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Get a Free QuoteModel peak shaving savings, CT ESS incentives ($250-$600/kWh), TOU arbitrage with Eversource CT and UI rates, and solar+battery stacking for commercial facilities. Demand charges of $8-$20/kW make battery storage a compelling investment.
Demand Charges
$8-$20/kW
Eversource CT & UI
ESS Incentive
$250-$600
Per kWh installed
TOU Spread
$0.08-$0.11
Peak vs off-peak /kWh
Grid Edge Bonus
$50-$100/kW
Annual dispatch revenue
A mid-size Connecticut warehouse on Eversource Rate 35 with 200 kW peak demand can save $12,000-$15,000/year by installing a 75 kW / 300 kWh battery system for peak shaving and TOU arbitrage. The CT ESS program provides $75,000 upfront ($250/kWh standard), and the system qualifies for the 30% federal ITC ($36,000 on net cost) plus MACRS depreciation. With Grid Edge dispatch payments adding $3,750-$7,500/year, total annual value reaches $15,000-$22,000 against a net cost of approximately $84,000 after all incentives — yielding a 4-6 year payback. Paired with a 200 kW solar array, the combined system saves $55,000-$65,000/year.
Connecticut commercial electric bills have two major components: energy charges (per kWh consumed) and demand charges (per kW of peak demand). Demand charges are based on your highest 15-minute average power draw during the billing period and can represent 30-50% of the total commercial electric bill. For facilities with spiky load profiles — manufacturing equipment startup, HVAC compressors, EV fleet charging — demand charges are disproportionately expensive relative to actual energy consumed.
Both Eversource CT and United Illuminating (UI) use demand-based rate structures for commercial and industrial customers. Eversource CT demand charges range from $10.47/kW to $18.65/kW depending on the rate class, while UI charges $8.25/kW to $16.50/kW. These charges apply to your single highest peak in the billing cycle — meaning one 15-minute spike on a hot August afternoon can cost hundreds of dollars for the entire month.
Battery energy storage systems (BESS) address this directly through peak shaving: the battery monitors facility load in real time and discharges during peak demand events, reducing the registered peak that determines demand charges. A well-sized battery can reduce peak demand by 20-40%, translating to $2,000-$15,000+ in annual demand charge savings depending on facility size and rate class.
Connecticut's electricity rates are among the highest in the nation, with commercial customers paying an average of $0.221/kWh and blended rates (including demand charges) of $0.27-$0.30/kWh. These high rates make the economics of battery storage particularly compelling in CT compared to most other states. The combination of high demand charges, wide TOU spreads, and generous state incentives creates a uniquely favorable environment for commercial battery investment.
Energy charges are billed per kWh consumed — like paying per gallon of water used. Demand charges are billed per kW of peak draw — like paying for the size of the pipe. A 200 kW peak facility pays $2,964/month in demand charges on Eversource Rate 35, regardless of total kWh consumed. Battery storage shrinks the pipe (peak) without reducing water flow (energy), directly lowering the demand component.
Connecticut has two investor-owned utilities serving commercial customers: Eversource CT (covering most of the state) and United Illuminating (serving the greater Bridgeport and New Haven areas). Each has distinct demand charge structures, TOU windows, and rate classes that affect battery storage ROI. Understanding your specific rate is the first step in sizing a battery system.
| Utility / Rate | Demand Charge | Peak Rate | Off-Peak Rate | TOU Spread |
|---|---|---|---|---|
Eversource CT Rate 30 (Small C&I) | $10.47/kW | $0.28/kWh | $0.18/kWh | $0.10/kWh |
Eversource CT Rate 35 (Medium C&I) | $14.82/kW | $0.26/kWh | $0.16/kWh | $0.10/kWh |
Eversource CT Rate 37 (Large C&I) | $18.65/kW | $0.24/kWh | $0.14/kWh | $0.10/kWh |
United Illuminating (UI) Rate GST (Small C&I) | $8.25/kW | $0.30/kWh | $0.19/kWh | $0.11/kWh |
United Illuminating (UI) Rate GT (Large C&I) | $16.50/kW | $0.27/kWh | $0.17/kWh | $0.10/kWh |
Peak Hours: Mon-Fri 12-8 PM (Jun-Sep), 7-11 AM & 5-8 PM (Oct-May)
Higher demand charges make battery ROI more attractive. Ratchet clause applies.
Peak Hours: Mon-Fri 12-8 PM (Jun-Sep), Variable (Oct-May)
Combined demand + TOU savings make battery storage highly cost-effective.
A key consideration: many Eversource CT commercial rates include a demand ratchet clause, which sets a minimum demand charge based on the highest peak from the prior 11 months. This means one summer spike can inflate demand charges for an entire year. Battery storage eliminates ratchet risk by preventing those peaks from ever being registered with the utility meter.
