Switching Electricity Supplier With Solar in Massachusetts

By Olivier Beauchemin · Sourced from the Massachusetts DPU, the Attorney General's office, National Grid and Eversource, read October 9, 2026

Supply and delivery are two different purchases

A Massachusetts electric bill has two sections. In National Grid's 2025 Summary of Rates, the supply section is the cost of the electricity you use, which National Grid can buy on your behalf or you can buy from a competitive supplier. The delivery section pays for the wires, and the same document says it will remain the same even if you choose a competitive supplier. The DPU's shopping site, Energy Switch Massachusetts, labels supply as CHOICE and delivery as NO CHOICE.

National Grid's published R-1 delivery components add up to 22.829 cents per kWh plus a $10.00 monthly customer charge, and the Fixed Price Basic Service rate for August 2026 through January 2027 is 17.185 cents per kWh. For a household buying 600 kWh in a month, that is $146.97 of delivery against $103.11 of supply, so supply is about 41 percent of a $250 bill. A supplier offer is a bid on that 41 percent and nothing else.

Basic Service and its current price

Basic Service is the supply the utility buys for customers who have not picked a supplier. National Grid's Supply Costs page explains that its rates are based on the prices in its contracts with Basic Service suppliers, that the Fixed Price Option changes every February 1 and August 1 for residential customers, and that the Variable Price Option changes month to month. Its 2025 rate summary adds that National Grid does not mark up the price of power supply.

Figures are from National Grid's residential rate table and Eversource's electric supply rate pages, read October 9, 2026. Variable rates in both tables climb into winter. National Grid lists 18.477 cents for December 2026 and 20.086 cents for January 2027, and Eversource's Eastern Massachusetts table lists 21.054 and 25.510 cents for the same months. A supplier's fixed offer looks different against 15.6 cents in October than against 20.1 cents in January, so the comparison has to be made against the published rate for the months the contract covers.

The net metering credit when you have a competitive supplier

The credit is defined in the utility's net metering tariff. National Grid's Net Metering Provision, M.D.P.U. No. 1625, effective March 1, 2026, calculates the Standard Net Metering Credit for a residential solar facility each billing period as 100 percent of the excess kWh multiplied by the sum of four utility charges for the customer's rate class: the basic service charge in the customer's ISO-NE load zone, the distribution charge, the transmission charge and the transition charge. Eversource's net metering FAQ lists the same four components and says the energy efficiency, renewable energy, distributed solar and net metering recovery rates are excluded.

That tariff names the basic service charge, not "your supply rate", and the DPU spells out what it means for a customer who has switched. Its net metering eligibility page, under "Net metering and competitive supply", gives two billing cases.

• The supplier bills through the utility. Net metering credits apply to the entire bill, including the supply portion.
• The supplier bills you directly. Credits can only be applied to the non-supply charges on the utility's bill, such as delivery and taxes. The DPU's example is a customer who consumed 700 kWh in a month and must pay the supplier for all 700 kWh regardless of how much the solar facility generated.

In both cases, the page says, the value of the credit is based on the electric company's Basic Service rate and not the supply rate of the competitive supplier. So the supply component of a credit does not change when you switch. A switch changes the rate you pay for the kWh you buy, and the billing method decides whether the credit can touch the supply line at all.

The DPU's product overview says most competitive suppliers use the consolidated-bill option for residential customers, where the utility bills for delivery and supply and forwards the supply payment to the supplier. Under the dual-bill option you receive two monthly bills. For a solar owner the billing method is the first thing to read in an offer, because under a dual bill the panels' output never reaches the supply charge.

Eversource's FAQ adds one detail for a consolidated bill. A credit large enough pays off the distribution and supplier balances in full. A smaller one is split 50/50 between the two in Eastern Massachusetts for non-low-income customers, and applied to the supplier balance first in Western Massachusetts. National Grid's public pages do not describe an equivalent split, so a National Grid customer should ask the company how a partial credit is applied before signing.

What the Attorney General found

The Massachusetts Attorney General's office publishes an annual study comparing what residential competitive supply customers paid with what they would have paid on Basic Service. The report released March 31, 2026 found that over the last decade those customers collectively paid over $738.7 million more than they would have on Basic Service. For July 2024 through June 2025 alone, the net loss was $87.4 million, with low-income customers losing an average of $286 for the year and other customers $181. The same release reports that suppliers charging between 10 and 30 percent above the Basic Service rate account for more than 51 percent of customer losses.

