National Grid vs Eversource: How the Same State Ended Up With Rates 2x Apart

Look at a map of Massachusetts. National Grid serves the western and central parts of the state and pieces of greater Boston. Eversource covers most of the eastern half, plus the South Shore and Cape Cod. The two territories touch. People move between them. Many think the rates work the same way.

They don't.

Since 2015, National Grid's residential default supply rate — what the utility charges if you don't shop a competitive supplier — has climbed 103.2%. Over the same window, Eversource's default supply has fallen 58.6%. Per NREL's U.S. Utility Rate Database (URDB), which preserves every approved tariff revision filed with state regulators, that is the documented gap. Same Department of Public Utilities. Same wholesale ISO. Two opposite paths.

This post walks through how that happened, what the latest filed numbers show, and what it means for a household trying to figure out whether the default rate they're paying right now is normal or quietly broken.

Massachusetts default supply (called Basic Service) isn't a single annual number. It re-prices twice a year for residential customers, with summer and winter periods that the utility procures separately. URDB carries every approved revision since the system was rebuilt in the early 2010s.

For the most recent residential R-1 tariff revision on file:

A quick reality check on framing. The 25¢ National Grid number is a winter-period rate; summer rates fall back. The point is not that one specific bill cycle is double — the point is that the multi-year trajectory has separated wildly between two utilities that should look similar. Filed tariffs, not headlines.

Massachusetts doesn't have one statewide default supply auction. It has two. The DPU requires each utility to procure its own Basic Service on its own schedule, in its own territory.

That is the entire story.

A Basic Service auction is a sealed-bid request for blocks of wholesale power for a fixed period — six months for residential customers in Massachusetts. Suppliers bid, the utility picks the lowest offer per block, and the cleared price gets passed straight through to customers as that period's default rate. The utility itself doesn't mark it up. So whatever price the winning bidder hits, that becomes your default rate, plus delivery.

National Grid and Eversource ran into the auctions on different days, in different market conditions, for different load shapes. When wholesale natural gas spiked in late 2022 — Massachusetts is heavily exposed to constrained New England gas pipelines — the utility whose auction landed mid-spike caught a much higher cleared price. The one whose auction landed on a quieter week did not. Multiply that across six bi-annual auctions per utility, and trajectories diverge fast.

Nothing about this is illegal, hidden, or unusual. It is how state-procured default supply works. It just means “default rate” isn't a number — it's a procurement outcome that depends on a specific Tuesday.

Two things change once you understand the gap.

First, your “default rate” is not the same as a friend's “default rate” one town over. If you live in Worcester (National Grid) and your sister lives in Framingham (Eversource), you are paying for completely separate procurement events. Comparing your bills line by line and asking “why is mine higher” isn't pointless, but the answer is structural, not behavioral.

Second, shopping a competitive supplier is more attractive on the National Grid side than on the Eversource side, simply because the benchmark you're beating is higher. The Massachusetts Energy Switch site lists every certified supplier offer; the math is straightforward — find an offer beneath your current Basic Service price, check the contract length, check the early-termination fee.

The other piece worth understanding: switching doesn't move you off Eversource or National Grid. They still deliver electricity. They still fix outages. The only thing that changes is whose power they're delivering and what you pay per kilowatt-hour for it. The delivery half of the bill stays where it was.

Behind the supply-rate volatility, there's a piece of the bill that doesn't move with the auctions — the monthly customer charge. This is what you pay before the meter has registered a single kilowatt-hour.

Per the current Massachusetts tariff filings indexed in URDB:

That's about $120/year on each utility just for being a customer, before any electricity use. Compare that to Duke Energy Ohio at $3.95/mo (about $47/year) or PG&E in California at $0.00/mo, and Massachusetts is on the higher end nationally but symmetric between its two big utilities. The gap between National Grid and Eversource is on the energy-rate side, not the fixed-charge side.

Useful to know when you're reading a Massachusetts bill: about $10/mo is fixed no matter what, the rest scales with your usage and the current Basic Service rate.

Three steps:

1. Identify your utility. Look at the top of your most recent bill. It says “Eversource” or “National Grid.” If you're in the Berkshires or the Pioneer Valley, you're almost certainly National Grid. South Shore, Cape, and most of Boston are Eversource. There are pockets of overlap.

2. Find your current Basic Service rate. It's a line on your bill called “Basic Service” or “Supply.” Read it in cents per kWh. That's your benchmark for shopping.

3. Compare to certified supplier offers. The Commonwealth runs EnergySwitchMA.gov. Every offer there is from a supplier registered with the DPU. Sort by price. Filter for contract length you can live with. Watch for variable-rate plans that look low and then reset.

If the gap between your Basic Service rate and the lowest competitive offer is meaningful — and on National Grid territory right now, it usually is — switching is mostly paperwork. Your utility doesn't care which supplier signs your account. PG&E doesn't care which generator feeds the lines. Same wires, different invoice.

The National Grid vs Eversource split isn't a Massachusetts anomaly. It's what happens whenever “the default rate” in a deregulated state is actually a per-utility procurement instead of a per-state procurement.

Pennsylvania has the same dynamic, more extreme. Met-Ed's residential default has climbed 130% since 2015 while PPL Electric's has fallen nearly 60%. Same regulator (PUC), same PJM wholesale market, six utilities with six independent procurement calendars, six wildly different outcomes.

When news coverage says “Massachusetts electric rates are up X%” or “Pennsylvania electric rates went down Y%,” it's averaging across utilities that aren't doing the same thing. The state average is a useful headline number for context, but it doesn't tell you what bill your household is actually being handed.

The utility-specific URDB filings do. That's why we're building rate-history pages off them.