TL;DR: The Net Metering Expansion at a Glance
- What changed: The DPU raised the automatic cap-exempt threshold from 10 kW AC to 25 kW AC, effective February 2025.
- What "cap-exempt" means: Your system gets full retail rate net metering credits (~$0.36-$0.45/kWh) automatically, without waiting for cap space.
- 26-60 kW systems: Can also qualify if primarily serving on-site load and interconnection agreement dated January 1, 2021+.
- Who benefits most: Homes with heat pumps, EV owners, larger properties, and anyone pursuing whole-home electrification.
- Still pending: DPU 25-200 investigation could change credit values (not size eligibility). Install now to lock in current rates.
What Changed: The DPU Net Metering Expansion
In February 2025, the Massachusetts Department of Public Utilities (DPU) issued an order expanding the automatic cap-exempt eligibility threshold for net metering from 10 kW AC to 25 kW AC. This was one of the most significant regulatory changes for residential solar in Massachusetts since the SMART program launched in 2018.
Previously, any residential solar system larger than 10 kW AC required a net metering cap allocation from the utility. In many utility territories — particularly National Grid — the net metering caps were approaching their limits, creating delays and uncertainty for homeowners who needed larger systems. A homeowner with a heat pump and two EVs might need a 20 kW system, but could not get cap-exempt status for a system that large.
The DPU's order solved this problem. Now, any residential system up to 25 kW AC — which covers the vast majority of residential installations — automatically receives cap-exempt status and full retail rate net metering credits.
Before vs. After: Rule Comparison
The table below summarizes every major change in net metering eligibility rules following the February 2025 DPU order.
| Category | Before (Pre-Feb 2025) | After (Feb 2025+) | Impact |
|---|---|---|---|
| Cap-Exempt Size Limit | 10 kW AC | 25 kW AC | Systems up to 25 kW automatically receive full retail credits |
| Credit Rate (Cap-Exempt) | Full retail (~$0.36-$0.45/kWh) | Full retail (~$0.36-$0.45/kWh) | No change to credit rate — same 1:1 retail |
| Systems 11-25 kW | Required cap space allocation | Automatic cap-exempt eligibility | No more waiting for cap space to open |
| Systems 26-60 kW | Required cap space allocation | Cap-exempt if serving on-site load + interconnection dated Jan 1, 2021+ | Large residential/small commercial can qualify |
| Systems 61+ kW | Requires cap allocation | Still requires cap allocation | No change for large commercial systems |
| Carryover Credits | Roll month to month | Roll month to month | No change — excess credits carry forward |
What "Cap-Exempt" Actually Means for Your Bill
Understanding cap-exempt status is essential because it determines how much your exported solar energy is worth. Here is how it works:
Cap-Exempt (Full Retail)
- Credit rate: ~$0.36-$0.45/kWh (full retail)
- Eligibility: Systems up to 25 kW AC (automatic)
- No cap wait: Approved through interconnection process
- Example: 15 kW on Eversource earns $0.36 per exported kWh
- Annual value: $4,300-$13,500 depending on system size and utility
Cap-Allocated (Also Full Retail — When Available)
- Credit rate: Same full retail rate
- Eligibility: Systems over 25 kW AC (61+ kW)
- Cap wait: Must wait for cap space in utility territory
- Risk: Some territories approaching cap limits
- Delay: Can add weeks or months to project timeline
The critical point: cap-exempt and cap-allocated systems receive the same credit rate. The difference is only in how quickly and easily you get approved. Cap-exempt means no waiting, no uncertainty, and a faster path to interconnection. This is why the expansion to 25 kW is so significant — it removes the biggest bureaucratic barrier for larger residential systems.
Who Benefits Most from the 25 kW Expansion
The expansion was designed to address a growing problem: as Massachusetts pushes electrification through heat pump adoption and EV growth, residential electricity consumption is rising dramatically. Homes that electrify everything can see consumption double from 8,000-10,000 kWh/year to 18,000-25,000 kWh/year. The old 10 kW cap could not keep up.
Homes with Heat Pumps
Recommended: 15-20 kWAll-electric heating adds 4,000-8,000 kWh/year of electricity consumption. A 10 kW system often was not enough to offset the full load. Now you can install 15-20 kW to cover heating, cooling, and baseload.
