CAISO 2026 Summer Assessment: 2,547 MW Surplus and 16 GW of Batteries

What CAISO projected for summer 2026

CAISO's 2026 Summer Assessment concludes the grid has sufficient energy for a wide range of conditions, with continued resource additions [caiso-2026-summer]. Key findings:

2,547 MW surplus above the industry standard for no more than one supply shortage event per ten years [caiso-2026-summer].

16,000+ MW of battery storage added since 2020, critical for hot summer evenings when solar drops [caiso-2026-summer].

6,194 MW of new capacity expected between April 1 and June 30, 2026, including 1,354 MW batteries, 1,370 MW solar, and 3,467 MW wind (including SunZia) [caiso-2026-summer].

Achieved planning reserve margin 30.8% in the tightest hour of the multi-hour stack analysis versus a 25% requirement derived from the probabilistic study [caiso-2026-summer].

Probabilistic modeling ran 500 full-year hourly scenarios [caiso-2026-summer]. Results address supply shortage events requiring emergency actions, not every wildfire or heat wave scenario.

Why surplus does not equal low cultivator bills

California cannabis facilities pay utility invoices, not CAISO LMP directly unless on specific indexed products. Bills combine:

Delivery (transmission, distribution, wildfire mitigation, public purpose programs).

Generation / supply (bundled utility, CCA, or Direct Access).

Demand charges on many agricultural and commercial schedules.

Fees and riders updated through GRC proceedings.

PG&E's 2027 General Rate Case seeks substantial delivery revenue increases through CPUC process [cpuc-pge-grc-2027]. CAISO surplus speaks to bulk reliability, not PG&E line replacement costs.

Batteries help the grid, not every grower equally

CAISO highlights batteries meeting the net peak after solar ramps down [caiso-2026-summer]. Cultivation peaks often occur on schedules (lights-on) that may align with evening grid peak in some facilities but not all.

A greenhouse in Salinas and an indoor room in Oakland have different overlap with system peak. On-site battery storage economics depend on your tariff's demand windows and whether NEM or VNEM applies.

System-wide 16 GW storage moderates energy price spikes. It does not remove demand charges on your utility bill.

Does your light schedule overlap CAISO net peak after solar ramps down?

CAISO identifies a multi-hour peak stack each summer day when load net of solar and wind is highest [caiso-2026-summer]. System batteries discharge into that net peak window, often between 6 p.m. and 9 p.m. in recent summers when rooftop solar fades [caiso-2026-summer]. Indoor cannabis peaks when lights energize, commonly mid-afternoon or early evening depending on harvest stagger.

Map three facility profiles against a simplified net-peak window (illustrative timing):

Profile	Lights-on window	Overlap with net peak	Demand charge risk
Single-flower flip 2 p.m.	2 p.m.–2 a.m.	Partial (HVAC carryover into evening)	Medium
Staggered three rooms, noon / 3 p.m. / 6 p.m.	Spread	High if 6 p.m. room aligns with net peak	High
Veg-only 6 a.m.–6 p.m.	Daytime	Lower evening overlap	Lower

A 750 kW peak facility on PG&E with a $18/kW-month demand charge (illustrative tariff input) pays $13,500 per month per billed kW. Shifting one 200 kW room flip from 6 p.m. to 10 p.m. may avoid setting billing demand during net peak even if kWh stays flat. CAISO's 2,547 MW surplus does not change that math [caiso-2026-summer].

Pull twelve months of interval data. Overlay CAISO peak hour publications. If your peak hour matches CAISO net peak more than 60% of summer months, prioritize scheduling before procurement. The ISO's 16,000+ MW of batteries help regional energy prices during the ramp [caiso-2026-summer]; they do not reset your utility demand window unless your tariff explicitly follows system peak.

Resource Adequacy vs CAISO surplus

Load Serving Entities must procure Resource Adequacy (RA) separately from CAISO's assessment [caiso-2026-summer]. RA costs appear on CCA and utility supply lines. A CAISO surplus means the ISO's probabilistic standard is met; your LSE may still charge RA compliance costs embedded in $/kWh.

Direct Access and CCA customers saw non-bypassable charge updates in 2026 procurement cycles. See California cultivation energy for DA lottery timing.

Risk factors CAISO still flags

Normal-condition surplus does not erase:

Extreme heat across the Western Interconnection raising AC load region-wide [caiso-2026-summer].

Wildfires taking transmission or generation offline [caiso-2026-summer].

Drought reducing hydro despite reservoirs at historical averages early in season [caiso-2026-summer].

Cannabis operators with backup power for crop protection should test fuel and transfer switches before August, independent of CAISO's base case.

Worked cost framing (illustrative)

Assume a 20,000 sq ft indoor facility in PG&E territory, 3.2 million kWh/year, 900 kW peak.

