The economics of battery storage just received triple-whammy benefits for APS customers in Arizona. The Utility is offering a $2,500 rebate for a minimum 5 kWh battery. The only requirement is that APS receive data associated with battery usage. There is an additional rebate of $1,250 available, but then you turn over control of the battery up to 100 times per year for the Utility to manage the stored power to their benefit. Not recommended.

Over the last month, APS has been converting time-of-use customers over to a new mandated plan. The peak power period is now 4 PM to 7 PM on non-holiday weekdays, year-round.  The previous period was 3 PM to 8 PM. We have the Arizona Corporation Commission to thank, as they believed that the five-hour period was too hard on families and required APS to go to three hours.

To balance the revenue books, the Utility increased the $/ kWh pricing for the non-demand electricity plan by 26% during peak periods and 2.5% during non-peak. All these changes result in a smaller battery size required for peak power shaving and larger savings per kWh of battery power used in lieu of APS peak power consumption.

Now property owners also choose to install batteries to ensure that essentials like lights, AC, refrigerators and freezers continue to run in the event of a power failure. The size of the battery system required will very much depend on the amount of electrical energy the owner anticipates needing to carry them through an overnight outage.

For Valley residents, the worst-case scenario is losing power during the summer when at least running the property’s smallest AC unit would be necessary to remain. For a multi-day outage, the solar electric system must be capable of providing sufficient electricity for daytime consumption plus excess generation to completely recharge the batteries and run off of them at night.

When living off-grid, battery storage is an essential component to complement solar electric generation. Many choose to run lights, appliances and AC units that use DC current, compatible with the electricity produced by the solar panels and stored by the batteries, eliminating the need for an inverter and losses associated with converting DC to AC electricity.

With further improvements in battery technology and reduction in storage costs, it is expected that batteries will become the preferred economic storage method for excess solar electric production within the next 10 years. This is the same period of time in which new solar customers of APS are guaranteed their buy-back rate for excess solar power delivered to the grid.

Even if you choose not to go with battery storage today, ensure that your solar electric system is compatible with the future installation of backup batteries.