EV Owners (1-2 Vehicles)
Recommended: 18-25 kWEach EV adds approximately 3,000-5,000 kWh/year. A two-EV household with a heat pump might need 20-25 kW to offset their full electricity consumption. Previously impossible under the 10 kW cap without cap allocation.
Larger Homes (3,000+ sq ft)
Recommended: 15-25 kWHomes over 3,000 square feet with central AC, pool pumps, and high baseload consumption often exceeded what a 10 kW system could offset. The 25 kW cap unlocks right-sized systems for these properties.
Whole-Home Electrification
Recommended: 20-25 kWHomes converting from gas/oil to heat pump HVAC, heat pump water heater, induction cooktop, and EV charging can see total consumption of 20,000-30,000 kWh/year. A 20-25 kW solar system makes full electrification pencil out.
System Size Scenarios: Annual Savings by Size
Here is what different system sizes produce and earn for Eversource and National Grid customers. All values assume ~1,200 kWh/kW annual production (typical for Massachusetts).
| System Size | Annual kWh | Panels | Eversource Savings | Nat Grid Savings |
|---|---|---|---|---|
| 10 kW (Old Cap) Average home, ~$200/mo electric bill | 12,000 | 24-26 panels | $4,308/yr | $4,680/yr |
| 15 kW (New Sweet Spot) Heat pump home + EV, ~$300-400/mo bill | 18,000 | 36-39 panels | $6,462/yr | $7,020/yr |
| 20 kW (Large Home) All-electric home, 2 EVs, ~$500+/mo bill | 24,000 | 48-52 panels | $8,616/yr | $9,360/yr |
| 25 kW (Max Cap-Exempt) Large property, pool, full electrification | 30,000 | 60-65 panels | $10,770/yr | $11,700/yr |
Savings include both self-consumed energy (avoiding purchase) and exported energy (net metering credits). Actual savings depend on your consumption profile and how much you self-consume vs. export. SMART 3.0 income ($0.03/kWh) adds an additional $360-$900/yr.
Utility-by-Utility Impact
Each Massachusetts IOU (investor-owned utility) has different rates and cap statuses. Here is how the 25 kW expansion affects customers by utility:
Eversource
$0.36/kWh10 kW Savings
$4,308/yr
15 kW Savings
$6,462/yr
25 kW Savings
$10,770/yr
Cap status: Open — cap space available in most zones
Largest MA utility. Most residential customers. Lowest of the three MA IOU rates.
National Grid
$0.39/kWh10 kW Savings
$4,680/yr
15 kW Savings
$7,020/yr
25 kW Savings
$11,700/yr
Cap status: Tight — some zones approaching cap limits
Large MA utility, mid-tier rate. Substantial benefit from bigger systems.
Unitil
$0.45/kWh10 kW Savings
$5,407/yr
15 kW Savings
$8,111/yr
25 kW Savings
$13,518/yr
Cap status: Open — smaller service territory, less congestion
Serves Fitchburg and surrounding area. Highest MA rate — largest savings per exported kWh.
Systems 26-60 kW: How to Qualify
The DPU order also created a path for systems between 26 kW and 60 kW AC to achieve cap-exempt status, though with additional requirements:
Eligibility Requirements (26-60 kW)
- 1Primarily serves on-site load: The solar system must be designed to primarily serve the electrical load at the property where it is installed. This is demonstrated by system sizing relative to historical consumption.
- 2Interconnection agreement dated January 1, 2021 or later: For new installations in 2026, this condition is automatically satisfied. It primarily affects systems that were installed under older interconnection agreements.
- 3Standard interconnection process: Submit your interconnection application to the utility as normal. The cap-exempt status is applied during the review process.
This 26-60 kW tier is most relevant for small commercial properties, large estates, multi-family buildings, and farms. Most residential customers will fall well within the 25 kW automatic cap-exempt threshold.