Cost layer	Driver	Notes
Energy (supply)	CAISO + RA + contract	May be flat via CCA
Delivery demand	Utility tariff kW	Lights-on sets peak
Wildfire mitigation	CPUC-approved rider	Grows with GRC
Efficiency compliance	Title 24, local rules	CapEx, not kWh

CAISO's 2,547 MW surplus might correlate with moderate energy prices on index products during normal weather. It does not cap delivery demand at 900 kW.

Procurement actions for 2026 summer

If on CCA, confirm RA and portfolio balance charges in the PCIA/NBC stack before comparing to DA.

If pursuing Direct Access, file six-month notice for the next lottery window per PG&E rules.

Schedule maintenance outside CAISO peak hours when possible to avoid setting billing demand during system stress.

Use interval data to check whether evening ramp overlaps your light schedule; shifting vege rooms may help demand windows.

Review California commercial rates for schedule changes independent of CAISO.

Long-term peak growth

CAISO forecasts peak demand rising from about 46,844 MW (2026) toward 52,940 MW by 2030 with 50% probability [caiso-2026-summer]. Data centers and electrification drive the upward track similar to PJM and ERCOT stories.

Cannabis is a smaller slice than data centers but adds steady baseload in agricultural zones. Local distribution upgrades can still trigger facility-specific demand charges even when ISO surplus is healthy.

Bottom line

CAISO's 2026 summer assessment is good news for grid reliability and likely moderates extreme wholesale energy scarcity under normal weather [caiso-2026-summer]. California cultivators should still budget delivery and RA lines separately. Surplus megawatts at the ISO do not pay your PG&E demand charge.

Resource Adequacy on your CCA or utility bill explained

CAISO's 2,547 MW planning surplus means the ISO's probabilistic standard is met for normal conditions [caiso-2026-summer]. Your load-serving entity still procures Resource Adequacy to serve retail customers [caiso-2026-summer]. RA costs show up as supply-side charges on bundled utility, CCA, or Direct Access bills, not as a line labeled "CAISO surplus."

Think of three layers:

Wholesale energy (LMP) moves hourly in the market.

RA compliance is a portfolio obligation your LSE must meet and embeds in retail rates [caiso-2026-summer].

Delivery is PG&E, SCE, or SDG&E wires and demand charges [cpuc-pge-grc-2027].

A Humboldt indoor grow on a CCA might see moderate energy prices during a normal CAISO summer while still paying rising delivery through PG&E's General Rate Case process [cpuc-pge-grc-2027]. CPUC public forums on PG&E's 2027 rate case highlight distribution and wildfire mitigation revenue needs separate from ISO energy conditions [cpuc-pge-grc-2027].

Illustrative annual stack for 900 kW peak, 3.0 million kWh, PG&E territory:

Layer	Illustrative driver	Notes
Energy	CAISO prices + contract	May ease with 16 GW batteries on system [caiso-2026-summer]
RA / portfolio	LSE compliance	Not eliminated by ISO surplus [caiso-2026-summer]
Delivery demand	Utility tariff kW	Lights-on schedule sets peak
Wildfire mitigation	GRC riders [cpuc-pge-grc-2027]	Rises independent of ISO surplus

CAISO expects 6,194 MW of new capacity between April 1 and June 30, 2026, including batteries and SunZia wind [caiso-2026-summer]. That additions pipeline supports reliability but does not bypass local transformer upgrades when you expand canopy. Facility-specific demand charges still apply even when the ISO reports 30.8% achieved planning reserve margin in the tightest hour [caiso-2026-summer].

Peak growth to 2030 and local distribution upgrades

CAISO forecasts peak demand rising from about 46,844 MW in 2026 toward 52,940 MW by 2030 at 50% probability [caiso-peak-growth-2030]. Data centers and electrification drive the upward track [caiso-peak-growth-2030]. Cannabis is a smaller slice, but new indoor rooms in agricultural counties still trigger local transformer requests through PG&E or SCE even when the ISO reports surplus [caiso-2026-summer].

Probabilistic modeling ran 500 full-year hourly scenarios addressing supply shortage events, not every wildfire or extreme heat outcome [caiso-2026-summer]. Cultivators should read CAISO surplus as normal weather reliability, not as immunity from August flex alerts or transmission derates [caiso-2026-summer]. Maintain backup power tests before harvest peaks regardless of ISO headline numbers [caiso-peak-growth-2030].

More than 16,000 MW of battery storage added since 2020 helps meet evening peaks when solar output drops [caiso-2026-summer]. System batteries moderate regional energy prices during the ramp; they do not reset your utility demand window unless your tariff follows system peak [caiso-2026-summer]. Pull interval data and overlay your light schedule against net peak hours before you assume surplus megawatts lower your bill [caiso-peak-growth-2030].