3 Technical SAPC Challenges Faced by Smart Meter Manufacturers

June 25, 2021

The Standalone Auxiliary Proportional Controller (SAPC) will soon be a requirement for smart metering devices. What does this mean for meter manufacturers?

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Standalone Auxiliary Proportional Controllers (SAPC for short) will be a mandatory requirement for all smart metering technology in the UK.

Yet meter manufacturers still face many questions, including:  

  • When do I, as a manufacturer, need to be compliant with SAPC? 
  • What needs to be ready in order to implement SAPC?  
  • How much is SAPC going to cost me to implement? 
  • What are the benefits of SAPC to me, the manufacturer, and my customers?  

While SAPC is not due to be made compulsory until 2024/25, the answers to some of these questions remain elusive. But that doesn’t mean manufacturers cannot have a good idea of what they should expect when SAPC goes live. The three technical challenges of interpreting, implementing and testing offer an insight into what the future holds for meter manufacturers regarding SAPC.  



Interpreting the guidance that exists for SAPC is key to ensuring manufacturers remain compliant with relevant standards. These standards are set by the UK Government’s Department for Business, Energy and Industrial Strategy (BEIS) and the Data Communications Company (DCC). The standards cover the management of grid energy supply, the monitoring of electricity loads from the grid to the household or business, and the security of transferring electricity from the grid to the household/business.  

Correctly interpreting requirements is essential as SAPC demands the use of complex protocols like the Great British Companion Specification (GBCS) which are needed to integrate SAPCs effectively into existing smart metering equipment. Failing to interpret GBCS standards accurately can lead not only to major project overspend but also to significant delays in bringing products to market.  





Implementing SAPC poses a specific challenge relating to how it communicates with smart meters. The intention is for SAPCs to use Zigbee radio devices to transfer communicate bi-directionally to smart meters. The meter’s communications hub is critical to this.  

Meter manufacturers need to be able to ensure not only that this communications channel works, but also that it is reliable and secure. For instance, cryptographic measures should be used to protect the data transferred using Zigbee from outside interference.  




Multiple phases of testing will be needed to ensure SAPCs are capable of effectively managing energy loads. These tests should produce functionality evidence which can be assessed by the DCC and BEIS, ensuring standards compliance and compatibility with existing SMETS2 devices.  

A GBCS stack can assist manufacturers in offline testing SAPCs. Using C/C++ coding following conventions including MISRA and AUTOSTAR, manufacturers can determine the operability of SAPCs and ensure they function as expected.  

Beyond this, online testing is needed to ensure that functionality for the customer will work as it should. This requires the collation of relevant standards and rules which must be applied to devices before they enter the market.  


Preparing for SAPC 


In future, manufacturers will need to dedicate more of their development time to ensuring their devices are fully compatible with SAPC, avoiding the prospect of their meters quickly becoming outdated.  

Interpreting, implementing and testing SAPCs requires significant resources and, ultimately, these may carry a noteworthy price tag - making it vital that manufacturers are aware of their options when guaranteeing the accessibility and compliance of their devices.  

Partnering is one way to ensure manufacturers have the necessary expertise all the while keeping costs low. Find out how Critical Software can help you become SAPC-ready with our free assessment