Another approach is to go for specific task load shifting and a specific battery sized to suit. Since lithium is small and light it can be packed with a timer system and inverter and mounted next to the appliance socket (in a cupboard in many cases).
e.g say the fridge draws less than 200w and 1kwh per day, one could load shift say around .5 kwh per day. A Thundersky 12v 40ah battery with a small inverter etc. could probably be rigged up for around $400 total?
http://www.evworks.com.au/index.php?category=5
Then load shifting by charging the battery plus running the fridge during the day, switching to battery power at night, say 32c *.5 =14c per day return (to take some losses). Then simple payback is after 2800 days or 7.7 years. During that time you have had UPS protection and/or an alternative small power supply for 12 or so hours if the power supply fails. (not exactly UPS, since it would depend when power failure occured)
If the lithium battery lasts 4000 cycles, which literature indicates is possible?, then you can come out ahead but it's not a huge financial return but at least it's not a loss like the more expensive systems would be. I also think it's not good for the environment since batteries are toxic from go to whoa.
In any case that approach could be effective for most predictable daily loads like freezer, tv/entertainment system, solar hw pump , pool pump etc.
Time of use tariffs may also enable some better returns.
If lithium batteries come down a little bit in price it would obviously become well and truly feasible I think. Bear in mind it's just a thought experiment, I have not done any of it and so I don't know what practical problems would arise.
Posted Sunday 4 Nov 2012 @ 5:23:34 am from IP
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