CS-rated halogen fitting

More fittings increases the heat loss – although doubling the number of fittings doesn’t double the loss.

There was some reduction in heat loss when RS- or CS-rated fittings were replaced with CA fittings (see About our test for what the ratings mean). This happened whatever bulb was used.

See the “Extra room-heating required” column in our test results table – it shows how much extra heat was required to keep the room at 20°C, so you can also see how the heat loss varies with different fittings and bulbs.

Changing bulbs

CA kit fitted on the halogen light

Swapping a standard incandescent GLS bulb with an R80 reflector bulb in the same fitting also reduced heat loss. We suspect there are two reasons for this.

First, reflector bulbs are larger in diameter than the standard bulbs and this means they “fill up” the fitting better, reducing the air gap around the bulb. Second, these bulbs also reflect light and heat downwards – this would result in the fitting running cooler, which in turn would reduce convection currents of warm air through the fitting.

Swapping to a CFL bulb reduced the energy loss even further. But we have reservations about fitting CFLs into recessed fittings not designed for them. Good CFLs produce at least as much light as their equivalent incandescents, but when fitted to older recessed fittings they often “stick out” a bit.

This means the reflector doesn’t work properly, the light bounces around inside the fitting and the resulting light output is not as good as it should be.

In halogen fittings, the heat loss from the halogens decreased a little when the optional CA kits were used.

Fitting payback

We did calculations for a typical 5m x 4m living room with an insulated ceiling, uninsulated walls and a wooden floor. Our "What size heatpump" calculator says it would take 3kW to heat the room.

From our test results we estimate it would take 5.7kW to heat the room if it had six R-rated downlights in the ceiling.

Replacing those six R-rated downlights with CFL-specific CA models would reduce the heating required to 3.75kW. The fittings would pay for themselves in less than a year (if the room was heated with electric heaters) or in just over two years (if using a heat-pump).

These calculations include the cost of the new fittings ($26.55 each) and $300 for an electrician to fit them.