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Analyze a commercial roofOne battery, three revenue lines. Enter your demand charge, your battery size and the peak you intend to shave, and see the whole stack — with every published rate labelled and every assumption stated.
Add three lines. Demand-charge savings: peak kW reduced × your demand rate × 12 months. Program revenue: the kW your battery can sustain through a dispatch event × the published rate — $200/kW in Massachusetts. Federal tax: a 30% Section 48E credit plus 100% first-year bonus depreciation. A 250 kW / 500 kWh battery on Eversource G-2 stacks $131,480 a year.
Demand-charge savings, demand-response revenue and federal tax treatment, from your own numbers.
Modelled on the Daily dispatch — National Grid Daily Dispatch and Eversource daily curtailment, both at the same rate.
Programme revenue is capped at the 250 kW this pair can hold up through a 2-hour dispatch — power alone does not qualify you.
How many kW you expect to shave off your billed peak. This depends on your load shape, not just battery size.
Distribution demand charge $20.21 + Transmission demand charge $13.74. Effective July 1, 2026. Source
The number that actually matters. Take it off your own bill or tariff — the presets are a starting point, not your rate.
No figure is assumed. Without your quoted cost the tax lines and payback stay blank rather than resting on a made-up price.
Recurring revenue
Annual demand-charge savings
$81,480
200 kW shaved × $33.95/kW-mo × 12
ConnectedSolutions revenue
$50,000
250 kW dispatch × $200/kW-yr
Stacked annual value, year one
$131,480
demand savings + programme revenue
10-year recurring value
$1,314,800
step-downs applied where the programme schedules them
Federal tax treatment
Section 48E credit (30%)
—
prevailing wage and apprenticeship required
First-year depreciation deduction
—
basis reduced by half the credit, 21% federal rate
Tax saved by that deduction
—
year one, undiscounted
Net cost after credit and depreciation
—
needs your installed cost
Simple payback
Enter a cost
Add your quoted installed cost above and this fills in. Nothing is assumed for you.
Demand-charge savings are an estimate. They assume you hold your billed peak down by the kW you entered in every billing month. Whether a battery achieves that depends on your load shape — how sharp your peaks are, how often they repeat, and whether they cluster at times the battery is also being dispatched. Utilities with a demand ratchet can also carry a bad month forward.
Both revenue lines are shown together. That assumes the battery can serve a programme dispatch and your own peak. In practice programme events are usually called in the same late-afternoon window as commercial peaks, so one discharge often does both — but a battery sized only for one will not deliver both.
Tariff presets. Eversource and National Grid do not build their demand charges the same way. Eversource bills a distribution demand charge and a transmission demand charge, both on your measured peak kW. National Grid bills a distribution demand charge only and recovers transmission through a per-kWh energy charge. The two $/kW figures therefore measure different things and cannot be compared directly, and a peak-shaving battery reaches a larger share of the bill on the Eversource structure for that structural reason rather than because power is simply dearer. Verified August 3, 2026against each utility's own published rate summary.
Federal treatment. Energy storage technology is not subject to the December 31, 2027 placed-in-service deadline or the July 4, 2026 begin-construction trigger — both apply to applicable wind and solar facilities only, and Section 48E(e)(4)(C) expressly excepts energy storage technology (IRS Notice 2025-42, section 2.02). A standalone commercial battery keeps the 30% Section 48E credit under the standard clean-electricity phase-out, which starts at the later of 2032 or when U.S. greenhouse gas emissions from electricity are 25% of 2022 emissions or lower. Bonus depreciation is applied at the current statutory first-year rate to the basis remaining after the credit. Confirm eligibility, prevailing wage and apprenticeship compliance, and your own tax position with a tax professional; tax-exempt entities take the credit as elective (direct) pay.
Modeled scenario disclosure
The profiles below are planning scenarios built from current market pricing, utility, incentive, and production assumptions. They are not verified NuWatt customer projects or guaranteed outcomes. A real proposal requires site, structural, utility, interconnection, financing, and tax-eligibility review.
