How Battery TOU Arbitrage Works in Arizona
Time-of-use electricity pricing creates a daily opportunity for home batteries. Arizona's two largest utilities — APS and SRP — both charge significantly more for electricity during peak afternoon hours than during off-peak hours. A home battery charges when electricity is cheap and discharges when it's expensive, pocketing the spread on every cycle.
On APS Saver Choice Plus, the summer arbitrage spread is the gap between the super off-peak rate ($0.0935/kWh, 10am-3pm) and the peak rate ($0.3439/kWh, 4-7pm) — a spread of $0.2504 per kWh. A 13.5 kWh Powerwall cycling at 90% round-trip efficiency delivers about 11.5 kWh of peak-rate electricity per day, which adds up over 365 days.
On SRP, energy rates are lower but SRP adds a demand charge — a per-kW fee based on your highest single on-peak hour. At $14.5/kW in summer, a battery that shaves 2-3 kW off your measured peak can save $348-$522/year in demand charges alone, on top of the energy arbitrage. This makes batteries particularly valuable for SRP customers with high AC loads.
The Arizona Incentive Stack
Three incentives reduce the upfront cost of a home battery in Arizona:
- Federal Investment Tax Credit (30%). Standalone batteries (no solar required) qualify for the 30% ITC through 2032. For a $12,825 Powerwall 3, that's $3,848 back on your federal taxes. This is the single largest incentive.
- Arizona Residential Energy Device tax credit (25%, capped $1,000). Arizona's state-level credit covers 25% of installed cost, but the cap means it tops out at $1,000 for most battery systems. It shares a cap with solar — if you've already claimed the solar credit in the same tax year, there may be nothing left for the battery.
- APS Cool Reward battery rebate ($3,750). APS offers this rebate to residential solar customers who add an approved battery system. SRP does not offer a comparable rebate as of 2026. This is the tiebreaker that makes APS battery economics slightly better than SRP for many homes.
APS vs SRP: Which Utility Makes a Battery Worth It?
The answer depends on your home. APS customers benefit from a wider energy arbitrage spread (the super off-peak rate is the cheapest electricity either utility sells) plus VPP earnings and the Cool Reward rebate. SRP customers benefit from demand charge shaving, which can be worth more than pure energy arbitrage for homes with high peak demand (central AC + pool pump + dryer all running at 5pm).
In general, payback periods are shorter on APS (thanks to the rebate and VPP) for homes with moderate demand, and shorter on SRP for homes with high peak demand spikes. Use the calculator above to model both utilities with your actual usage.
A Note on Tesla Referral Credits
If you order a Tesla Powerwall through a referral link, both you and the referring owner receive Tesla credits. The buyer gets $400 off their Powerwall purchase, and the referrer receives $250 in Tesla credits. These credits can be used for Supercharging or the Tesla online store — they cannot be applied to an auto loan or vehicle purchase. Our Tesla referral link is available in the related reading section below. Full disclosure: AZ Energy Hub earns Supercharging credits if you use our referral link, which does not affect your purchase price.
What This Calculator Does Not Include
This calculator models the financial value of TOU arbitrage, demand shaving, and VPP earnings. It does not assign a dollar value to backup power during outages — but that's a real benefit in Arizona, where monsoon storms knock out power for 4-12 hours several times per summer. If you've ever lost a refrigerator full of food or spent a night without AC in July, backup power has a value that doesn't show up in the arbitrage math.
The calculator also does not model solar self-consumption optimization. If you have rooftop solar, a battery lets you store midday production and use it during the evening peak window instead of exporting to the grid at the low export rate ($0.0760/kWh on APS). This self-consumption value can add $200-$500/year depending on your solar system size and export volume — use our Solar ROI Calculator to model this.