Making brighter cities

Using Your Connected Streetlight Central Management System to Meter Energy Consumption

Sarah-Jane Allen on 27 September 2019
Picture of Sarah-Jane Allen
BLOG-QA-Ron and Keith
  1. How can cities use their Central Management System (CMS) as a meter?

Some wireless streetlight control nodes have a power metering capability. So adopting an intelligent street lighting system that consists of wireless nodes to connect all streetlights, with dedicated network connectivity and a CMS, can create an accurate picture of actual energy consumption.  By placing a conventional mains supply meter on just one sample streetlight circuit, the consumption can be compared with the CMS-metered figure on the same circuit to calculate a correction factor of energy consumption. This correction factor can then be applied to the whole network, so cities can pay for actual energy consumption without the need for costly installations of mains supply meters on all circuits.

Haven’t seen our easy info-graphic on ‘Using your connected streetlight CMS as a meter?’ Find out more.

  1. Do you need a large network to see the benefits of using CMS as a meter?

No, you do not need a large network, using your CMS as a meter to achieve energy settlement can be applied to a small number of streetlights and still achieve reductions of up to 12% in measured energy consumption.

  1. How do you choose the sample of streetlights to be measured?

The sample of streetlights needs to be representative of the geographic area. The location of metering needs to be considered to ensure that the only load being metered is the street lighting load and each luminaire has a node connected to record the individual luminaire’s consumption.

  1. How often do you need to calculate the correction factor?

The sample of streetlights need to be measured on an ongoing basis and the correction factor is calculated monthly, comparing the metered circuit of streetlights with the sample of CMS metered streetlights on the same circuit. The results are then applied to correct the energy consumption of all nodes in that month.

  1. How does this approach differ from the Distributed Unmetered Load (DUML) approach?

DUML estimates electricity consumption by multiplying the installed streetlight capacity with the running hours of the streetlights. This approach does not recognise dynamic on-and-off or dimming of streetlights, it assumes that all lights run at 100% for the entire period that the lights are on. Furthermore, if one consumer is undercharged for their consumption other consumers will be paying to make up for this through the assumed losses. This also requires the council to maintain a streetlight database which can be time consuming and costly.

  1. How is this approach more cost-effective than using the traditional DUML approach as it seems to bear a lot of upfront cost?

The traditional method of energy settlement assumes a maximum load for each streetlight. These loads are typically charged on a per streetlight per day basis. For example, the electricity company might estimate the maximum load of a streetlight at 49W per pole, but the actual average measured load is 27W. Applying this to operating hours of 4,300 per annum and a sample of 1,000 streetlights, the difference in energy consumption is 45%. The table below demonstrates this principle.


  1. How does Telensa’s connected street lighting calculate energy consumption?

The Telecell (node) has a revenue grade metering chip and this is used to record the consumption of each luminaire connected to a Telecell. This data is recorded in two formats for energy settlement - meter reading and energy consumption. For the purposes of this process the meter reading is used.

  1. How does Telensa’s CMS differ from council-kept streetlight databases?

The inventory held within the Telensa PLANet system is a slave copy of the street lighting inventory held by the council. Telensa adds additional fields to those normally held by the council including GPS location, meter readings, fault reporting, monitored data and the ability to monitor and control the lighting infrastructure to suit each location.

  1. Can the CMS integrate with a council streetlight database?

The Council street lighting database will normally be used as the master database and PLANet (the CMS) as a slave to this database. Information on assets, luminaires, locations etc. are normally exported from the master database into PLANet. The data captured within PLANet which is not normally held in the council database can be exported from PLANet and imported into the council database. Information typically exported is fault reports and GPS location information.

  1. How does a city use the calculated correction factor to reduce their payment for energy consumption?

The meter reading for all of the Telecells will be collected as a cumulative figure at the end of each month. The smaller sample set will also be collected at the end of each month and compared to the electricity meter reading which will be read remotely at the end of each month. There is a small manual intervention required to pass the cumulative and subset readings to the Retailer for them to calculate the usage compared to the correction factor. If the Retailer is given access to the PLANet system they can independently verify these readings for themselves.

Do you want to find out more? Get in touch to speak with our APAC Manager, Keith Henry on


Topics: Smart cities, smartstreetlights