Voltage optimisers

What are they...

Domestic voltage optimisers are often perceived as complex devices due to their sophisticated-sounding name. However, they are simpler than they appear. Contrary to what the name suggests, these devices do not ‘optimise’ voltage in the sense of stabilisation; rather, they reduce the incoming voltage by a fixed percentage, typically between 7-15%. Utilising a triodial buck-boost transformer, they are set up to decrease voltage but can also operate in reverse. Despite their simplicity, they are frequently marketed as a universal solution when, in fact, their application should be very selective.

Energy saving...

Voltage and Energy Consumption: In the UK, the average voltage supply is 242V. Contrary to popular belief, lowering this to the 220V commonly used in Europe does not yield significant energy savings. The reason is simple: energy suppliers bill for power consumption, which is measured in watts - a product of voltage and current. Reducing voltage often means appliances take longer to perform the same task, leading to no real gain.

Heating...

Heating Efficiency: When it comes to heating - be it water in kettles, cylinders, or dishwashers—the required energy remains constant. The misconception is that lower voltage equates to lower consumption. However, the truth is it merely extends the duration of the heating process. For instance, a heater with a 2kW output at 240V would see its output drop to approximately 1.7kW at 220V, a reduction of 16%, not just 10%. This necessitates a larger, potentially costlier heater to offset the decreased service.

Lighting...

Modern lighting technology has advanced to the point where it incorporates electronic components, typically including a microchip that precisely regulates the current. This regulation ensures a consistent amount of light is produced, regardless of voltage fluctuations. Such devices are referred to as voltage-independent; hence, reducing the voltage supply does not translate into energy savings with these systems.

On the other hand, traditional lighting systems, which may be less energy-efficient, could potentially use less power at a lower voltage. However, since these systems are designed to operate optimally at standard voltage levels, a reduction in voltage can lead to a noticeable decline in light quality.

The research...

The Carbon Trust

In 2011, the Carbon Trust published a document titled ‘Voltage Management’, which analyzed the potential energy savings from voltage optimization (VO) in commercial situations. The document suggested that reducing voltage could lead to lower power consumption, particularly for filament lamps and older fluorescent lighting. However, it’s important to note that the claim of a 13% reduction in energy consumption should be substantiated with current data, as lighting technology has evolved significantly since then and that within the report bizarrely the lack of light output was glossed over.

EA Technology

EA Technology, a leader in VO technology, conducted studies in 2012 that reportedly found energy savings, quantifying them at 8.5%. Yet, the methodology and results of these studies warrant scrutiny. For instance, the use of a tumble dryer timed rather than task-based led to an 18% reported saving, despite the clothes not being fully dry. Similarly, the use of a potato in microwave testing, instead of a consistent substance like water, raises questions about the reliability of the findings.

The selection of lighting loads in the study was also questionable, with a disproportionate comparison of 500W of outdated lighting against only 4W of voltage-independent LED lighting. Without measuring the actual lighting output, the results lack context and relevance.

The central heating pump’s performance was not evaluated under a constant flow, which is crucial since the power output of a motor is directly related to the voltage applied, as per the formula: P = V^2 / R. A 10% voltage reduction gives a power decrease of over 16%, affecting the flow rate. It’s also worth noting that most pumps offer multiple speed settings to accommodate different flow rates that would offer better efficiency at the sacrifice of fluid flow.

The assessment of refrigeration appliances was similarly flawed, as the energy consumption figures did not account for the operational cycles of the fridges and freezers, rendering the data less meaningful.

The Building Research Establishment (BRE)

The Building Research Establishment (BRE), responsible for the Standard Assessment Procedure (SAP) for Building Regulations and Energy Performance Certificates (EPCs), evaluated the potential energy savings of VOs within the UK context. Their document recognized an earlier version of EA Technology’s report but discounted some measurements due to the reduced level of service and come to a similar conclusion to mine.

Based on 2010 data, the BRE anticipated an energy saving of 2.2%. For an annual usage of 800kWh, this translates to a saving of 17.6kWh and, at a cost of 30p/kWh, a annual saving of £5.28. They also forecasted a decrease to 0.8% in 2015 and a further reduction to -0.2% in 2020, attributing this trend to the increasing adoption of newer, voltage-independent technologies.

Do they extend product life...

Products designed for the UK market are engineered to operate within a voltage range of 216V to 253V. Consequently, a voltage within this spectrum should not affect the warranty of the product. However, it is important to note that all products are designed with a specific life expectancy in mind. While it is theorized that operating at a lower voltage within the specified range may reduce stress on components and potentially extend their lifespan, current research on this subject remains inconclusive. A wiser investment might be surge protection.

Cost...

Whilst dodgy sales companies sell these for £1,000 - £5,000 they can easily be provided for £500. Even at this price and given the 5-year warranty the devices are not likely to make any notable savings and the money would be much better invested in more efficient lighting, better heating controls or more energy-efficient appliances.

Use with Solar...

Voltage optimisers are sold by unscrupulous companies for use with solar systems, stating warranty issues for inverters and loss of export etc. However, the RECC guidance G98 directly prohibits them.

Why...

It allows generation in excess of the statutory voltage limits given by the electricity quality safety and continuity regulations and therefore doesn't comply with G98 or G99.

In compliance with EN 50438, the interface setting for over-voltage of inverters is typically set to 262.2V (230V +14%). If the voltage output reaches that, the generation shuts down and voltage would need to reduce before returning to generating. The inverter needs to output a voltage slightly above the voltage level of the grid in order to export, usually 2% so around 5V.

But can they improve export...

A voltage of near 250V would be rare and a correctly designed and installed system shouldn't experience any issues as it would still be below the overvoltage setting.

Are they plug in and play and simple to install?

The installation of the devices is simple however some other points should be considered. These units are installed before the consumer unit. This point is usually before the isolation point and the network operator's fuse often needs to be removed. As these are sealed, and technically the energy company should be contacted to remove them. The installation/modification can impact the safety of every other circuit so these should be tested and the design would need to be verified.

The cables worked on carry all of the current feeding the property and have the highest fault current should an issue arise. Yet, as it's defined as a distribution circuit and not a final circuit, it's shockingly not notifiable to building control and the installers are often not professionally registered.

Isolating the power to the property, cutting the main cables and installing a large intrusive unit that affects every circuit in the property doesn't sound as plug-in and play as they like to claim.

It is unlikely that a company selling such a device would provide such due diligence however and will just slap these in without a care.