My adventures over the last few years in low power computing has thrown up some interesting maths.
I won't bore you with the details but this winter we have saved about £40 over last winters bill. If that keeps up, that will be a £160 saving in the year; roughly an eighth shaved off our electric bill. And there are yet more bulbs to be replaced and our big CRT TV has yet to be changed out.
I don't know if all that is attributable to the drop in PC consumption from three full sized machines being on all the time, to four lower power units totalling less than 200 watts between them, or the couple of compact fluorescents that have been replaced with LED bulbs.
All I can say is that in a domestic environment, when push comes to shove, the big ticket items like washing machines, fridge freezers, electric hobs and heating systems are always going to be the big energy eaters and all the lagging and cavity insulation isn't going to have much bearing on the number of times you wash your clothes, have a shower, cook dinner or how much food you decide to keep on ice.
To that extent, replacing the light bulbs and going for low power computing is going to play its part, but it isn't going to break the back of the electric bill.
It clearly has its niche, however. As the months have gone on, manufacturers have been hard put to match the performance delivered by the latest ARM chips. They've shaved nanometres off their fabrications and in the process, lowered the power consumption of their latest chips.
The A10 I'm using positively sings for low powered gaming and even that isn't the latest technology but it, the motherboard and 8 gig of RAM were mine for less than £250 which is less than I'd have paid for that kind of technology a few years ago because Radeon graphics are built in to the processor die itself.
It is a no brainer that as we change out our machines, we should be considering low power equipment in its stead. They'll deliver us better consumption and lower heat generation which means less fans needed and less noise in our lives on top of lower electricity bills.
2013 will be a year where low power computing finally delivers performance 64 bit processors (we already have some that I don't think are ready for general use yet) and low power solid state drives that all work from external power supplies and use heat sinks to get rid of the little that is generated.
Low power computing does pay, but forking out cash ahead of the upgrade curve probably won't pay for itself IMHO.