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Voltage Reduction and Regulation3450_8-img-200x265-13 - - becky

Are you baffled by the aggressive marketing of suppliers in this field and dubious about extravagant savings claims?

The cost-effectiveness of such equipment is extremely variable and depends not just on supply voltage but on site characteristics and the mix of electrical equipment you use.

Learn more about voltage management

Put us to the test NOW!  To discuss your requirements please call John Treble on 01761 419081 or email John@GreenConsultancy.com

The Green Consultancy can provide you with independent advice on whether or not you need to do anything in relation to your electricity supply – and, if so, what is the most cost-effective solution for you.

The voltage at which a particular item of plant and machinery is supplied can have a significant effect on its efficiency and operation. Historically, the supply voltage in the UK was 240 volts (phase to earth) but since European Union harmonisation regulations came into force this has been reduced to 230 volts.

In reality, there has been no change: the range of acceptable voltages has simply been widened to accommodate the lower “continental” voltage and the actual UK limits are now 230 volts minus 6% (216.2 volts) to plus 10% (253 volts). All equipment sold within the EU has to be capable of operating throughout this range of voltages.

Numerous site investigations have shown that the supplied voltage does, in fact, vary from less than 220 volts on some sites to over 250 on others, and in some cases the statutory limits are being breached.

However, the vast majority of sites suffer from excessive voltage. This is due to the traditional design of transformers that are built to provide 250 volts (433 volts phase to phase) in the no-load situation, and rely upon the site’s electrical load to bring this down to around 240 (415). As many transformer installations are over-specified, the result is that the distributed voltage is invariably in excess of 240.

The voltage at an individual site can also vary considerably depending on the demand profile and any variation in the supplied grid voltage at that location. Investigation is needed at those sites that are operating at the top end of the voltage range, but may also be beneficial for sites operating at lower voltages, particularly where security of supply may be an issue.

Learn more about Voltage Management

The Green Consultancy’s comprehensive service

We will be pleased to provide whatever level of investigation is appropriate for your estate. If you have a site with many buildings, supplied it high voltage, with one or more of your own transformers then you are likely to need a full survey and feasibility study.

  • Investigate the voltage profile of a site; voltage drop; the existing supply infrastructure; the nature of the site’s demand in terms of process and plant; and the opportunities for cost-effective remedial works.
  • Consider both the voltage profile and the site’s kW demand profile as the highest voltages usually occur with the lowest demand and this will reduce the potential savings.
  • Consider the actual nature of the electrical loads, as some - such as IT equipment - provide no reduction in consumption at all with a reduced voltage, while others may produce savings that are significantly greater than pro-rata.
  • Consider the cost-effectiveness of all options to reduce energy consumption.
  • Provide a comprehensive report detailing the recommendations; potential savings; costs; future infrastructure changes and the effect that these may have.

For an example of such an investigation please see: University of Portsmouth Case History

If you have a large number of relatively simple sites it will probably make more sense to adopt a phased approach as follows.

Phase 1 - desktop benchmarking exercise of all sites and report on potential cost-effective opportunities. The information we need for each site is:

  • site name and address
  • function of site
  • annual electricity consumption (half hourly data if available)
  • number of supplies
  • number of own transformers
  • types of electrical equipment and any information available on the split of consumption between types

Phase 2 - visit all sites not eliminated in phase 1 to:

  • measure incoming voltage on each supply and voltage drop across the circuit.
  • consider the electrical loads in detail in terms of potential energy savings
  • report on potential cost-effective opportunities

Phase 3 - visit all sites not eliminated in phase 2 to log voltages for at least a week and make recommendations. In the process it is highly likely that we would identify other energy reproduction opportunities which we would also report on.

If you have a single site supplied at low voltage then it can be investigated one step at a time, to keep the cost as low as possible, as for the above phased approach.


Put us to the test NOW!  To discuss your requirements please call John Treble on 01761 419081 or email John@GreenConsultancy.com

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Voltage Management for University of Portsmouth

“The Green Consultancy’s solution is elegant and maximises energy efficiency at the lowest cost. Salesmen were queuing up to sell us secondary transformers when we already had too many transformers and the result would have been less savings at greater expense.
I have always been impressed with The Green Consultancy’s sound scientific approach to identifying energy reduction opportunities.  I thoroughly recommend them and look forward to the project implementation and further studies by them.”

Ian McCormack, Energy and Environment Manager

See case history of our work for University of Portsmouth


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John Treble

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For over twenty five years we have been delivering superior outcomes for thousands of commercial, industrial and public-sector clients.

You need not take our word for it – hundreds of their comments are at the foot of these pages.

To discuss your requirements please call John Treble on 01761 419081 or email