DNAinaGoodWay wrote:Even without solar, if you could charge them at super off peak rates, and use that energy during peak rate times, they could pay for themselves.
Could it? Let's say that the battery in a 1.2 kWh module costs $300 ($250/kWh) and the inverter costs $100 for a total of $400. I think this price is probably low, but let's go with it.
Let's say that the battery is designed to last 10 years, but let's ignore capacity loss over time and let's also assume that the inverter is 95% efficient so your round trip efficiency is 90%.
We're also going to assume that you can get a full cycle of the battery every day, 365 days/year and that there are no vampire losses on the unit and that you don't have to worry about interest or anything on the money used to buy the battery.
That gives you 3650 cycles to recoup your investment of $400, over 10 years which means that you need to net $0.11 / day.
Taking into account 90% round trip efficiency, that means that you have to sell each kWh at a profit of at least $0.10 to break even.
Here in San Diego under SDG&E on either EV-TOU2 (whole house EV) or the DR-SES (solar net metered), this is currently not possible during the Winter (Nov-Apr) TOU rates - the spread between off-peak and peak rates is only $0.03 / kWh at the most. In the summer (May-Oct) there's about a $0.30 spread between peak / off-peak rates. So you might make $60 / year here in San Diego getting you to break even some time after 6 years. If the utility lets you install them and use the grid to charge the batteries (the utility is very reluctant to do so).
That's an optimistic scenario. In the majority of the country there will be no economic incentive to install these unless they can also provide backup power when the grid goes away completely.
Storage does open up a lot of opportunities for load shifting. For EV quick charging this is absolutely necessary to make economic use of the grid - just look at how Tesla is moving to install grid storage at each of it's Superchargers, especially in states with high demand charges.
In the short term I think it's quite possible that the utility company will look to using these for demand response, frequency regulation and reactive power support. If the system is designed to be remotely controlled by the utility, it's possible that 1.2 kWh of storage could provide a lot more value to the utility than the energy value alone. But the big issue again is that I feel that 1.2 kWh building blocks are too small to be economical.
BTW Reg - insightful post there a couple posts up.