Why Your Utility Matters for Solar ROI
APS and SRP serve different parts of the Phoenix metro area, and their rate structures create meaningfully different economics for solar and battery owners. The two biggest differences:
- Export rates. APS pays $0.0760/kWh for solar exports — about 117% more than SRP's $0.035/kWh. Every kWh you push to the grid is worth more on APS.
- Demand charges. SRP charges $14.50/kW in summer for your highest single on-peak hour. APS has no demand charge. This means on SRP, one hour of running central AC + pool pump at 5pm can add $100+ to your monthly bill — even if solar covered most of your energy usage.
When APS Wins
APS is generally better for solar-only systems (no battery) because the higher export rate means more value for every kWh your panels overproduce. APS also wins when you add a battery, thanks to the $3,750 Cool Reward rebate and VPP earnings ($150-$500/year). The arbitrage spread on APS is also wider: super off-peak at $0.0935/kWh vs peak at $0.3439/kWh is a $0.2504 spread.
When SRP Wins
SRP can win for large homes with high peak demand that add a battery. The demand charge shaving value of a battery on SRP ($348-$522/year for a 2-3 kW reduction) can outweigh APS's VPP and rebate advantages. SRP also has lower base energy rates, so if your solar covers nearly all your energy needs and you have minimal exports, SRP's lower consumption cost tips the balance.
The Battery Makes Everything Better
On both utilities, adding a battery improves the solar ROI dramatically. Without a battery, about 65% of your solar production gets exported at the low export rate. With a battery, you self-consume ~70% and shift your peak usage to off-peak — the combined effect adds $500-$1,500/year to your savings depending on system size and utility.
For more detail on battery-specific economics, use our Powerwall Payback Calculator which models incentive stacking, VPP earnings, and demand shaving in depth.
How This Calculator Works
This calculator runs identical solar + battery math against both APS Saver Choice Plus and SRP E-27 rate structures, then compares the results side-by-side. For each utility:
- Annual energy cost: Your monthly kWh split across peak/off-peak/super-off-peak windows using the same usage profile, multiplied by each utility's published 2026 rates.
- Solar savings: Your system's annual production (from NREL PVWatts for Phoenix) × self-consumption value + export value at each utility's published export rate.
- Battery savings: TOU arbitrage (charge cheap, discharge expensive) + APS VPP earnings + SRP demand charge shaving. Each utility has different levers.
- Incentives: Federal 30% ITC, AZ 25% state credit (capped at $1,000), APS Cool Reward $3,750 rebate (APS only). Applied to net cost to calculate payback period.
The “winner” is whichever utility produces a shorter payback period and higher lifetime savings. All rates from published 2026 tariffs. Solar production from NREL PVWatts v8 API for Phoenix, AZ.