A 250 kW / 500kWh battery at a Massachusetts facility on Eversource's G-2 medium general service rate, targeting a 200 kW reduction in billed peak. Every figure below is produced by the same calculation the tool above runs.
Battery A two-hour system, the common Northeast commercial configuration | 250 kW / 500 kWh |
Demand charge applied Eversource Eastern Massachusetts G-2, distribution plus transmission demand | $33.95/kW-month |
Peak reduction modelled A target, not a guarantee — achievable reduction depends on load shape | 200 kW |
Annual demand-charge savings 200 kW × $33.95 × 12 months | $81,480 |
Enrollable dispatch capacity What 500 kWh can hold up through a 2-hour event | 250 kW |
ConnectedSolutions revenue, year one 250 kW × $200/kW-year (Daily dispatch — National Grid Daily Dispatch and Eversource daily curtailment, both at the same rate) | $50,000 |
Stacked annual value, year one Demand-charge savings plus program revenue | $131,480 |
10-year recurring value Program rate schedule applied year by year | $1,314,800 |
There is no payback figure in that table, and that is deliberate
The scenario carries no installed cost, so it produces no Section 48E credit amount, no depreciation figure and no payback. NuWatt holds no primary-sourced commercial battery price to put there, and inventing one to complete the table would make every number below it wrong. Enter your own quoted cost in the calculator and those lines fill in from it.
Every preset in the calculator is a line item on a utility's own published rate summary, with the effective date printed on that document. Nothing here is derived from an aggregator, a news article, or an average.
| Preset | Components summed | Total per billing unit | Source & date |
|---|---|---|---|
Eversource (MA) G-1 Small General Service (Demand Price Option) Non-residential customers whose demand does not exceed an average of 100 kW over 12 consecutive months, who have elected the demand price option. | Distribution demand charge (above 10 kW) $22.31 + Transmission demand charge (above 10 kW) $19.34G-1 also offers a non-demand price option that carries no per-kW charge at all. A battery earns nothing against the non-demand option, so check which one the bill shows before modelling. | $41.65per kW-month | Eversource, 2026 Summary of Eastern Massachusetts Electric Rates for Greater Boston Service AreaEffective July 1, 2026 |
Eversource (MA) G-2 Medium General Service Service voltage under 14,000 volts with monthly demand above an average of 100 kW over 12 consecutive months. | Distribution demand charge $20.21 + Transmission demand charge $13.74 | $33.95per kW-month | Eversource, 2026 Summary of Eastern Massachusetts Electric Rates for Greater Boston Service AreaEffective July 1, 2026 |
Eversource (MA) G-3 Large General Service Service voltage of 14,000 volts or more, where the customer owns the protective devices and transformers. | Distribution demand charge $15.97 + Transmission demand charge $14.08G-3 also publishes an optional transmission coincident peak demand charge of $22.39 per kW, billed on the ISO coincident peak instead of the customer peak. That option rewards a different dispatch strategy and is not modelled here. | $30.05per kW-month | Eversource, 2026 Summary of Eastern Massachusetts Electric Rates for Greater Boston Service AreaEffective July 1, 2026 |
National Grid (MA) G-2 (Medium commercial and industrial) Massachusetts Electric commercial and industrial customers on the demand-billed medium general service rate. | Demand charge $15.06National Grid recovers transmission through a per-kWh charge on this rate class rather than a per-kW demand charge, so this figure is not the National Grid equivalent of an Eversource total. | $15.06per kW-month | National Grid, Massachusetts Electric Company Summary of Electric Delivery Service Rates, M.D.P.U. No. 1-26-CEffective February 1, 2026 |
National Grid (MA) G-3 (Large commercial and industrial, time of use) Massachusetts Electric large commercial and industrial customers billed on peak and off-peak usage. | Demand charge $10.48As with G-2, transmission is recovered volumetrically on this rate class. National Grid also publishes an optional transmission coincident peak demand charge of $23.82 per kW for customers who elect it. | $10.48per kW-month | National Grid, Massachusetts Electric Company Summary of Electric Delivery Service Rates, M.D.P.U. No. 1-26-CEffective February 1, 2026 |
