Thursday, 15 December 2016

How cheap does storage need to be?

When I mention domestic demand response I increasingly hear storage as being the solution.
But how cheap does storage need to be to break even? Turnkey solutions at the moment cost around £500 per kWh. To get the cost down to a retail price of domestic electricity of 12p/unit, each kWh of storage would need to be used around 4000 times, that's once a day every day for 11 years. 
So:
  • The battery and equipment would need to last for 4000 cycles before it broke even.
  • If it did, the minimum time to break even is 11 years.
  • This assumes the electricity going in to the battery is "free" i.e. from a PV installation where no other use for the electricity can be found.
In practice the load factor would be much less than 100% on a daily basis, thus reducing the returns further.

The price would need to at least halve to get any chance of a six year payback, which is what was needed from FITs to get mass PV installation going.

Do batteries last for 4000 cycles? 500-1000 cycles is more typical for lead acid.

Why not just shift the time at which you use electricity - it's virtually free to do so!