Here are the most frequently asked questions we receive about Voltage Optimisation. If your question isn’t here, fill in an ‘Ask a VPO® expert’ form and we’ll get back to you.

Don't just take our word for it...

“The powerPerfector at 3 Whitehall Place is a critical part of our energy reduction strategy, and has helped us to maximise our efficiency and reduce our carbon emissions.”

Jenny McInnes, Building DECC Team
DECC logo

Ask a VPO® Expert...

Our expert team are on hand to answer all your Voltage Power Optimisation needs, simply fill out the form below and we’ll be in touch.

Reason for enquiry
  • General
  • Technical
  • Purchasing
  • Student

Thank you for
your question.

A member of the
powerPerfector team will get in contact with you shortly, if your question is urgent please call:
0207 164 2271.
If you would like to ask another question please

Click here


Link for this page:

1) Why don’t I just tap down my transformers?

The savings achieved from a transformer tap will be a fraction of those achieved through a powerPerfector. In addition, there will be no benefit to power quality or any protection of your electrical infrastructure. The savings and benefits of a powerPerfector installation will quickly outweigh a transformer tap. In practice several major clients have discarded the transformer tap as a serious means to save energy and adopted powerPerfector technology.

VPO rule

2) Is powerPerfector a fixed or a variable (intelligent) unit?

It is both. The standard powerPerfector unit offers a fixed optimisation. The powerPerfector Plus works dynamically to optimise varying levels of supply voltage to a fixed output.

VPO rule

3) What are your average savings for an office?

We tend to see the greatest savings on facilities with large lighting and office equipment loads, including motors, refrigeration and air conditioning. Longer operating hours (high ‘load factor’) will maximise the savings made.

We would expect office sites with conventional equipment to see energy savings of between 6-12%. Please see our case study section for more information.

VPO rule

4) What is the lead time for units?

As each unit is hand built to match your individual site requirements it will take around six weeks to build and deliver the unit. powerPerfector Plus units may take up to eight weeks from the point of order.

VPO rule

5) I want a bespoke unit suitable for my site, isn’t powerPerfector an ‘off the shelf’ product?

powerPerfector is not an ‘off the shelf’ product. The unit size and optimisation settings are matched to your site’s requirements. powerPerfector Plus units are hand built to order in the UK.

VPO rule

6) How do you get savings if the current goes up when you drop the voltage?

Please see our document on VPO® and Ohms law, which answers this fundamental question.

VPO rule

7) Can I have a meter on the unit to show the savings?

We are committed to driving better accountability for savings measurement and validation in the UK, and would urge our clients to think carefully about how their other energy saving projects are going to be evaluated before they go ahead. If necessary, challenge your supplier to give you a thorough, objective analysis, and to prove that their conclusions are statistically significant: don’t settle for a single chart, a single figure or a magic meter to tell you what you have saved. All powerPerfector projects are externally evaluated using the IPMVP standard to determine the level of savings each has achieved. Please see more here

VPO rule

8) Why shouldn’t I just buy a low loss transformer when my transformer needs replacing?

In the past two to three years, a number of HV transformer manufacturers have started marketing “low loss” transformers, which also offer further tap settings (typically a ‐7.5% tap setting is made available in addition to the usual ‐5% to +5% settings), in theory bringing the voltage of a site closer to the optimum level. Although the extra tap setting increases the ability of an incoming transformer to bring the voltage to the optimum level, it is still much more limited than a standard powerPerfector unit which can optimise anywhere from 4%‐12% (the powerPerfector Plus unit offers dynamic selection of optimisation settings to react to fluctuating incoming voltage). Furthermore, bringing voltage to the optimum level via a low loss transformer does not necessarily offer any harmonic filtration or 3‐phase voltage balancing.

VPO rule

9) Will powerPerfector achieve savings where electronic ballast fluorescent lighting and variable speed motor drives are in use?