Eversource Connecticut (CT) Rate 30 — Small General Electric Service Entire electrical requirements at a single service location through one metering installation, where the customer’s maximum demand is less than 200 kW. | Distribution demand charge (over 2 kW) $14.22 + Electric System Improvements demand charge (over 2 kW) $3.78 + Transmission demand charge (over 2 kW) $12.84 + Competitive Transition Assessment demand charge (over 2 kW) $1.47Every component is billed only on demand above 2 kW, so the first 2 kW of peak is never billed and a battery earns nothing against it. Connecticut delivery bills also carry Combined Public Benefits, Revenue Adjustment Mechanism and FMCC charges levied per kWh rather than per kW. They are outside this total because shaving peak demand does not reduce them. | $32.31per kW-month | Eversource, Summary of Connecticut Electric RatesLast updated May 1, 2026 |
Eversource Connecticut (CT) Rate 35 — Intermediate General Electric Service Entire electrical requirements at a single service location through one metering installation, where the customer’s maximum demand is less than 200 kW. | Distribution demand charge $8.69 + Electric System Improvements demand charge $2.22 + Transmission demand charge $14.58 + Competitive Transition Assessment demand charge $1.78Rate 35 covers the same 200 kW ceiling as Rate 30 but carries a $270 monthly customer service charge against Rate 30’s $44, trading a higher fixed charge for a much lower distribution demand rate. Which of the two a site is on changes what a battery saves, so read the rate code off the bill rather than inferring it from size. Connecticut delivery bills also carry Combined Public Benefits, Revenue Adjustment Mechanism and FMCC charges levied per kWh rather than per kW. They are outside this total because shaving peak demand does not reduce them. | $27.27per kW-month | Eversource, Summary of Connecticut Electric RatesLast updated May 1, 2026 |
Eversource Connecticut (CT) Rate 37 — Intermediate Time-Of-Day General Electric Service Entire electrical requirements at a single service location through one metering installation, where the customer’s maximum demand is less than 350 kW. | Distribution demand charge $8.69 + Electric System Improvements demand charge $2.22 + Transmission demand charge $7.29 + Competitive Transition Assessment demand charge $1.78A time-of-day rate. The demand charge is a single monthly charge on measured peak, but Rate 37 also bills transmission per kWh on-peak — weekdays noon to 8 p.m. Eastern Standard Time, 1 p.m. to 9 p.m. during Daylight Saving Time — at roughly four and a half times the off-peak rate. A battery on Rate 37 therefore earns from shifting energy out of that window as well as from shaving peak kW, and only the second of those is modelled here. Connecticut delivery bills also carry Combined Public Benefits, Revenue Adjustment Mechanism and FMCC charges levied per kWh rather than per kW. They are outside this total because shaving peak demand does not reduce them. | $19.98per kW-month | Eversource, Summary of Connecticut Electric RatesLast updated May 1, 2026 |
Eversource Connecticut (CT) Rate 56 — Intermediate Time-Of-Day Electric Service, Non-Manufacturers Non-manufacturing customers with an annual maximum demand of at least 350 kW but less than 1,000 kW, at a single service location through one metering installation. | Distribution demand charge $7.91 + Electric System Improvements demand charge $1.86 + Transmission demand charge $14.93 + Competitive Transition Assessment demand charge $1.85Billed per kVA, not per kW. kVA is apparent power, so a site with a poor power factor is billed against a larger number than its real-power peak, and a battery that removes one kW does not remove a full kVA. Read this total as dollars per kVA-month and check the power factor on the bill before converting it into a saving. Manufacturers at the same demand take Rate 55 instead, which is cheaper on every component. Connecticut delivery bills also carry Combined Public Benefits, Revenue Adjustment Mechanism and FMCC charges levied per kWh rather than per kW. They are outside this total because shaving peak demand does not reduce them. | $26.55per kVA-month | Eversource, Summary of Connecticut Electric RatesLast updated May 1, 2026 |
