halogen to LED conversion

Our new house was somewhat overlit when we moved in: if all the lights had been working and turned on at once, they would have drawn nearly 1.5kW. There were twelve lights that weren't working, because of dead transformers or blown bulbs, but such was the redundancy that replacing those didn't seem urgent. It did, however, give me an opportunity to switch a huge variety of halogen bulbs to LEDs or compact fluorescents.

The lighting was I think put in by the owner before the previous owners, who did a lot of work himself. And back then halogen downlights were popular...

• The entry hallway had five 40 watt GU10 halogens. Covering maybe two square metres, this made the hallway, even with only three of the lights working, the best lit area of the entire house.
• The sitting and dining room were lit with twenty one exposed 20 watt G4 halogens, nine of them in the sitting room and twelve in the dining room. This provided decent light, but was unpleasantly bright.
• The kitchen had four 60 watt R63 spotlight bulbs plus three 18 watt benchtop fluorescent bars and an 11 watt rangehood light; the breakfast area had four dimmable 35 watt GU10 halogen spotlights.
• The bathroom had five 20 watt MR16 halogens (I use "MR16" to refer to MR16 reflectors with GU5.3 connectors, as seems to be common usage).
• The upper hallway, with two 5 watt compact fluorescents, and the nursery and main bedroom, with one 11 watt compact fluorescent each, were comparatively sanely lit.
• The study had four 50 watt MR16 halogens and the ensuite one 20 watt MR16 halogen.
• The patio had ten 60 (?) watt incadescent multi-coloured party lights, of which only three were still working. The shed had several bar fluorescents.

Which came to something over 1.4kW, not counting the patio or shed lights.

What I did

The big constraint was that I didn't want to take down any ceilings or do anything structural. The following doesn't follow the order I did things in at all, and also elides some missteps where I installed or bought the wrong equipment.

1. The 40 watt GU10 halogens in the hallway were replaced with 4 watt LEDs (£15 for five). These are not as bright individually, but with five lights working instead of three the resulting light is just as bright and more evenly distributed. Score: -100/-180 watts, 120% quality.
2. I removed the dimmer switch in the dining room, replacing the four (buzzing) 20-60 watt transformers with a single 48 watt transformer and a wireless dimmer, and the twelve 20 watt halogens with 3 watt "daylight" disk LEDs (270 lumen each). The result is noticeably brighter, probably because the disc LEDs throw all their light downwards and don't waste any of it upwards or sideways, and provides a good light for reading or working. Score: -200 watts, 200% quality.
3. The sitting room followed the dining room, except that the transformers were only accessible through the narrow light fitting holes in the ceiling. This meant no wireless dimmer could be fitted in. Score: -140 watts, 80% quality (brighter, but losing the dimming is unfortunate).
4. The kitchen was easy, if not entirely satisfactory. I put in four R63 11 watt compact fluorescent bulbs. These are not quite as bright as the older 60 watt halogens (or 42 watt "eco"-halogens) and take quite some time to reach full light output. One advantage is that they aren't as glary as the halogens were. Score: -200 watts, 70% quality. (The light fittings are also ugly-as, so I'm thinking of replacing these with LED downlights.) Update: One of the CF bulbs blew, so I replaced it with a 7.5 watt LED bulb. This is brighter and starts up much faster; four of these would make this much better than the original halogens, say 120%.
5. I replaced the 35 watt GU10s in the breakfast room with 6 watt dimmable LEDs. These are more narrowly focused and don't provide as even a light. Score: -115 watts, 80% quality. (I think alternative wider-angle GU10 LEDs would improve this.)
6. I replaced the MR16s in the bathroom with 4 watt "warm" high power LEDs (with three individual LED drivers replacing the dead transformer). These match the 20 watt halogens very closely, for beam angle and colour and brightness, and five of them is plenty in the bathroom. Score: -80 watts, 110% quality.
7. I replaced the 50 watt MR16s in the study with "9 watt" (actually 5 watt) warm white LEDs. These aren't as bright and are a bit more narrowly focused. Score: -170 watts, 70% quality. (If I can fit larger holes into the ceiling, putting in dimmable LED downlights here would be good.)
8. I replaced the MR16 in the ensuite with a 4 watt "daylight" high power LED. And put a new "daylight" 10.5 watt LED in the shower. Score: -5 watts, 150%.
9. I replaced the party lights around the patio with twenty LED party lights. Score: -150/-570 watts, 200% quality.

If we turn on every light in the house now, that would come to maybe 300 watts in total, at least nominally. (In practise the transformers add some power consumption on top of the rated light power consumption, so this might be more like 400 watts in practice; I haven't actually tried the experiment yet.)

How much did it cost?

None of the components were expensive: LEDs have really dropped in price and I bought a lot of them off ebay - the 4 watt MR16s in the bathroom, for example, were only £11 for four. Of course the cost of the electrician for the bits that involved rewiring has to be added to that. Even so, I estimate the "pay back" time for the whole switchover at two years at the most. Our household electricity meter arrived only a few days before the major conversion started, back in November, but we clocked a few 18kWh days. Since then, we've averaged 11kWh/day over the darkest part of the winter. Which is maybe 80p a day in electricity saved, though that will be less in summer.

Some of these changes were relatively involved, but some of them are quite straightforward. If you have 20 watt or 35 watt halogens in GU10 or MR16 fittings, and they aren't on a dimmer switch, you can probably just swap them for equivalent LEDs that draw a fifth the power, without changing transformers or needing an electrician. The pay-back time on this could be very short, depending on how often they are used.

Other lights

We had three bedside and standing lights, with 20, 25 and 40 watt halogens in E14 and B22 sockets; I replaced these with 2.5 and 1.5 watt LEDs (about £3 each). Given how cheap LED lights are now, it's shocking that IKEA still sells desk/bed lamps with incandescent bulbs in them.

To provide the option of a warmer, dimmable light in the sitting room, I bought a "mother and child" uplighter/reading light combination. The uplighter of this had a 230 watt R7s J118 linear halogen, producing something like 5000 lumen - enough to light the room up quite decently just by reflection off the ceiling, thought that's probably the most insanely inefficient way of doing that. I replaced that with a 10 watt LED: this is only 900 lumen, but sends all its light upwards and is fine for mood lighting. If we want the room bright, the nine 3 watt disc LEDs in the roof will be plenty. The only halogen left in the house is the dimmable 40 watt G9 in the "child" reading lamp part of this light, for which I have been unable to find a replacement.