Well, I'll give you my take on low energy fridges.
Where does the extra energy go?
Into heating my house. OK I am paying 6p a Kw/h as against 2.5p for oil, but its not a net total loss.
So every bit of energy efficient electrical stuff has to have the so called gains offset by the amount of oil LESS I burn to keep warm.
Its the same with 'we could save the country XXX by half filling the kettle'
No, we could save the country about .6 of X at best.
In terms of boiler replacement, its an easy calculation. 2% off you energy bill for what - a couple of hundred quid.
In terms of e.g. double glazing its a phenomenal con. DG alone (if you remove the dramatic effects that sealing windows properly has on heat loss) never ever pays for itself, unless you have HUGE windows.
Floor and wall insulation is very marginal when fitted post build due to the expense of doing it - apart from dry lining which is very cost effective.
Only loft insulation is simple and cheap enough to do to be a complete no brainer for any householder.