Just a thought I had whilst wasting time at work...


If you were to build a new house... The brief of the house is to be as environmentally friendly and cheap to run as possible (even if it means build cost might be slightly higher)

Would it make sence to fit a 12 or 24V DC sockets in every room... That way you could run LED lights to provide very cheap lighting... and could bin all of those tiny little transformers for everything and simply have a smaller transformer to step it donw from 12/24 to whatever the item needs.... (thinking 5v for phones, 15v for laptops etc)

The 12/24V DC system could be powered from large batteries charged partially via solar power and partially by a decent efficient mains powered transformer type control unit...

Would it make any sence to do that?

I can see it being particularly useful for light fittings/standard lamps etc provided decent LEDS are available which I am sure they are....

It just seems daft having everything in the house drinking 230V when the actual item only really needs 5 or so

(I was also toying with the idea of having rainwater harvesting tanks to feed the toilets.... )

[Edited on 26/1/09 by tegwin]

an interesting idea, but for phone chargers, they come with phones from 240v down to 5v or whatever, so if you have 12v sockets, you'd need another transformer anyway, and where would you buy it from?
you could have 12v lighting circuits i guess, but i think LED lights would be a bit cold and clinical

if you have a wind turbine too , it would be more efficient without having to invert it . you could trickle charge batteries .

im currently designing a wind turbine .

whats your objective here?

See what frustrates me is people not seeing the biggest picture. For example, my old washing machine isn't very efficient so i'll replace it - the cost of extracting the raw materials, making them into the material you want, shaping it, shipping it, storing it, producing a shop etc etc etc is HUGE.

Anyway, back to the point.

If you where going to do this seriously i'd look at fitting USB sockets around the house. Lots of things take the 5v USB connection and use that to power the device so it may work. I'm not convinced that its really a great idea though. If you ignore the losses at power station generation - what is the loss of a transformer? Eg if it provides 5w of power, does it consume 5.2w or 20w?

Also bear in mind standards change - so in 10 years time your 5v DC lines may be redundant as most things are 3v with a specific plug.

240v AC seems to be with us for a while.


Having said all that i FULLY commend your thinking.

There are now 230v LED's on the market which are quite good.
The problem I see here is that to get the required light output you will have to use the same amount of energy as the 230V LED's. The only benefit really being the much safer lower voltage. If you use 12v LED's you would possibly have to upgrade the cables as the 12V's will have to draw more current to provide the light output. Also ,although maybe not as big a deal in a small house, if you plan on putting the lights in the same place as you normally would, the length of cable used is quite a lot and you are likely to experience voltage drop due to the 12v supply not being able to overcome the resistance of the cable as easily as 230v. Again cable sizing will need to be upgraded to overcome this.

In other words lowering the voltage will not mean the power stations will have to burn less oil, and it does not mean that solar panels produce 12 volts easier than 230v. It is how the energy is used. Make all items use less energy to save the planet.

[Edited on 26/1/09 by quinnj3]

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Originally posted by blakep82
an interesting idea, but for phone chargers, they come with phones from 240v down to 5v or whatever, so if you have 12v sockets, you'd need another transformer anyway, and where would you buy it from?

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You can already buy 240V LED bulbs that just screw into your light sockets. Low power ones for the moment but the electronics trade press are saying that more are on the way this year. You can also choose your shade of white, so softer whites in bedrooms and lounges but daylight white in kitchens and studies.

BTW, your plan of designing in econess is spot on. I had quotes for solar hot water to be installed in my house last year. Estimates ranged from £12,000 to £20,000 and that was with pipes laid on top of the existing plaster. I pointed out that the whole kit and kaboodle could be bought as a DIY package for about £2000 and he looked, well, offended. Especially when I said the parts were a higher spec than he was offering. The cost to fit that to a house during its construction would be much less than retrofitting it. Same would go for solar PV panels and low voltage wiring.

it would be worthwhile having a 12v light system, but i dont think you would want lots of sockets at 12v. Maybe have a charging point that had a 240v inverter running off the 12v batteries. It really depends on how much 12v juice you can make on site, ie wind potential or roof space if you think panels are the way forward.

You could have waterwheels in your downpipes

The cost of fitting of those solar panels is scandalous. It would be cheaper to get plumbers from Northern Ireland to do the work. It would be carried out to the same standard and only cost a total of about £5000 including paying the extra to put the tradesmen up for a few nights. I'm building a house at the moment and was quoted £20000 for a ground source heat pump,solar panels and all my domestic plumbing, all high quality parts. I still see that as over the top. I reckon I could get if for around £17000.

Hmm... Yes, I had not thought through the resistance in the cables... Was just one of those passing thoughts...

This would be the second project using "alternative" heating methods..... but I would like this one to be a purpose built house to make the most of it..

Ground loops in the foundations, Solar cells on the roof feeding a thermal store supplying direct hot water and underfloor heating...

With a clever zoned computer controled system I recon it would be quite good...


Its just trying to think up other ways of saving energy...

I couldnt give a toss about the planet.... all I care about is reducing my electricity/gas/water bills etc

While I was over there I was told there are a lot more house fires in the US caused by wiring due to their using 110v so twice the current for the same power.

If you're piping 12v DC around you'll need more than just a transformer to change voltage for laptops etc as transformers only work on AC.

i think that if you just want to reduce your energy bills, insulation and careful driving is the way forward. It would be far more effective than free lighting.

Ive come downstairs and put the toaster and gas fire on. Really, i should have cold breakfast and put a jumper on if i wanted to save money.

having a separate low voltage supply may have its uses.

let's say you decide on 12 V DC because that is what car batteries provide and you can get solar cargers to keep them topped up.

you can buy drivers that run off a voltage range that supply the exact amount of power to a LED - these are more efficient than drop resistors. I am using such a set up for my DIY lamps.

A lot of stuff can run off 12 V and if you want to power something at a lower voltage, then you can by regulators.

you would need to think about the cable current rating.