Batteries vs No Batteries

Twelve-month bill comparison on a $49,649.5 annual baseline. Solar Only saves $24,386/yr; Solar + 87.3 kWh grid-tied battery saves $30,579/yr.

$49,650

Current annual SCE bill

$19,070/yr

New bill — Solar + Battery

$30,579

Annual utility savings

62%

% of current bill eliminated

What the battery adds on top of solar

$6,193.46/yr

Incremental savings beyond solar-only ($30,579 vs $24,386)

Solar alone clips midday energy charges but leaves the campus paying nearly the full demand charge — because the SCE peak window (4–9pm) falls after the sun goes down. The 87.3 kWh grid-tied battery captures midday surplus, then discharges into the 4–9pm window, cutting the demand component by roughly 22% on average and the energy component on the worst months by over 70%.

Real 12-month bill comparison

Monthly SCE bills — current vs solar + 87.3 kWh battery

Current billSolar + Battery

Source: engineering bill model (SCE TOU-GS-3 with PV/BESS dispatch). Each month's solar-only and solar+battery totals are calculated against that month's projected bill. Summer peak months (Jun–Sep) are where the battery's value compounds — those four months alone account for over $20,241 of annual savings with the battery.

Average day — 24-hour load profile

How the 87.3 kWh battery dispatches each day

Campus demandSolar productionBattery chargingBattery discharge (peak)

Grey line = actual campus demand (avg of 396 days). Yellow area = modeled solar production. Pink bars = battery discharge across the 4–9pm SCE peak window. Purple bars = battery charging from midday solar surplus.

Solar Only

No storage — surplus exports at NEM 3.0 rates

Current annual bill: $49,649.50
New annual bill: $25,263.61
Annual savings: $24,385.89
% of bill eliminated: 49%
Demand-charge exposure remaining: High — peak still hits after sundown

Solar + 87.3 kWh Battery

9 grid-tied modules — captures midday surplus, discharges at peak

Current annual bill: $49,649.50
New annual bill: $19,070.15
Annual savings: $30,579.35
% of bill eliminated: 62%
Incremental gain over solar-only: $6,193.46/yr

Month-by-month detail

Month	Current bill	Solar only	Solar + Battery	Battery's added savings
Jan	$2,439.30	$1,485.02	$1,255.99	$229.03
Feb	$2,255.12	$1,378.76	$1,244.21	$134.55
Mar	$3,432.79	$1,859.74	$1,531.53	$328.21
Apr	$2,464.21	$1,539.56	$1,274.36	$265.20
May	$2,582.68	$1,462.09	$1,231.09	$231.00
Jun	$6,713.62	$3,163.88	$2,166.66	$997.22
Jul	$7,087.94	$2,975.89	$1,599.60	$1,376.29
Aug	$8,261.49	$3,642.63	$2,631.31	$1,011.32
Sep	$7,072.16	$3,453.15	$2,496.43	$956.72
Oct	$2,382.68	$1,264.76	$1,045.68	$219.08
Nov	$2,453.07	$1,469.73	$1,182.69	$287.04
Dec	$2,504.44	$1,568.40	$1,410.60	$157.80
Total	$49,649.50	$25,263.61	$19,070.15	$6,193.46

Why this matters for the campus

The meter says peak demand happens exactly when the sun is gone

83 kWh

Avg daily consumption inside the 4–9pm SCE peak window

59 kW

Highest 15-min demand recorded; avg monthly peak 37 kW

120,807 kWh

Total measured over 396 days (111,349 kWh annualized)

Without storage, every kWh the campus uses between 4pm and 9pm is bought at peak rates (~$0.42/kWh), while the solar surplus from noon is sold back to SCE at ~$0.05/kWh under NEM 3.0 — an 8× value loss. The 87.3 kWh battery closes that gap by holding the midday surplus and releasing it across the peak window.

Bill modeling applied SCE TOU-GS-3 rates to the actual 15-minute interval data from meter 8001452485 (May 2025 – May 2026). Battery dispatch simulated against 87.3 kWh usable / 30 kW continuous discharge across the 9-module pack.