The energy use of most types of lighting will be reduced by supplying it at the correct voltage, including incandescent lighting and fluorescent systems with a reactive ballast.

For lighting systems with an electronic ballast there is less direct effect on energy use, but these systems are responsible for generating higher levels of harmonic distortion than a reactive ballast. As the powerPerfector helps to filter harmonic distortion, the efficiency of a site with electronic fluorescent lighting can be improved.

Similarly, there is a substantial opportunity to make savings where motor equipment is “direct online” and running at part load. However, when a variable speed drive is in use, the motor’s power supply is managed by the drive, so there is a reduced direct effect from the powerPerfector. Savings are made by filtering the harmful harmonic content these drives sometimes generate.

The powerPerfector's ability to filter harmonics and protect against common transients maximises the lifespan of sensitive electronic equipment including those mentioned above.

A full load assessment will be undertaken by a powerPerfector engineer prior to installation, to appraise the likely savings, based on the specific mixture of electrical loads at your site.

VPO rule

10) Is powerPerfector Power Factor Correction? How does it differ?

Power Factor Correction (PFC) is a method of improving the Power Factor by adding capacitive components to an incoming power supply. Having good power factor is important for the efficient operation of electrical equipment, and to prevent penalty charges being imposed by your electricity supplier. But installing PFC alone will not generate significant energy and carbon savings.

Installing a powerPerfector will result in energy savings of between 6-15% and the power quality improvements that are documented elsewhere. But, it will also cause an improvement in power factor.

powerPerfector does not contain any capacitive components, but by reducing the running currents to equipment the reactive impedance of that equipment is also reduced, lowering levels of reactive power on the site overall and lifting the power factor by between 3-10%.

VPO rule

11) We are having solar PV fitted – is it compatible with powerPerfector?

There is no conflict between having a powerPerfector and photovoltaics installed and in fact, the powerPerfector will be beneficial to buildings with PV systems. It may be that the settings on your PV will need to be adjusted to maximise the site's efficiency and allow the maximum benefit to be derived from the powerPerfector – for example preventing the PV from feeding in power at too high a voltage. This is something we will identify during the site survey and advise on prior to installation.

VPO rule

12) How do you help prepare shut down and will my systems reinstate following a drop in voltage.

Whilst powerPerfector may undertake up to 50+ installations and shutdowns each week we certainly do not get complacent about shutting buildings down. We recognise that every single shutdown should be managed and controlled to ensure the best possible results when re-energising at an optimised voltage. As such, we have a set of standard project controls that are tailored to meet the needs of our clients, their stakeholders and the building infrastructure.

VPO rule

13) I have old motors that are rated at 415V, will these still work?

For sites with a large proportion of heavy motor loads our engineers will analyse the loads on site to determine the likely cost and carbon savings achievable from powerPerfector. The nameplate rating of motors is part of this assessment, but in general their loading point is a much more important consideration than the nameplate voltage – lightly loaded motors can be made to run more efficiently by bringing the voltage to a more appropriate level for their loading point.

VPO rule

14) Our electrical engineers are recommending a bypass, does this come as standard on a powerPerfector?

There are a number of reasons why a small number of clients have enquired about having a bypass arrangement in order to quickly take their powerPerfector out of operation:

1. They wish to prove the savings attributable to the powerPerfector by switching it in and out of circuit and observing the effect on energy consumption.

• Please see our page on evaluating savings on the best way to analyse savings on site.

2. They wish to have the capacity at short notice to bypass what may be perceived as a potential failure point that has been introduced into the supply line to their building.

• Historic performance is the best indicator of risk: In over 4,500 units in the UK and tens of thousands installed worldwide over the last 19 years not one unit has failed and no insurance claim has ever been made from the failure of powerPerfector technology.

The powerPerfector is connected in series and has no moving parts. The powerPerfector Plus is also wired in series except for a control module based on solid state thyristor technology that controls voltage output, which is connected in parallel. This unit also contains no moving parts, and in the unlikely event of a failure in the electronics, the supply to the building will be maintained but without the voltage control on the existing supply. As a result, our clients can be absolutely confident in the reliability of the powerPerfector as a permanent part of the electrical infrastructure.

