How do APS and SRP battery storage and demand response programs work for Arizona homes?

APS and SRP battery and demand programs all work off the same idea: power costs more during the late-afternoon and evening peak, so anything that lets your home pull less from the grid during those hours saves money. The two big Arizona utilities run different versions of this. Both use time-of-use rates and demand charges that make peak-hour power expensive, which is what makes a home battery pay. You charge the battery from solar or cheap off-peak power, then discharge it during the costly peak window so you buy little or no grid power then. On top of that, APS runs a Storage Rewards pilot that pays you to let it pull from your battery during grid events. SRP, which sets its own rates as a public power provider, rewards the same off-peak shift through its demand and time-of-use plans. The U.S. Department of Energy calls this whole approach demand flexibility, the ability of a building to reduce or shift electricity use when the grid is stressed.

Here is how time-of-use and demand rates work, how a battery earns its keep against them, what the APS Storage Rewards pilot pays, and how APS and SRP differ.

Time-of-use and demand rates: why peak hours cost more

Time-of-use and demand rates both raise the cost of power during peak hours, but they do it in two different ways. A time-of-use rate charges more per kilowatt-hour during a set on-peak window and less off-peak. The bet is simple. Run your dishwasher, pool pump, and EV charger off-peak, and you pay the cheaper rate. APS sets its on-peak window for many plans at weekday late afternoon and early evening, the hours when air conditioning demand across the desert is highest.

A demand charge is different and trips up a lot of homeowners. It bills you for your single highest spike of power draw during peak hours, on top of the energy you use. On the APS Time-of-Use plan with a demand charge, "the monthly demand charge is based on your highest hour of energy used during on-peak hours (4pm-7pm weekdays) each billing month." Run your AC, oven, dryer, and EV charger all at once during that window one afternoon, and that one hour sets a charge for the whole month. The fix is to stagger big loads so they never stack into a single peak-hour spike.

Both rate types reward the same behavior: move your heavy use out of the late-afternoon peak. That is exactly the gap a home battery is built to fill.

How a home battery earns its keep against those rates

A home battery earns money against time-of-use and demand rates by discharging during the expensive peak hours so you buy little grid power then. The strategy is called peak shaving. You fill the battery when power is cheap or free, from rooftop solar during the day or from off-peak grid power overnight, then draw the home off the battery during the costly peak window. During those hours the meter barely moves, so you dodge the high time-of-use rate and flatten the demand-charge spike.

In Arizona, solar makes this especially effective. The sun is reliable, so a solar-charged battery refills nearly every day and is full and ready by the time the late-afternoon peak hits. SRP, the public utility serving much of the East Valley and parts of the metro, frames the fit plainly in its own guidance: batteries let customers store unused energy to use after the sun goes down, which suits time-of-use, customer generation, and demand price plans, and battery storage helps manage on-site demand through peak shaving. That is the same logic on the APS side.

A battery also adds backup power when the grid drops, which matters during monsoon outages. For the backup-power comparison, see our generator vs battery backup page, and for whether to add the solar that charges it, our solar on new construction page. The cleanest time to wire for all of it is during the build, covered in our solar and battery pre-wire page.

The APS Storage Rewards battery pilot

The APS Storage Rewards pilot pays you to share your home battery's stored energy with the grid during high-demand events, on top of the savings the battery already gives you. It is a pay-for-performance program, meaning you earn based on how much power you actually contribute. APS states a participant can "earn $110 per average kW you contribute from your battery" across the event season. To join, you must be an APS residential customer on a residential rate plan with "an eligible battery storage system operated by an eligible manufacturer," and the battery must have "Permission to Operate (PTO) from APS prior to enrolling."

The events are limited and you stay in control. They run "from May 1 through October 31," with "up to 60 events" that occur "only between 4 p.m. and 10 p.m." during times of high energy use, which lines up with the summer evening peak. During an event, "your battery manufacturer will signal your battery system to release stored energy to your home and send any remaining energy to the grid." APS gives "advance notice by email or text with the date and time," and you can "opt out of an event at any time." So your battery is yours first, and the program taps it only during the hours the grid is most stressed.

This is a small-scale version of what the industry calls a virtual power plant, where many home batteries are pooled to act like one grid resource. The Department of Energy promotes this kind of demand flexibility, where buildings respond to grid needs while cutting their own energy use. Because it is a pilot with set payments and eligibility, confirm the current Storage Rewards terms, payment rate, and eligible battery list directly with APS before you count on it (figures as of June 2026).

How APS and SRP differ, and why it matters

APS and SRP differ in who regulates them, which shapes how their rate plans and battery programs are set and changed. APS is an investor-owned utility regulated by the Arizona Corporation Commission (ACC). The ACC reviews and approves its rates and programs in public rate cases, so APS plans like the demand-charge time-of-use rate and the Storage Rewards pilot are set under Commission oversight. SRP is not. The ACC states plainly that "the Salt River Project (SRP) is not under the jurisdiction of the Corporation Commission for rates, rules and regulations," because SRP "became a political subdivision of the state of Arizona and is designated as a quasi-municipality" under the Federal Reclamation Act of 1902. SRP's elected board sets its rates and plans directly.

For a homeowner, the practical differences are these:

• Which utility serves you depends on location. Much of Scottsdale, Phoenix, and the metro is APS or SRP territory depending on the parcel. Cave Creek, Carefree, and Fountain Hills areas vary. Confirm your specific address before you design around a program.
• Plan names and windows differ. APS uses a 4-to-7 p.m. weekday peak on its demand plan. SRP runs its own plans, such as plans that target 5-to-10 p.m. or 6-to-9 p.m. peak windows. The exact hours decide when your battery should discharge.
• Battery incentives differ. APS runs the Storage Rewards pay-for-performance pilot. SRP offers its own solar, demand, and export-based plans for customers with on-site generation and battery storage. Check each utility's current offer for your address.

The bottom-line answer is that both utilities make peak-hour power expensive, so a home battery pays by shifting your use and your solar energy into those hours, and APS will also pay you to share battery power during grid events. Rates, peak windows, and program payments change often and are set by the ACC for APS and by SRP's board for SRP, so confirm the current plan, peak hours, and battery incentives with your specific utility before you size a system. For how the battery load fits your panel, see our electrical service size page.

Building with Jematell Homes

Desert-smart design and systems are standard on every home we build. Every project is different, so we will confirm the specifics for your parcel and budget with you directly.

Sources

• APS Storage Rewards Pilot Program
• APS Time-of-Use 4pm-7pm Weekdays with Demand Charge service plan
• Arizona Corporation Commission: Utilities FAQs (jurisdiction over APS; SRP not regulated)
• U.S. Department of Energy: Grid-Interactive Efficient Buildings (demand flexibility)