Saving energy need not be a complicated affair, and in the current economic climate, the time is right to consider the simplest of energy-efficient retrofits. Dave Tilly does the sums

It’s been a tough winter for the commercial and the public sectors – as both wait to see what the effects of the Government’s spending cuts will be.

As a result, the installation of simple energy-efficient lighting schemes is likely to move up the business agenda. In the first two articles, we discussed MR16 and GU10 technology; now it is time to turn the spotlight on the simplest of energy-saving techniques – installing fluorescent tubes.

I will compare four technologies designed to replace T12 or T8 fluorescent tubes:

  • Eco tube. T8 tube that operates 10 per cent below nominal wattage.
  • Retro. T5 tube with in line control gear and spacer.
  • LED. T8 LED tube
  • Intel. T5 luminaires with occupancy and daylight sensor.

All the calculations will be based on 50 2 x 58W switchstart battens with point-for-point replacement. Energy consumption has been increased 20 per cent for switchstart.

Table 1

Before examining the merits of the different technologies, it is worth reviewing the savings generated over five years – 4,200 and 8,760 annual operating hours.

The only technology that does not require a labour content is the Eco tube. An estimated labour rate has been used for the remaining three technologies.

The tables below show the potential savings over a five-year period for 4200 and 8,760 operating hours.

Table 3

At 4,200 annual operating hours, the Retro product shows the best saving with the Intel technology just over £1,000 less. However, at 8,760 annual operating hours the Intel product trumps the others with the LED saving just £1,000 less over the five-year period.

Of course, there are a number of other important factors to consider:

  • The Intel and Eco Tube options have a manufacturers warranty. In contrast, the Retro and LED technologies demand that the existing luminaires are rewired, negating any manufacturer’s warranty.
  • The light distribution of the Retro and LED technologies differs from that which was originally specified. This will affect the application.
  • The introduction of new technologies, Retro and LED, to old luminaires can cause premature failures. This will have an impact on maintenance and replacement costs.
  • The introduction of Intel technology removes any possibility of controlling the lighting installation.

There will always be a lively discussion about switching policy – why would luminaires be left on when a space is not in use? But people often simply forget to turn lights off, or the installation is single circuit and something on the circuit must have power.

It is worth mentioning that even with point-for-point replacement, a new luminaire with a high light output ratio (LOR) may make it possible to run the original installation at a reduced wattage – perhaps lower that that of the retrofit systems – particularly if the original installation is over-illuminated, common in older installations.


As with most lighting projects, budget is a key ingredient. The Intel product may be viewed as the best option overall, but if the budget is restricted you may have to choose different options.

I always recommend that a lighting strategy is a feature of the operational plan for a business. This will ensure that the most appropriate technology is implemented without busting the budget. It may make more sense to refurbish smaller areas than planned and return to the remaining space when finance is available and some energy efficiencies have been accrued.

The benefits of a lighting strategy are:

  • Investment in lighting will follow the specification, regardless of the amount available to spend.
  • Procurement of light sources and luminaires will be standardised, improving future maintenance regimes.
  • The optimum balance will be struck between energy efficiency and the needs of the application.
  • New technology will be incorporated into future lighting projects.
  • The client brand and image will be protected.

There will always be an argument to install products like the Retro and LED on the basis that light levels and distribution are not really important. This may have some merit, but at what point does the lighting industry say, ‘efficiency is more important than the lighting scheme’?


The verdict is simple. The introduction of an Intel product, with the benefits of lighting control, new technology and manufacturer’s warranty will always be preferable to rewiring old luminaires and introducing compromise to a lighting scheme.

Showroom showcase

Times may be tough, but a new lighting scheme rather than a simple retrofit should pay dividends beyond simply cutting your electricity bills. Dave Tilley explains

Retrofits: do they add up?

Lux magazine introduces the Lighting Economist, Dave Tilley. His job is to work out the maths of lighting and energy – so you don’t have to. This month Dave solves a common problem: what’s the most cost-effective retrofit for low voltage halogen?