Fixed, variable, and what happens at renewal

The DPU's product overview describes the two pricing structures suppliers sell. A fixed-price product has a price that remains constant for a specified period, from several months to several years, and may carry an early termination fee if you cancel before the end of the term. A variable-price product changes price, monthly in the overview's description, and the price is set either at the discretion of the competitive supplier or based on a specified market indicator. Most variable products have no specified contract term, so they can be cancelled without penalty.

Read the renewal clause for the rate that applies after the fixed term, whether the contract renews on its own, and how you are notified. The DPU licenses suppliers but, in its own words, does not oversee or regulate how they set their supply product prices. Only the contract tells you whether a fixed term rolls into a variable price at the supplier's discretion.

Auto-switch brokers, in their own words

Arbor is one service marketed to Massachusetts customers as a way to handle the shopping. This section reports what joinarbor.com says about itself, with no claim about results. It says it secures a better electric supply rate plan from trusted electricity suppliers, that the new rate will be on your utility bill in the next 1 to 2 billing cycles, and that you pay your same usual bill to your utility, but with a lower rate from an electricity supplier vetted by Arbor. On expiry it says it will alert you or secure a new one on your behalf, so you're not left on a variable rate. On money, it says that if you switch to a new supply rate through us, one of our energy supply partners gets a new customer and pays us a referral fee from their marketing budget, and that there are no cancellation fees.

For a solar owner the broker model adds nothing to the rule set above. The supplier it enrolls you with bills through the utility or directly, the credit is valued at Basic Service either way, and the offer is still a number to compare against the published rate for the same months.

Reading supply and delivery on a National Grid bill

National Grid's rate summary says you can determine whether National Grid is your supplier by looking at "Supply Services" on your electric bill. If that block names National Grid, you are on Basic Service. If it names another company, the rate printed on the line is that company's. The block shows the rate in dollars per kWh multiplied by the kWh billed, so the supply rate is on every bill.

The "Delivery Services" block lists the customer charge and the per-kWh components named on National Grid's rate page, with distribution and transmission the two largest. With solar, a month in which you exported more than you used shows the net metering credit as its own line, carried forward to the next bill.

To compare an offer, put the supply rate on the bill next to the Basic Service rate for the same months and the supplier's offered rate with its term and renewal clause. The difference between two published rates is the whole of what a switch can save on the supply line.

Why the supply rate matters to a solar owner

A solar system is sold with a production estimate, and many contracts carry a production guarantee that promises a number of kWh per year. When the system makes less than promised, the shortfall is counted in kWh and valued in dollars at the rate on your bill. A kWh the panels did not make is a kWh you bought at your supply rate plus delivery, or an export you did not earn a credit for, valued at the Basic Service component plus the delivery components.

Switching supplier changes the first of those. A 1,000 kWh annual shortfall valued at 17.185 cents of National Grid Basic Service supply is $171.85 on the supply line. At a supplier's 15 cents it is $150.00, and at 19 cents it is $190.00. Nothing about the shortfall moved. The rate did, and with it the amount a guarantee claim is about. The same arithmetic sits behind why an electric bill stays high after solar, where the usual cause is a gap between what the panels made and what the household expected.

OwlWatt's bill analysis reads an uploaded utility bill and records the supply line, the rate plan and the effective rate per kWh, so the dollar value of a shortfall is computed from the rate the household is paying in that period rather than from an average. Production is measured against a weather-adjusted expectation for the roof and tracked by contract year against the guaranteed figure. OwlWatt does not sell electricity and takes no referral fee from any supplier.

Outside Massachusetts

The credit rule on this page is the Massachusetts DPU's. Other states with retail choice value exported solar differently, and a utility inside a state can have its own tariff. Before switching with solar anywhere else, ask the utility in writing what rate values an exported kWh once a competitive supplier is on the account, and whether credits apply to the supply line at all.

Related Guides

• Why Your Electric Bill Is Still High After Installing Solar, and How to Verify It
• Solar Production Guarantees: What They Promise and How to Enforce One
• Solar in Massachusetts
• Solar Production Shortfall Claims