The Connecticut ESS program, authorized by PURA and administered through the CT Green Bank, provides the most generous battery storage incentives in New England. The program offers upfront capacity-based incentives that directly reduce installed cost, making commercial battery storage financially accessible even without solar pairing.
Critical timing note: The ESS program is transitioning from its current upfront incentive model to a performance-based model in April 2026. Under the new model, incentives will be paid over time based on actual grid services delivered rather than as upfront capacity payments. Projects that receive commitment letters before the transition date will be grandfathered under the current upfront structure. This makes Q1 2026 the optimal window to lock in the highest upfront incentives.
Eligible: All commercial customers in Eversource CT or UI territory
Max Size: Up to 1,000 kWh
Available for new standalone or solar-paired battery installations. Must be enrolled in dispatch program.
Eligible: Projects located in PURA-designated underserved areas
Max Size: Up to 1,000 kWh
Higher incentive recognizes grid reliability needs. Check PURA mapping tool for qualification.
Eligible: Affordable housing, community facilities in low-income census tracts
Max Size: Up to 1,000 kWh
Highest tier. Stacks with CT Green Bank financing and federal ITC bonus adders.
PURA has approved the transition of the CT ESS program from upfront incentives to a performance-based model starting April 2026. Under the new model, battery owners will earn payments based on actual dispatch events and grid services rather than receiving a lump sum at installation. Projects that secure commitment letters before the transition date are grandfathered at current upfront rates. For a 300 kWh system, this is the difference between $75,000 upfront versus performance payments spread over 10+ years. Act before April 2026 to maximize upfront value.
Peak shaving is the primary value driver for commercial battery storage in Connecticut. The battery continuously monitors facility load through a smart controller and automatically discharges when demand approaches the target peak threshold. This prevents the utility meter from registering a high demand reading, directly reducing the demand charge on the next bill.
The mechanics work in 15-minute intervals matching the utility metering window. When the controller detects facility load trending above the target setpoint (e.g., 140 kW on a 200 kW peak facility), it dispatches battery power to supplement grid supply, keeping the meter reading below 140 kW. The battery recharges during low-demand periods — overnight or during solar production hours — to prepare for the next peak event.
| Peak Reduction | Eversource Rate 30 | Eversource Rate 35 | Eversource Rate 37 | UI Rate GT |
|---|---|---|---|---|
| 25 kW | $3,141 | $4,446 | $5,595 | $4,950 |
| 50 kW | $6,282 | $8,892 | $11,190 | $9,900 |
| 75 kW | $9,423 | $13,338 | $16,785 | $14,850 |
| 100 kW | $12,564 | $17,784 | $22,380 | $19,800 |
| 150 kW | $18,846 | $26,676 | $33,570 | $29,700 |
Time-of-use (TOU) arbitrage is the second major revenue stream for commercial batteries in Connecticut. By charging the battery during low-cost off-peak hours and discharging during expensive peak hours, the battery earns the rate spread on every cycle. This strategy stacks on top of peak shaving — the same battery that reduces demand charges also captures TOU arbitrage value during its daily cycles.
Connecticut TOU windows are seasonal. Summer (June-September): peak hours are Monday-Friday 12-8 PM, coinciding with air conditioning load and ISO-NE system peaks. Winter (October-May): peak hours shift to morning (7-11 AM) and evening (5-8 PM), reflecting heating and lighting demand patterns. Battery controllers automatically adjust charge/discharge schedules to match the seasonal TOU windows.
Assumes 300 daily cycles/year, 90% round-trip efficiency, average $0.10/kWh peak/off-peak spread
100 kWh Battery
$2,700/yr
$225/mo
200 kWh Battery
$5,400/yr
$450/mo
300 kWh Battery
$8,100/yr
$675/mo
500 kWh Battery
$13,500/yr
$1,125/mo
The TOU spread varies by utility and rate class. Eversource CT commercial rates have a spread of $0.08-$0.10/kWh, while United Illuminating spreads are wider at $0.10-$0.11/kWh, making UI territory slightly more favorable for pure arbitrage strategies. However, Eversource CT's higher demand charges mean that the combined demand+TOU value is typically higher in Eversource territory for facilities with significant peak demand.
When paired with solar, TOU arbitrage becomes even more powerful. Solar production peaks during midday, and excess generation that cannot be used on-site can charge the battery for evening discharge during peak TOU hours. This effectively time-shifts solar production from mid-afternoon (when it may exceed facility load) to late afternoon and evening (when TOU rates are highest), capturing maximum value from every kilowatt-hour generated.
The combination of rooftop solar and battery storage creates a synergy that exceeds the sum of its parts. Solar reduces the energy charge component of the bill, the battery reduces the demand charge component, and together they provide TOU arbitrage and Grid Edge revenue. For Connecticut commercial facilities paying $0.27-$0.30/kWh in blended rates, the combined system addresses every cost driver on the electric bill.