United Illuminating (CT) Rate GST — General Service Time-of-Use (demand metered) Optional for all requirements on a customer’s premises. A demand meter is installed, and the customer must remain on the demand rate, once consumption exceeds 1,560 kWh in a single monthly billing cycle. | Transmission $12.94 + Local delivery distribution $5.19 + New England Grid Operator cost $0.28 + Customer Produced Energy $0.59 + Miscellaneous and other mandates $0.19 + State Mandated Energy Purchases credit −$6.23Net of a $6.23/kW State Mandated Energy Purchases credit, which the tariff publishes as a negative line — adding United Illuminating’s per-kW charges without subtracting it overstates the demand charge by about half. The per-kW total is also a smaller share of this bill than an Eversource total is of its own: demand-metered Rate GST customers additionally pay 2.8662¢/kWh of distribution, so United Illuminating recovers much of delivery volumetrically and a battery that shaves kW reaches less of the bill than the $/kW alone suggests. Every component above is a peak-period charge; off-peak demand is billed at $0.00/kW and only on excess demand. A minimum bill of $8.71 per kW of peak demand in summer and $7.41 in winter also sets a floor that peak shaving cannot cut below. | $12.96per kW-month | The United Illuminating Company, General Service Time-of-Use Rate GST, C.P.U.C.A. No. 2508 (Docket No. 26-01-02)Effective July 1, 2026 |
These utilities are not comparable side by side
Eversource and National Grid do not build their demand charges the same way. Eversource bills a distribution demand charge and a transmission demand charge, both on your measured peak kW. National Grid bills a distribution demand charge only and recovers transmission through a per-kWh energy charge. The two $/kW figures therefore measure different things and cannot be compared directly, and a peak-shaving battery reaches a larger share of the bill on the Eversource structure for that structural reason rather than because power is simply dearer.
Connecticut’s two electric distribution companies do not build a demand charge the same way as each other, and neither builds it the way the Massachusetts utilities do. Eversource Connecticut states four separate delivery demand components — distribution, Electric System Improvements, transmission and the Competitive Transition Assessment — and bills its 350-to-1,000 kW classes per kVA of apparent power rather than per kW. United Illuminating states a shorter list of per-kW components and then subtracts a published State Mandated Energy Purchases credit, while recovering much of its distribution revenue through a per-kWh charge that no per-kW total can show. Read each row against its own bill, and never rank these totals against one another or against a Massachusetts total as though they were prices for the same thing.
Verified August 3, 2026. Massachusetts and Rhode Island program rates verified August 3, 2026; Connecticut program rates verified August 3, 2026.
Demand-charge savings are the cleanest arithmetic in the model and the most dependent on something the model cannot see: your load shape. One missed peak in a month costs that month's entire saving, and a utility with a ratchet clause can carry a bad month forward. Twelve months of interval data is what turns this estimate into a forecast.
Both revenue lines are shown together. In practice program events are usually called in the same late-afternoon window as commercial peaks, so a single discharge often does both jobs — but a battery sized for one will not deliver both, and any capacity you hold back as an outage reserve is capacity you cannot enrol.
Program payments follow measured performance across a season, not nameplate capacity. Enrolment caps apply — National Grid limits enrolled capacity to a multiple of site peak load, and Connecticut charges a commercial application fee and requires a minimum number of dispatches. The calculator models the published rate; it cannot model your acceptance into the program.
The credit and depreciation lines assume a taxable owner with liability to offset, at a 21% federal rate. Tax-exempt owners take the credit as elective (direct) pay and do not use depreciation at all. Confirm prevailing wage and apprenticeship compliance, and your own position, with a tax professional.
It adds three things up. Demand-charge savings are your peak-reduction target multiplied by the demand rate you enter and by twelve billing months. Demand-response revenue is the enrollable dispatch capacity — capped at what your entered energy can sustain for a 2-hour event — multiplied by the published program rate for your state. Federal treatment is the 30% Section 48E credit and 100% first-year bonus depreciation on the basis remaining after the credit. Payback appears only if you supply your own installed cost.
Send us twelve months of interval data and your current tariff and we will size against your actual peaks, not a target.