Prologue · 1822 – 1920
Gas light
Boston's first energy plants stood on land made from the harbor, where coal arrived by ship.
The lens shows the 1867 fire-insurance atlas over today's aerial photo. Move it with your cursor. Drag the map to explore; use the slider to change the atlas year.
This is the North End gas works, the city's first energy plant. Its gasholder stood here from 1828 until the works moved to Commercial Point.
Sites and method from Genna Kane, "Making Power, Making Land" (Leventhal Map & Education Center, 2025).
Chapter 1 · 1886 – 1910s
Electric light
On 20 February 1886 the Edison Electric Illuminating Company of Boston lit its first customer, the Bijou Theatre, from one engine and two dynamos. Demand came in the evening, when the lights went on.
The state counted the new system the only way it knew how. Until about 1910 the regulator reported electric companies in lamps, not kilowatts.
Decision1885 & 1887 — the state creates a board to license gas, then electric, companies+
St. 1885 c. 314 created the Board of Gas Commissioners; St. 1887 c. 382 extended it to electric light and required a city's consent before a second company could string wires. Exclusive territory starts here.primary
Chapter 2 · 1889 – 1900
Streetcars
The streetcar system needed more power than any lighting company could sell it. So it built its own stations. This is the Central Power Station on Harrison Avenue, the largest in the city.
Look at the label on the 1902 atlas: Boston Elevated Railway Company (Lessee), printed over West End St. Railway Co. The biggest plant in Boston was rented.
Decisions1887 – 1897 — one company takes the streets, electrifies, and is leased to the Elevated+
1887. The General Court let the West End absorb Boston’s street railways, froze fares at their 1887 level and asked nothing for the use of the streets. The act →primary
1889. The Railroad Commissioners let the West End raise $4 million in new stock to electrify; shareholders, not riders, paid for the conversion. The order →primary
1894. The Boston Elevated Railway was chartered (St. 1894 c. 548, amended by St. 1897 c. 500). Whether either act let it generate its own power has not been found in the text. The charter →unverified
1897. The Commissioners refused a 99-year lease of the West End to the Elevated as “an unreasonable and excessive public burden”, then approved a shorter one; riders paid the fixed fare. The lease →primary
Chapter 2 · 1910
Streetcars made their own power
Boston was unusual. In 1910 its Edison company sold only 4.5% of its output to street railways. In Hyde Park the figure was 83%. Here, the traction company was its own utility.
Even a warehouse could do it. The Quincy Market Cold Storage company built a power house of its own at Sargent's Wharf.
Chapter 3 · 1921 – 1960
Appliances
Between 1910 and 1920, motors overtook lamps. The appliance era began on a grid that industry had already rebuilt around all-day load.
The rate schedule Boston Edison filed on 30 June 1921 priced household light flat, at 10 cents a kilowatt-hour plus 5 per cent, with no free wiring. Electricity used only for cooking, heating and refrigeration cost 2 cents above the first ten kilowatt-hours a month. The price depended on what the electricity was for.
Homes took to it slowly. In 1927 domestic service was 296.2 million kilowatt-hours, 14.7 per cent of what Massachusetts utilities sold.
Decision1921 — a rate you qualify for by owning an appliance+
Edison Electric Illuminating Co. of Boston, prices as filed on 30 June 1921 and reprinted by the Department of Public Utilities. Lighting: “for electricity for any use, 10 cents net a k.w.h. plus 5%” — flat, with a $9 minimum and “no free wiring”. Then the carve-out: “When energy is used only for cooking, heating and refrigeration … a rate of 2 cents a k.w.h. on all in excess of 10 k.w.h. a month.” Declining blocks did exist — 5¢, 3¢, 2½¢ — but only inside an optional yearly demand contract, and under “miscellaneous energy” at volumes no household of 1921 reached.primary
This corrects an earlier version of this page, which called the household tariff declining-block. It was not.
DPU Annual Report for the year ended 30 Nov 1921, Part II §1, pp. 47–49 →
The State decided who paid for the new load. In 1919 a new Department of Public Utilities replaced the gas-and-electric board, paid for by the companies out of customers’ bills. In 1920 a Newton householder asked the State to make Boston Edison wire his electric stove; the Department refused, because the cost would fall on “the small users”. And its accounting rules of 1921 gave every utility an account for wiring and appliances “furnished without charge to the consumer for the purpose of securing new business”, which all customers carried in rates.
