable flexible, framed or foldable solar panels for your motorhome.
This is how you ensure that your system is technically suitable and will function reliably in the long term.
