Low energy floodlights

[Dave Plowman]

If you were using car lamps you could always use the correct car cable for the low voltage side. However, a suitable 40 amp transformer wouldn't be cheap.

[Mark Evans]

With a lamp of the same characteristics it will always take more energy to use a 12V lamp and a transformer than a 230V lamp. Transformers are not 100% efficent devices.

The power rating of a lamp simply reflects its consumption of electrical power. A lamp's output of visible light is generally measured in lumens or lumens per watt.

There is a nice table at

most efficent is low pressure sodium, typically used for streetlights...

[Mark Evans]

1,000 joules of electrical energy per second.

Anyway different kinds of lamps have different efficencies in turning electrical energy into visible light. A 50W lamp of the most efficent kind will give off about as much light as a 1,000W lamp of the least efficent kind.

[stefek.zaba]

That table doesn't, though, give lumens-per-watt figures for 240V mains halogens of non-linear construction (GU10-type fittings), nor for 12V reflector halogens. It's been asserted repeatedly here that the thicker filaments of the 12V result in more light-per-electrical-watt than the weedy she-cannae-take-it filaments of 240V halogens; so that's a factor you have to balance against the inevitable, but possibly modest, losses in going down from 240V to 12V by either pure-induction transformer or the magick which is a switched-mode PSU (called an "electronic transformer" in the electrickal trade).

[The Natural Philosopher]

and halogen mains bulbs at 5 quid a pop that l;ast about a mointh on average are very expensive.

[N. Thornton]

Hi

Its rare that I'd disagree with Bigwallop, but I think I will on this one. AFAICS your power savings appear to have come from a) photocell operation, and b) lower total lighting wattage

It is also true that LV halogens are a bit more efficient than mains ones, but the setup cost is somewhat higher too.

I think CFLS are cheaper.

its between 60 and 70w. There are no 300% efficient power supplise.

As do 150w, 300w 500w and 1kW halogs. The larger size of the car headlamp reflectors acts to provide a narrower central light beam, and is not usually of any advantage for yard lighting.

yup, thats the issue, the lower power. You could of course use a 150w halogen instead of a 300. Its only when you need much lower powers than that that LV wins, simply because low power mains halogs are not much use.

In fact all controllers will work with mains halogens, but only some will work with LV systems.

and mains runs at zero cost.

Yes, that is a real plus in some locations. For home lighting tho, battery backup systems arent normally installed.

they're beaten by fluorsecent and CFL, or, if you dont mind odd colours, they're thrashed royally by sodium and mercury lights.

yes, there is a wide difference in efficiency of different types of bulbs.

I think you made the right choice, because of the want for battery backup, and the division of the lighting into separately controlled [low power] areas. But for home use the picture is quite different.

Regards, NT