In today’s world, data is everywhere. Improved data logging capabilities alongside widespread options to store, access and analyse data help diagnose systems in many industries.
Why log solar thermal data?
Data logging solar thermal systems can be a great way to:
- evaluate if a solar system is running efficiently
- determine if and when the solar system is overheating
- maximise the overall system efficiency. This enables you or an engineer to optimise the boiler controls for after heating.
How can I log solar thermal data?

Resol are the market leaders in solar thermal controllers. The DL2 offered by Resol logs solar thermal data. This add-on unit can be connected to any of Resol’s controllers to log key system data such as
- panel temperatures
- cylinder temperatures
- pump speeds
- faults
Analysing this data can help in increasing your solar system’s efficiency as well as diagnosing any faults or anomalies.
Data logging with Resol’s vBus
In general, Resol are using a feature on nearly all of their controllers called vBus. This is a communications protocol that can be used to connect to external devices that allows monitoring and analysis of the behaviour of your solar system. To make the data provided by vBus readable, there are a number of options at various levels and costs.
For all monitoring options, it is best to have a network an Ethernet connection available ? in fact, for live monitoring this is essential, although there is a Wifi option with the KM2 module.
Vbus.net
Vbus.net is Resols?s offering for remote monitoring and logging of data. The allows to connect to the Internet enabled devices listed below and show live data as well as letting you export historical data in standard formats (such as CSV) for further analysis or import into other tools. Resol?s vbus.net portal can be found here http://vbus.net. Generally, when purchasing a product with vbus.net access, you get access to the premium version for 30 days which will be moved to the basic version if you are not interested in paying the subscription. We find that basic (free) offering is sufficient for most users.
Data logging
For controllers that are not connected/cannot be connected to a network and/or the Internet, there are devices available that allow the logging of data on an SD data storage card. This data can be extracted and analysed in software such as Excel and others.
Pros:
- full access to all data a point of convenience
- absolute control and privacy control
- no further costs
Cons:
- no live data/monitoring
- manual process
Current controllers with built in data logging functionality

As an alternative to the DL2 data logger add-on, we can install a modern. Resol Controller that has integrated data logging facilities such as Resol SL, Resol SLL, Resol SLT or Resol BS Plus.
Please also check our controllers page if you are looking for other controller models.
Products
There are a number of Resol controllers available that include an SD card for data logging. Higher specification controllers allow for complex systems and set-ups, but the SL range is the entry level controller that includes and SD card slot. Alternatively, a DL2 data logger can be connected to a more basic Resol controller to log data. This Resol DL2 solution also includes access to vbus.net, see more below.
Data (live) monitoring
To monitor live data and get a current view of your solar system, you need to have a wired or wifi network connection available. There are various options to connect your system to Resol?s vbus.net:
Communications module KM2
This is a simple electronics module that connects your vBus enabled controller to the Internet via Ethernet or Wifi. With this module you get access to Resol?s vbus.net portal.
Pros:
- entry level connectivity to vbus.net
- Wifi enabled
- No manual data handling
- Can work with any vBus enabled controller
Cons:
- No access to data other than vbus.net
- No data logging away from vbus.net
DL2 data logger
A more advanced option for data logging and monitoring. The DL2 has a built-in web interface to allow you to access data from your solar system. It includes a data logging for historical data and also connects to vbus.net for remote monitoring.
Pros:
- Local and remote monitoring
- Data logging in the unit and via SD card
- No requirement for Internet connectivity if not desired, whilst allowing local network connectivity
- Can work with any vBus enabled controller
Cons:
- No Wifi connectivity, requires Ethernet connection
Analysis of the solar thermal data
Once we have the data of your solar thermal system, we prepare the data ready to visualise it with a data package. We then host the data on one of our own servers and give you password protected access. Below you can see some of graphs that we can produce. Please The data package allows you to zoom in on individual data points and points in time. This is particularly helpful to get a deeper understanding of your system. As a result we can offer advise on changing settings of your solar controller or your boiler settings.




