Montana gives solar fair terms all year, then takes back unused credits on one date. With NorthWestern Energy, a typical owned system has a simple payback before incentives of about 12.8 years when the banked credits get used, and 15.0 years at Montana-Dakota Utilities. Lose half the bank at the yearly true-up and the wait grows by years: about nine in our earlier illustration. You pick that date.
Simple payback before incentives, NorthWesternAbout 12.8 years
Half the bank lost (our illustration)About 9 years longer
Typical owned 7.13 kW Montana system at $19,465 cash (EcoGen Solar Cost Index, September 2026), no incentives, NorthWestern’s EIA 12-month price less its $4.20 monthly customer charge (15.10¢), every banked credit used. No upkeep and no price rises are counted. The half-lost illustration uses our earlier basis: the 13.84¢ state average and $214 a year in owner costs. See the math.
- True-up date: pick the month before the form is filed.
- Utility: NorthWestern and MDU follow state law. Co-ops set their own rules.
- System size: match your yearly use. Extra kWh are given away.
2026 rules: new home systems get no 30% federal homeowner credit (IRS). Montana has no state solar rebate or tax credit. At NorthWestern and MDU, extra kWh still roll to your next bill 1 for 1, until the yearly reset.
How we checked this guide
Rules come from the Montana Code, NorthWestern Energy and the Montana DEQ; prices from the U.S. EIA. Assumed numbers are labelled.
The writer and checker shown above are EcoGen staff. EcoGen is paid when homeowners request quotes, which is explained beside the quote form. Read our editorial standards.
Five things that decide a Montana solar answer
Most of the Montana deal is good for the owner. Power you send to the grid comes back later as a kWh credit, one for one. The catch is the reset: once every 12 months, unused credits go to the utility unpaid. Read each row across.
True-up date
Worth a closer look
Your credit year ends in spring, after winter has used the summer bank.
Pause and check
The form says October, so the bank resets just before winter.
Check next: the settle-up month on your utility form.
System size
Worth a closer look
The system makes about what your home uses in a year.
Pause and check
The system is sized well past your yearly use. The extra kWh go to the utility unpaid.
Check next: your last 12 months of kWh next to the quote’s year-one output.
Utility
Worth a closer look
NorthWestern Energy or MDU bills you, so state law sets 1-for-1 credits up to 50 kW.
Pause and check
A co-op bills you and you have not seen its rules in writing.
Check next: the co-op’s credit value, reset date and any demand charge.
Roof and snow
Worth a closer look
A south-facing, unshaded roof steep enough to shed snow.
Pause and check
A shallow roof that holds snow all winter, or heavy shade.
Check next: a shade report and month-by-month winter output.
Price and time in home
Worth a closer look
A cash price near the Index’s $19,465 for 7.13 kW ($2.73 per watt), and you plan to stay past payback.
Pause and check
A dealer fee in the loan, or a likely move well before payback.
Check next: cash and financed prices side by side, with APR and fees.
One Montana system, two true-up outcomes
Simple payback is the years your savings take to cover what you paid: net cost divided by yearly savings. A kWh (kilowatt-hour) is the unit on your power bill. An export credit is what you get for each kWh your panels send to the grid. In Montana it is a kWh you can use later, so it is worth the full price if you use it before the reset.
- Cash price
- $19,465
- Confirmed incentives
- $0
- Year-one production
- 10,053 kWh
- Used at home / exported
- 40% / 60%
- Price for home use (EIA, 12 months, less the $4.20 customer charge)
- $0.1510/kWh
- Export credit (1 kWh for 1 kWh)
- $0.1510/kWh
- Upkeep counted
- $0/yr
- Used-at-home value
10,053 × 40% × $0.1510$607/yr - Export value
10,053 × 60% × $0.1510$911/yr - Yearly savings
$607 + $911$1,518/yr - Simple payback before incentives
$19,465 ÷ $1,518about 12.8 years
Inputs: the EcoGen Solar Cost Index typical Montana system (7.13 kW, $19,465 cash, September 2026) and our per-utility payback figures of October 19, 2026 (about 1,410 kWh per kW a year). NorthWestern’s EIA price for the 12 months to July 2026 is 15.71¢; taking out the $4.20 monthly customer charge leaves 15.10¢. A banked kWh used before the reset is worth the same as one used at once, so the 40/60 split does not change the result. No rebate is counted; Montana has none. These figures count no upkeep and no price rises. Montana-Dakota works out to 15.0 years and Flathead Electric to 24.1 years; the cost page shows the same 12.8 years for NorthWestern.
