SRP Solar: Demand Charges, E-27, and Why Batteries Dominate the Math

How SRP treats rooftop solar in 2026

SRP is an agricultural improvement and power district, not an investor-owned utility. Its rates are set by the SRP elected board rather than the Arizona Corporation Commission. In early 2015, the board voted to move new rooftop solar customers onto the Customer Generation Price Plan (E-27), which swapped the old net-metering math for a three-part bill: a basic monthly charge, a modest energy (kWh) charge, and a substantial demand (kW) charge on the single highest 30-minute grid pull during on-peak hours.

SRP has refined the design several times since, and as of 2026 the solar portfolio includes E-27, E-13, E-14, E-15, E-28, and E-21. Every option available to new solar customers is some flavor of demand or time-of-use pricing. There is no flat-rate plan offered to new rooftop PV customers. See SRP solar pricing plans.

SRP customer generation rate plans

Plan	Energy charge	Demand charge	When it makes sense
E-27 Customer Generation	Modest kWh rate, seasonal TOU	$25-$35/kW summer on-peak (single highest 30-min)	Battery-equipped homes with disciplined load control
E-13 Price Plan for Solar (TOU Export)	TOU energy, no demand	None	Solar-only homes with strong midday export; high on-peak kWh cost
E-14 Electric Vehicle	Super-off-peak EV rate overnight	None on EV plan; paired with E-27 when solar present	EV households that charge after 11pm
E-15 Time-of-Use Export	Seasonal TOU, export credit on kWh sent back	None	Smaller solar systems, no battery, moderate use
E-21 Average Demand	Flat kWh rate	Average demand over the month, not single peak	Customers whose peaks are hard to control but whose averages are low
E-28 Customer Generation EV	Combines E-27 and EV overnight	Same on-peak demand window as E-27	Solar plus EV plus battery, most common 2026 stack

Source: SRP Residential Price Plans.

SRP demand charges explained

On E-27 and E-28, SRP measures your highest 30-minute average grid import during the on-peak window (3-6pm weekdays, May through October) and bills that single reading at the summer on-peak demand rate. In 2026 the summer on-peak demand tier is roughly $25 per kW for the first 3 kW, stepping up to roughly $33 per kW for usage above 10 kW. Winter demand rates are lower but the mechanic is identical.

Concrete example: a 4-ton AC at 4.5 kW plus a pool pump at 1.5 kW plus a range at 4 kW running concurrently for 30 minutes on a July Tuesday at 4:30pm gives you 10 kW of demand. At the middle tier that single half-hour costs roughly $300 on the next bill. A homeowner who pre-cools the house at 2pm and then runs minimal load during the demand window can keep that reading under 3 kW and pay around $75 instead.

This is why solar-only on SRP E-27 underperforms expectations. Solar typically peaks between 11am and 2pm; on-peak demand is measured from 3pm to 6pm, when panel output is dropping and AC load is rising. Panels alone do not solve the demand problem. See SRP residential pricing sheets for current kW and kWh tiers.

Where battery storage cuts SRP bills

A correctly sized battery dispatched to cover the 3-6pm window is what makes rooftop solar viable on SRP. The goal is not full off-grid operation; it is keeping the single 30-minute demand reading low during five specific weekday hours, May through October.

Common 2026 options:

• Tesla Powerwall 3 13.5 kWh usable, 11.5 kW continuous, one unit typically enough to cover 3 hours of a 4-ton home with normal use.
• Enphase IQ Battery 5P 5 kWh usable and 3.84 kW continuous per unit. Most SRP households need three units to match the continuous output a 4-ton AC plus household loads require during the demand window.
• Franklin aPower 2 15 kWh usable, 10 kW continuous, grid-forming, a common alternative when a customer needs higher usable capacity per unit.

Installers programming for SRP should set the battery to target zero grid import from 3:00pm to 6:00pm weekdays, with a floor that preserves 20 percent of capacity for unexpected loads after 6pm. A well-tuned battery can cut an SRP E-27 summer bill by 40 to 60 percent relative to solar-only on the same plan.

SRP interconnection and timeline

SRP interconnection runs 20 to 30 days from complete application to permission to operate, faster than APS on average. SRP requires all equipment to be on its approved inverter and battery lists. Tesla Powerwall 3, Enphase IQ 5P, Franklin aPower 2, SolarEdge Home Hub, and most major manufacturers are on the list, but double-check the specific model number and firmware before signing a contract.

The installer must hold the appropriate Arizona Registrar of Contractors license (commonly ROC KA or ROC C-11 for PV). SRP does not require the installer to be a utility-partner contractor, but it does require submittal of line diagrams, inverter datasheets, and (for battery systems) an energy storage interconnection application. SRP swaps the meter as part of the PTO visit at no additional customer cost.

SRP Battery Demand Management (status 2026)

SRP historically offered a Battery Demand Management pilot that paid participants up to $250 per year in bill credits for allowing SRP to dispatch their battery during grid-stress events. Enrollment has opened and closed in waves. Confirm current program status on the SRP website before assuming it is available. If enrollment is open, it stacks with the federal ITC and is structured as a bill credit rather than a rebate, so it is not taxable at install.

SRP federal and state incentives

SRP customers stack the same federal 30 percent Residential Clean Energy Credit (IRC Section 25D) and the $1,000 Arizona state tax credit as any other AZ homeowner. Standalone battery (no solar) qualifies for the federal credit as of tax year 2023 under the Inflation Reduction Act. See Arizona solar incentives for the full stack.

For system cost and financing, see Arizona solar cost. For batteries specifically, review Arizona solar battery options and the Tesla Powerwall Arizona guide. Panel specs and manufacturer comparisons live on solar panels in Arizona.