SRP Solar: The Honest Truth
Salt River Project (SRP) serves over 1 million customers in the Phoenix metropolitan area. Unlike most utilities, SRP is a political subdivision of Arizona—not regulated by the state utility commission. This means they set their own rules, and those rules are unfavorable to rooftop solar.
Net metering: No traditional net metering
Export rate: ~$0.02-$0.04/kWh (extremely low)
Demand charges: Yes, significant
Solar rating: ⭐ Difficult
Battery value: Essential to make solar work (Source: utility tariff filings and DSIRE Database)
The bottom line: Solar with SRP is challenging but can still make sense with the right strategy. You need to understand demand charges, size your system carefully, and likely add a battery to make the economics work.
Understanding SRP Demand Charges
Demand charges are the reason SRP is difficult for solar. Unlike most utilities that charge only for energy (kWh), SRP also charges for your peak power usage (kW) in a month.
How Demand Charges Work
SRP looks at the single highest hour of electricity usage in your billing period and charges you based on that peak. Even if it only happens once, you pay for it all month.
| Example Scenario | Without Solar | With Solar (No Battery) |
|---|---|---|
| Peak demand (kW) | 8 kW (AC + appliances) | 8 kW (evening, solar not producing) |
| Demand charge rate | $13-$20/kW | $13-$20/kW |
| Monthly demand charge | $104-$160 | $104-$160 (same!) |
Demand Charge Rates by Plan
| Rate Plan | On-Peak Demand | Off-Peak Demand | Peak Hours |
|---|---|---|---|
| E-27 (TOU w/ demand) | $13.95/kW | $5.84/kW | 3-8 PM weekdays |
| E-26 (Solar customer) | $15.96/kW | $9.59/kW | 3-8 PM weekdays |
| E-15 (EV + Solar) | $16.14/kW | $7.71/kW | 4-7 PM weekdays |
SRP Export Rates: The Other Problem
When your solar produces more than you use, the excess goes to the grid. SRP pays you almost nothing for it:
| Time Period | SRP Export Rate | What You Pay for Grid Power | Loss |
|---|---|---|---|
| Super off-peak (10 AM - 3 PM) | $0.017/kWh | $0.06/kWh | 72% loss |
| Off-peak (other daytime) | $0.025/kWh | $0.08/kWh | 69% loss |
| On-peak (3-8 PM) | $0.035/kWh | $0.14/kWh | 75% loss |
SRP Rate Plans for Solar Customers
SRP requires solar customers to switch to a time-of-use plan with demand charges:
E-26: Standard Solar Plan
- Mandatory for new solar customers
- Demand charges apply
- On-peak: 3-8 PM weekdays (May-Oct), 5-9 AM & 5-9 PM (Nov-Apr)
- Lowest export rates
E-27: TOU with Demand
- Available to all customers
- Slightly lower demand charges than E-26
- May be better for smaller solar systems
E-15: EV + Solar Plan
- If you have an EV, this may save money
- Off-peak EV charging benefits
- Narrower peak window (4-7 PM)
Strategies to Make SRP Solar Work
Strategy 1: Add a Battery (Essential)
A battery is nearly essential for SRP customers. Here's why it transforms the economics:
| Benefit | Without Battery | With Battery |
|---|---|---|
| Demand charge reduction | None | 50-70% reduction |
| Export value | $0.02-0.04/kWh | Stored for self-use ($0.10-0.14 value) |
| Peak shaving | No | Yes (battery covers peaks) |
| Annual savings (7kW solar) | $400-700 | $1,200-1,800 |
| Payback period | 15-20+ years | 10-14 years |
Strategy 2: Right-Size Your System
With SRP, do NOT oversize. Every kWh you export is worth only $0.02-0.04. Size your system to cover 70-80% of your usage, and use a battery to store the rest rather than exporting.
Strategy 3: Shift Usage Patterns
- Pre-cool your home: Run AC hard from 12-3 PM when solar is producing, then coast through peak
- Run appliances midday: Dishwasher, laundry, pool pump during solar hours
- Smart thermostat: Program to reduce AC during 3-8 PM peak
- EV charging: Charge midday from solar or overnight
Strategy 4: Manage Demand Spikes
- Stagger appliances: Don't run AC, dryer, and oven simultaneously
- Watch your peak: One bad hour sets your demand charge for the month
- Battery peak shaving: Battery kicks in during high-usage moments
SRP vs APS: The Arizona Divide
Many Phoenix-area homes can't choose their utility, but if you're deciding where to live:
| Factor | SRP | APS |
|---|---|---|
| Net metering | No (export rates only) | Export rate ~$0.10/kWh |
| Demand charges | Yes, significant | Optional (some plans) |
| Solar friendliness | ⭐ Hostile | ⭐⭐⭐ Moderate |
| Battery value | Essential | Helpful but optional |
| Typical solar payback | 10-14 years (w/ battery) | 7-10 years |
Is Solar Worth It with SRP?
Honest Assessment
| Situation | Worth It? | Notes |
|---|---|---|
| Solar + battery, high usage (>$200/mo) | ✅ Yes | 10-14 year payback, good long-term |
| Solar only, high usage | ⚠️ Marginal | 15+ year payback, barely positive ROI |
| Solar + battery, low usage (<$150/mo) | ⚠️ Maybe | Math is tight, run specific numbers |
| Solar only, low usage | ❌ Probably not | Demand charges eat most savings |
| Environmental motivation + budget | ✅ Yes | If ROI isn't primary driver |
The Real Numbers
For a typical SRP home with $250/month electric bill:
- Solar only: ~$600-900/year savings, 15-20 year payback
- Solar + battery: ~$1,400-1,800/year savings, 10-14 year payback
Frequently Asked Questions
Why is SRP so bad for solar?
SRP is a public power utility not regulated by the Arizona Corporation Commission. They set their own rules and have chosen to implement demand charges and low export rates that disadvantage rooftop solar. Critics say it protects their business model; SRP says it ensures grid stability and fair cost allocation.
Can I avoid demand charges with SRP?
Not entirely, but a battery can significantly reduce them. By discharging the battery during peak usage moments, you can cut your demand peaks by 50-70%. Some customers also carefully manage appliance usage to minimize peaks.
Should I wait for better SRP policies?
Unlikely to improve significantly. SRP has shown no indication of becoming more solar-friendly. If anything, they may introduce more fees. Going solar now at least locks in current rates.
Is moving to APS territory an option?
If you're renting or planning to buy, checking the utility before signing could save you thousands over the life of a solar system. APS territory has meaningfully better solar economics.
What's the best battery for SRP customers?
You need a battery that can handle high discharge rates for peak shaving. Tesla Powerwall, Enphase IQ Battery, and Franklin aPower are all good options. Size for at least 10-13kWh to meaningfully impact demand charges.
Struggling with SRP Solar Math?
SRP is complicated. Our AI can help you understand demand charges, run scenarios, and determine if solar makes sense for your specific situation.
Ask About SRP Solar