It is important to consider, that specifying a bypass does not mean that a standard voltage optimisation unit can be removed from circuit seamlessly. For a fixed ratio unit the power needs to be isolated before the bypass can be engaged, meaning that there is a short power outage associated with using the bypass.

A bypass installed with a powerPerfector Plus unit can be used without interrupting power.

VPO rule

15) What happens if we move premises or extend our site?

The size of the powerPerfector we install at your site depends on your highest maximum demand (in kVA) over the past 12 months. We would normally select a unit rated around 20% higher than your maximum demand. If you are planning to expand and anticipate that your electrical demand will increase we will allow more headroom by installing a larger unit. We have moved units between buildings in the past, but this is only possible in the rare occasions that the two sites have matching energy use and loads.

VPO rule

16) We have CHP at site – does it matter if the CHP goes ‘before’ or ‘after’ the powerPerfector?

In principle the powerPerfector can be installed either upstream or downstream of the point at which CHP feeds the site’s distribution system. As part of the site survey, our engineers will determine the best configuration for your site.

VPO rule

17) What is the guarantee offered on the units?

The unit itself has a warranty of 15 years, with an expected lifetime of 50 years.

powerPerfector also has a performance guarantee. If the evaluation shows that the unit has failed to achieve the estimated savings, we will reimburse you to ensure that you meet your guaranteed return on investment figure, so you will never be out of pocket.

VPO rule

18) Do you use three phase loggers to see what the voltage is? If not, why not?

Single phase voltage logging allows us to record voltage at a point distant from the electrical incomer, providing us with an essential measure of the volt drop across the site.

In our experience, this method captures the worst case voltage, allowing us to set the powerPerfector unit appropriately and to provide guaranteed energy savings without compromising the voltage levels on site. The phase balancing is checked later as part of the site survey process, so if a severe imbalance is detected the site can be re-logged to capture other phases.

Three phase logging can be used to support this process, for example on sites with a high proportion of three phase equipment. Generally however, single phase logging is a better solution, avoiding the need for a power shutdown to fit the logger.

VPO rule

19) What are the benefits of improved power quality?

Please visit the benefits pages of this website.

VPO rule

20) What are the differences between powerPerfector and autotransformers?

The two devices have fundamental differences. A ‘variac’ autotransformer is a mechanical device designed to control voltage by adjusting the tap setting of a transformer coil in response to changes in incoming voltage. Heating due to inefficiencies, and abrasion of moving parts means that these devices need regular maintenance and have short lifetimes.

A powerPerfector meanwhile, has no moving parts or electronic controllers, giving it a maintenance-free lifespan of 50+ years. Its functions (optimisation of voltage, transient protection, harmonic suppression and phase balancing) occur through the interaction of magnetic fields in its unique winding configuration. Further, advanced manufacturing techniques allow it to operate with a peak efficiency of 99.94%. This again sets it apart from an autotransformer, where efficiency may change substantially according to the load passing through the device.

The powerPerfector is designed to be an energy-saving device, optimised to address the problems of over-voltage and the electrical conditions of today’s grid. Autotransformers were developed for different applications and have been adapted to allow their suppliers to capitalise on the growing market for energy saving equipment. Only the powerPerfector has been designed from scratch to sit at the source of your building's power supply without introducing a risk of overheating or failure.

*The greengauge represents the aggregate savings of powerPerfector installations in the UK, Ireland, Cyprus and Denmark. Savings correct at the time of installation using either IPMVP savings analysis or reasonable estimates, where savings analysis was not possible. Actual savings may change over time for example due to energy pricing, occupancy, equipment, rates, building re-purposing and further energy efficiency measures.

All content copyright of powerPerfector Ltd 2015. All rights reserved.