The layer is still on the bill. Eversource again prices electricity by what it is used for: since the DPU’s 2025 heat-pump orders, a home that heats with a heat pump pays a lower winter rate, and every other residential customer makes up the difference.
Absence1923–1960 — the prices stop being printed+
The 1921 volume is the last to reprint what each company charged. The 1922 volume drops the “Prices” section; the bound 1926–1940 run carries no rate structure at all. The returns kept being filed — the Commission on Administration and Finance declined to authorise printing them. The silence in this chapter is a budget decision, not a lost archive, which is why the next four decades of this story are told with national data and photographs rather than Boston prices.primary
Chapter 4 · 1960 – today
Air conditioning
For most of the twentieth century, New England's biggest hour of demand came on a winter evening. Around 1990, a July afternoon overtook it — and stayed ahead.
The chart shows every year we could verify. The crossing was narrow: in 1993 the two seasons were 36 megawatts apart, two tenths of one percent. Boston got there earlier. By 1986 the city's summer peak was already 12% above its winter peak.
It arrived unevenly, and the unevenness is the point. In 1960 6.2% of homes in Boston’s suburban ring had air conditioning against 3.9% in the city. By 1980 the metropolitan figure was 42.7% and the city’s 30.5%. The ring was ahead at every census — and the ring is where the wires had the most room. Massachusetts also never ducted itself: central air reached 0.5% of homes in 1960 and 5.1% by 1980, so the cooling load arrived as window units, plugged in one at a time, on circuits nobody re-sized to receive them. Each pair compares places in the same census; the 1960 figures count occupied units and the 1980 figures year-round units, so read the ring-against-city gap rather than the climb between them.
Decision1985 — Boston Edison forecasts a switch back to winter peaking by 1995. It never came.+
The Energy Facilities Siting Council's 1987 decision on Boston Edison's long-range forecast records the company as "a summer peaking system" (1986: summer 2,519 MW, winter 2,246 MW) and notes its 1985 forecast of a switchover to winter by 1995. The region has been predicting its own return to winter peaking, and mis-dating it, for forty years.primary
Chapter 5 · 1960s – today
Gas heat
Heating went to gas. Under Boston runs a second grid: 1,513 miles of cast-iron main and 580 miles of bare steel — more leak-prone pipe than every other Massachusetts gas company combined.
The map shows reported gas leaks per square kilometer by census tract. Switch to see where pipe is being replaced.
Decision2014 — Chapter 149 creates the Gas System Enhancement Plan: replace the pipe, bill every customer+
St. 2014 c. 149 added G.L. c. 164 §145, letting gas companies recover the cost of replacing leak-prone pipe from all ratepayers through an annual plan. In 2024 the section was rewritten so the same money can retire pipe and build networked geothermal instead.primary
The wires · today
Transmission lines and substations
No power plant remains inside the city. Electricity arrives on high-voltage transmission lines — … of them at 345,000 volts, … at 115,000 — and steps down at … substations across Suffolk and Middlesex counties.
Thick lines are 345 kV, thin lines 115 kV. Dots are substations. Hover either.
The wires · today
The neighbourhood circuits
From each substation, feeders run beneath and along the streets at 13,800 volts — … circuits on this map — or on the older 4,000-volt network that still serves parts of the city, … circuits. A transformer on a pole or a pad drops each feeder to the 120 and 240 volts at your meter.
Everything in the rest of this story — the data center, the charger, the solar roof, the heat pump — plugs into one of these lines.
This is Eversource's own map of its distribution feeders. Hover any line for its circuit number, substation and voltage.
Decision1887 — one company per city: the consent rule that made the wires a monopoly+
St. 1887 c. 382 §3 required a city's consent before a second company could string wires in its streets. Exclusive territory begins here; today Eversource is Boston's only electric distributor.primary
The wires · today
Room for solar, and no figure for load
For every feeder, Eversource publishes how much new solar it could accept — its hosting capacity. … of … feeders have room for a megawatt or more; … have less than a tenth of that.
It publishes nothing about how much new load — chargers, heat pumps, computers — each feeder can take. That is the number the rest of this story keeps asking for.
Switch between voltage, room for solar, and the feeders that serve the downtown secondary network — the densest part of the grid, where the data centers sit. Then press Room for load. Same lines, same map, and the fourth one is blank: that figure is published for none of the … circuits.
