Roger Mills wrote:
In an earlier contribution to this discussion,
The Natural Philosopher wrote:

I would simply LOVE a system that when its cold and wet and the trees
take out a power line, did not require me to have to fiddle around
starting up motors and rewiring the house..to get the TV and the
lights back on. Cooking we can do on te aga...and having te oil
boiler work would be fine..

AND if it almost paid for itself by using off peak electricity
overnight to charge batteries I ran off during the day, it would be
magic.

Anyone know what the efficiency is likely to be of going mains--battery
charger--battery--inverter--mains?


mm..probably around 90% each way. Say 81%


In other words, how many kWhs need to go into the charger to get 1kWh out of
the inverter?

As long as the overall efficiency is better than about 50%, you *could* be
better off by buying all your electricity at the off-peak rate and storing
it in batteries - but you'd have a hell of a capital investment (and
probably maintenance/replacement costs) to contend with.

Well I reckoned about 5 grand..batteries SHOULD do what? 10 years? Hmm.
Not as attractive as I thought ;-)