How This Interacts with DPU 25-200
It is important to understand that the 25 kW cap-exempt expansion and the DPU 25-200 net metering investigation are separate proceedings that affect different aspects of net metering:
25 kW Expansion (Resolved)
- What it addresses: System SIZE eligibility
- Status: Finalized and in effect
- Impact: More homes can install larger systems
DPU 25-200 (Pending)
- What it addresses: Credit VALUE ($/kWh)
- Status: Active investigation, decision expected late 2026-2027
- Impact: Could reduce credit rates for new installs
Why This Matters Right Now
Installing a larger system today takes advantage of both favorable conditions: the expanded 25 kW cap-exempt threshold and the current full retail credit rate. Systems interconnected before DPU 25-200 results in any changes are expected to be grandfathered at current rates. Waiting risks getting a larger system approved but at a lower credit value.
Frequently Asked Questions
What does "cap-exempt" mean for net metering in Massachusetts?
Cap-exempt means your solar system qualifies for full retail rate net metering credits automatically, without needing to be allocated space under your utility's net metering cap. Previously, only systems 10 kW AC or smaller were automatically cap-exempt. The February 2025 DPU ruling expanded this to 25 kW AC. Systems that are cap-exempt receive credits at the full retail electricity rate — approximately $0.36-$0.45/kWh depending on your utility.
When did the 25 kW cap-exempt expansion take effect?
The DPU order expanding cap-exempt eligibility from 10 kW to 25 kW AC was issued in February 2025. It applies to all new interconnection applications filed after the order date. Systems that were already interconnected at 10 kW or less continue under the prior rules (which were already favorable). If you submitted an interconnection application after February 2025 for a system up to 25 kW AC, you automatically qualify for cap-exempt status.
Can I install a system larger than 25 kW and still get net metering credits?
Yes, but with conditions. Systems between 26 kW and 60 kW AC can qualify for cap-exempt net metering if they primarily serve on-site electrical load and their interconnection agreement is dated January 1, 2021 or later. For new installations in 2026, this second condition is automatically met. Systems above 60 kW still require cap allocation. For most residential customers, 25 kW is more than enough to offset even fully electrified homes.
How does this interact with DPU 25-200 (the net metering investigation)?
DPU 25-200 is a separate proceeding investigating potential reductions to net metering credit values. The 25 kW cap-exempt expansion addresses system size eligibility, not credit rates. If DPU 25-200 results in reduced credit rates, it would affect the per-kWh value of credits but not the size eligibility. Importantly, systems interconnected before any rate changes are expected to be grandfathered at current rates. Installing a larger system now locks in full retail credits under both the size expansion and current rate structure.
Do I need a bigger electrical panel for a 15-25 kW system?
Possibly. A 15-25 kW solar system typically requires a 200-amp electrical panel. Homes with 100-amp or 150-amp panels may need an upgrade, which costs $2,000-$4,000. However, some modern inverters support "limited export" modes that allow larger solar arrays on smaller panels by limiting how much power is sent back to the grid. Your installer can assess whether a panel upgrade is needed during the site survey.
How many solar panels do I need for a 20-25 kW system?
A 20 kW system requires approximately 48-52 solar panels (using 385-415W panels), while a 25 kW system requires approximately 60-65 panels. This typically needs 1,000-1,600 square feet of unshaded roof space. Homes with limited roof area can use ground-mounted systems if they have sufficient yard space. Not every home has enough roof for a system this large, which is why a site assessment is the critical first step.
Will a larger system increase my property taxes?
No. Massachusetts law (M.G.L. Chapter 59, Section 5, Clause 45) exempts solar energy systems from property tax assessment for 20 years. This applies regardless of system size — a 25 kW system receives the same property tax exemption as a 10 kW system. The value added to your home by solar does not increase your property tax bill.
Is it worth installing a larger system now that the federal tax credit is gone?
For most homeowners with high electricity consumption, yes. Without the 25D federal tax credit, the primary financial driver of solar is displacing expensive grid electricity. A larger system displaces more electricity, which means more savings per year. On National Grid at $0.39/kWh, a 20 kW system saves approximately $9,360/year in electricity alone — compared to $4,680/year for a 10 kW system. The incremental cost of a larger system pays back through higher annual savings.
Ready to Right-Size Your Solar System?
With the 25 kW cap-exempt expansion, you can finally install a system sized for your actual energy needs — heat pump, EV, and all. Get a free site assessment and see what size system makes sense for your home.