Chapter 6 · from 1998
Data centres
In 1998 Boston Edison sold its power plants — 1,987 megawatts, Mystic and New Boston among them. Since then the big Boston-area plants have closed one by one. The last of Mystic shut in 2024.
The new customer ran flat, all day, every day. Massachusetts has … listed colocation buildings; … of them sit inside this map, and two are carrier hotels shared by more than one operator — 1 Summer Street, where Markley and DataBank both sit, and 70 Inner Belt Road in Somerville, shared by CoreSite and FirstLight.
They did not scatter. … of the facilities on this map sit nearest to feeders that Eversource’s circuit map lists under one bulk substation: Mystic — which carries the name of the generating station that closed in 2024. The plant left; the substation’s name stayed on the map of the load. (Nearest line by distance, not a service record: Eversource does not publish which circuit serves a building, circuits are switched between substations, and downtown buildings sit on a network fed from several at once.)
Blue lines are the feeders that serve the downtown network. Gold rings mark buildings with more than one operator. Hover a data center for its operators, its nearest feeder and the substation Eversource lists for it.
Decision1997 — restructuring: the utility sells its plants; large customers may buy power directly+
St. 1997 c. 164 (25 Nov 1997) opened retail choice and required divestiture. D.T.E. 97-113 (24 Apr 1998) approved the sale of Boston Edison's fossil fleet: Mystic 990 MW, New Boston 778 MW, Edgar, Framingham, West Medway, Wyman 4.primary
Chapter 6 · today
Data centres in the Boston market
Massachusetts has … listed colocation buildings in the Boston market, holding … separately operated facilities. … of the buildings are inside this map. They are not hyperscale campuses; they are floors and suites inside older commercial buildings, run by carriers and colocation landlords.
The map is 2023 aerial photography. Click any dot — or any building below — to fly in over its roof and read its operators, size, tier, certifications and feeder.
Chapter 6 · today
What data centres draw
Of the … buildings, … publish how much power they draw. Inside this map, exactly … does.
… publish a floor area, and most advertise their tier rating, their fibre carriers and their audit certifications in detail. Electricity — the thing that decides whether the feeder outside can carry them — is absent.
The four facilities in eastern Massachusetts that do publish a figure add up to … megawatts, and every one of them is outside Boston: Needham, Bedford, Northborough, Medford. (A fifth, the university consortium in Holyoke, publishes 10 MW and is across the state.) The downtown carrier hotel that anchors New England's fibre publishes its tenant count and its carrier count, and no megawatts at all.
Why it mattersA load nobody has to declare cannot be planned for+
Eversource publishes, per feeder, how much new generation it can accept. It publishes nothing about new load. Data centres publish floor area and certifications, not megawatts. Neither side of the connection is obliged to state the number that matters, so the public record cannot answer the simplest question about this map: if another one opens on that street, does the wire hold?primary
The one route to a real figure is the backup generators: diesel plant needs an air permit from MassDEP, and permits are public per site. That is the next thing to pull.lead
Chapter 6 · 2021 – 2026
Data centres in New England
As of 24 September 2026 no hyperscale data centre has been built or permitted in the six states. The map holds … live proposals, … stopped, … operating at scale, and … municipal bans, bylaws and moratoria, most of them voted in 2026.
The largest live figure is the … MW study at the retired Merrimack Station coal plant in Bow, New Hampshire — no developer named. Westfield's 2.7-million-square-foot campus, approved in 2021, has been dormant since 2022 and its company dissolved. Waterford's 300 MW at the Millstone nuclear station was denied; Millinocket's 60 MW at a paper mill is "considered dead"; Jay's operator walked seven weeks after the Governor vetoed a moratorium to protect it. The one operating AI-scale site, Markley's 50 MW in Lowell, added 27 diesel generators in 2025; a court paused four of them in August 2026, and the city voted a moratorium 10–0.
The towns chose thresholds an order of magnitude below the state's: Mansfield 2 MW, Everett 5 MW, Holyoke 12 MW — against Executive Order 658's 25 MW, ISO New England's 20 MW forecast floor and FERC's 50 MW. They are regulating the buildings Massachusetts already has, not the ones Virginia builds. Where projects were proposed, they went to the sites with wires already in the ground: a coal plant, three paper mills, a nuclear station, an air base.
The public forecast holds … GW of large load for the whole region. The utility's inbox holds …-plus hyperscale study requests at 1 to 5 GW. Texas's queue holds … GW against an all-time peak of …. The state that has no large loads has also built no rate instrument for them: no tariff, no docket, no rate class — an executive order, a paused tax exemption, and the towns.