Solar Energy Savings
200 kW x 1,175 kWh/kW x $0.221/kWh
Demand Charge Reduction
60 kW reduction x $14.82/kW x 12 months
TOU Arbitrage
300 kWh x $0.10 spread x 90% efficiency x 300 cycles
Grid Edge Dispatch
75 kW battery x $75/kW/year average
Total Annual Value
$76,330/yrThe combined incentive stack is equally compelling. The solar system qualifies for the 30% federal ITC (Section 48/48E), and the battery independently qualifies for the standalone ITC (introduced in the Inflation Reduction Act). The CT ESS incentive applies to the battery, while both components qualify for 5-year MACRS depreciation with 20% bonus in 2026. Connecticut's 6.35% sales tax exemption covers all equipment, and the 100% property tax exemption ensures the investment never increases your property tax assessment.
For facilities considering C-PACE financing through the CT Green Bank, the combined solar+battery system can be financed at 100% with no upfront cost. C-PACE terms of 20-25 years at 5-7% interest result in annual payments significantly below the combined savings, creating positive cash flow from Day 1. The business retains ownership and claims all tax benefits, while the CT Green Bank bears the financing risk.
Proper battery sizing requires interval data analysis, but these representative examples illustrate the economics at three common facility scales. All calculations assume Eversource CT Rate 35 ($14.82/kW demand charge), standard ESS incentive ($250/kWh), and 30% federal ITC on net cost after ESS rebate. Annual savings include demand charge reduction and TOU arbitrage. Grid Edge revenue is shown separately.
50 kW peak, 20 kW reduction target
200 kW peak, 60 kW reduction target
500 kW peak, 150 kW reduction target
The examples above show simple payback before MACRS depreciation. A C-corporation at the 28.5% combined rate (21% federal + 7.5% CT corporate) captures an additional 28.5% of the net depreciable basis in tax savings over 5 years. With 20% bonus depreciation in 2026, approximately 36% of the depreciable basis is deducted in Year 1 alone. Connecticut conforms to federal bonus depreciation, so these savings apply on both state and federal returns. For the mid-size warehouse example, MACRS adds approximately $22,000 in total tax savings, reducing effective payback by 1-2 years. See our CT IRR calculator for a full model including MACRS.
The Connecticut Grid Edge program provides a third revenue stream for commercial batteries beyond demand charge reduction and TOU arbitrage. Enrolled batteries receive dispatch signals during ISO-New England system peak events and earn performance payments for reducing grid load during critical periods. This program recognizes the grid reliability value of distributed battery storage and compensates owners for providing that service.
Grid Edge dispatch events typically occur 10-30 times per year, concentrated during summer heat waves and winter cold snaps when the New England grid is under stress. Each event lasts 1-4 hours, during which the battery discharges to reduce facility load on the grid. Payments are calculated based on the battery's enrolled capacity (kW) and actual performance during dispatched events.
25 kW Enrolled
$1,875/yr
$50-$100/kW range
50 kW Enrolled
$3,750/yr
$50-$100/kW range
75 kW Enrolled
$5,625/yr
$50-$100/kW range
200 kW Enrolled
$15,000/yr
$50-$100/kW range
Grid Edge participation does not conflict with demand charge management. The battery controller prioritizes facility peak shaving during normal operations and shifts to grid dispatch mode only during designated events. Since grid stress events often coincide with high facility demand (hot summer afternoons), the battery is already positioned to discharge — Grid Edge simply provides additional compensation for doing what the battery would already be doing for peak shaving.
A properly configured commercial battery in Connecticut generates revenue from three independent sources: (1) Demand charge reduction — $3,000-$38,000/year depending on facility size and rate class, (2) TOU arbitrage — $2,700-$13,500/year depending on battery size and cycling, (3) Grid Edge dispatch — $1,875-$15,000/year depending on enrolled capacity. Combined, these streams make commercial battery storage in CT among the most financially attractive in the country.
Complete guide to commercial solar in Connecticut: ITC, MACRS, C-PACE, net metering, and utility rate structures.
How C-PACE works in Connecticut: 100% financing for solar+battery, CT Green Bank, 140+ municipalities.
Full IRR/NPV calculator combining ITC, MACRS, net metering, demand savings, and CT tax exemptions.
Demand charges are billed based on your peak 15-minute power draw (in kW) during each billing cycle. In Connecticut, Eversource CT charges $10-$19/kW and United Illuminating charges $8-$17/kW depending on your rate class. These charges can represent 30-50% of a commercial electric bill. Battery storage reduces demand charges by discharging during peak usage moments, shaving the peak demand that determines the charge. Even a modest 20% reduction in peak demand can save thousands per month.
Our team will analyze your interval data, model peak shaving savings for your specific utility rate, and calculate the full incentive stack including CT ESS, ITC, and MACRS benefits.