Circle area is the megawatts named in the record; hollow circles published none. Blue is a live proposal, red is stopped, black is a town that has restricted the use, green is operating. Hover for the status, the vote and the source.
Decision2026 — the lease, the tariff, the allocation rule. Still not written.+
Who pays when a new load needs a bigger transformer? Eversource's Terms and Conditions (M.D.P.U. No. 3D) set a cost-sharing rule for single-family homes. For a large customer there is no written rule at all; the company decides "in the exercise of reasonable judgment."primary The DPU File Room returns no large-load docket; the 2024 climate law (St. 2024 c. 239) contains no occurrence of "data center" or "large load."primary
Executive Order 658 (8 Sep 2026): above 25 MW, no state permit without local consent and a community benefits agreement; developers must "directly procure or develop the energy resources to support their operations — without raising energy costs for ratepayers," or pay into a Ratepayer Protection Fund whose mechanism MassDEP must design by 31 December 2026.secondary
Terms and Conditions for Distribution Service → · ISO-NE 2026 large load forecast → · Lowell moratorium ordinance →
Chapter 7 · from 2011 – 12
Solar
Now the customer's equipment feeds the grid, or is paid to hold back. Boston has 4,466 solar installations, and a household battery enrolled in ConnectedSolutions is paid $275 per kilowatt each summer under the 2025–2027 plan (D.P.U. 24-149) to discharge when the grid asks.
Massachusetts records every installation by ZIP code, not by address. The largest concentration is ZIP …, with … systems.
Each circle is a ZIP code, sized by its number of installations. Hover for the split between houses, multifamily buildings and commercial roofs.
Chapter 7 · 2010s – 2020s
EV charging
By April 2023 Boston had … public charging stations with … Level-2 and … fast ports — … of them opened in 2021 alone. The city's own program adds … sites: … ports installed, … planned, … of the sites at the curb, and … curbside segments scored for the next round.
Blue dots are public chargers, sized by ports. Dark dots are the city's own sites. The tint is a ten-minute walk from an existing charger. Toggle the scored candidate segments.
Decision2022 & 2025 — ratepayers fund the charger's wiring; the host keeps the charger. Batteries are paid by the kilowatt.+
D.P.U. 21-90 (30 Dec 2022) approved $188 million of Eversource EV make-ready over four years — the utility pays the wiring up to the charger, recovered from all customers at 15 to 21 cents a month. D.P.U. 24-149 (28 Feb 2025) continued ConnectedSolutions; residential batteries under 50 kW earn $275/kW of average summer performance.primary
Chapter 7 · today
Chargers and the circuits
Each dot is a charger, coloured by its nearest feeder. … of the … public chargers are on feeders that also serve the downtown network; the rest spread across the territories of … substations. … sit on feeders with almost no published room for solar — which says nothing about room for a charger, because that number is not published.
| Bulk substation of the nearest feeder | Feeders | Chargers | Ports |
|---|
Each charger is matched to its nearest feeder from the map geometry — our computation, not the utility's. Hover a charger for its feeder and substation.
Chapter 8 · from 2019 – 22
Heat pumps
Heat pumps put winter heating on the electric grid. ISO New England expects the winter peak to overtake summer again around 2036.
The transformers sized for July in chapter 4 will be the wrong size. Massachusetts publishes no map of where the wires have room for new load; the utility's public map shows where solar can connect, not where heat can.
Behind the chart, the feeders are coloured by their published room for solar. Toggle the forecast between ISO New England's central and high cases.
Decision2023 — the gas utilities must plan to electrify. The wires plan to match is still being written.+
D.P.U. 20-80-B (6 Dec 2023) required gas companies to file decarbonization plans and, by 1 March 2026, proposals to retire pipe by targeted electrification.primary
Closing
No layer was taken away when the next arrived. The franchise, the pipes, the summer peak, the solar credits and the heat-pump rate are all still in the street and on the bill. The newest layer is being decided now.
Now, at your address
Every site in this story at once: the power plants and gas works of 1828–1930, today’s substations, and the data centres. Hover a dot for its name.
Look up an address on the map, and it answers five questions about the layers on your street:
- 1What am I paying for?
- 2Who owns it? Who do I call?
- 3Where does it come from?
- 4What is changing near me?
- 5What will it cost? Who decided?