Now say the credit year ends on October 1, after a summer of banking and before the winter it was for. In the second case we assume half the banked kWh are lost: our assumption, not a measured Montana average. This illustration keeps our earlier basis, the 13.84¢ state average and $214 a year in owner costs, so its two figures compare with each other, not with the 12.8 years above.
| Scenario | Export credit | Export value | Yearly savings | Simple payback |
|---|---|---|---|---|
| Bank fully used | $0.1384/kWh | $834 | $1,176 | about 16.6 years |
| Half the bank lost | $0.0692/kWh | $417 | $759 | about 25.6 years |
In this illustration, about nine years of payback ride on one line of a form, and the slower case runs past the 25 years panels usually last. It is the cheapest fix in the whole purchase: ask which month goes on the form before it is filed.
Run your own Montana numbers
The tool starts with the bank fully used. Enter your own quote and bill, then press Calculate. To test a lost bank, lower the export credit. Nothing you enter is sent anywhere.
Example result
about 12.8 years
simple payback before incentives
- Used-at-home value
- $607/yr
- Export value
- $911/yr
- Owner costs
- $0/yr
- Yearly savings
- $1,518/yr
- Net cost
- $19,465
Starts with the bank fully used. Half the price as export credit means half the bank lost. Flat first-year values; rates, panel wear and repairs will change the result.
Why the reset month matters so much here
Montana panels make most of their power in summer; homes use the most in winter. So a system banks credits from spring to fall and spends them in winter.
The law lets you pick the day your credit year starts: January 1, April 1, July 1 or October 1. NorthWestern calls it the Annual Settle-up month. End the year in October and the summer bank is wiped just before you need it. End it in spring and winter has used the bank first. For most homes, April is safer.
Used at home: 4,021 kWh. Each one replaces power you would have bought, so it saves the full variable rate ($0.1510 here).
Sent to the grid: 6,032 kWh. These earn whatever your utility pays for exports ($0.1510 here). Here that matches the price you pay, but check your utility’s rule.
The 40/60 split is a planning assumption based on home-use research, not a measured Montana average. Use your own share in the calculator.
NorthWestern grants a once change of the settle-up month. Montana homes paid an average of 13.84¢ per kWh from August 2025 to July 2026 (EIA); NorthWestern cut its supply rate on October 1, 2026 and adjusts it next on January 1, 2027.
Find out which Montana utility serves you
NorthWestern, MDU or a co-op changes the rules. Ask each installer which one they modeled and which true-up date they will file.
Solar providers that serve your area may contact you, and they pay EcoGen for the introduction. How we make money.
Who bills you changes the rules
The state net metering law covers NorthWestern Energy and Montana-Dakota Utilities, which serve about 6 in 10 Montana homes. Rural electric co-ops set their own terms, so the example may not fit a co-op account.
| Utility | Share of Montana homes (EIA, 2024) | Net metering rules |
|---|---|---|
| NorthWestern Energy | about 59% | State law: 1-for-1 kWh credits up to 50 kW; reset month of your choice. |
| Montana-Dakota Utilities | about 3.5% | Rate 92, on the same terms as the state law. |
| Flathead Electric Cooperative | about 11% | Outside the state law. Ask for its terms in writing. |
| Yellowstone Valley Electric Cooperative | about 4% | Banks credits for 12 months; demand charges apply. |
Paying for it, and the tax break to claim
| Option | Who owns the panels | Upfront | Ongoing | Check before signing |
|---|---|---|---|---|
| Cash | You | Full price | None to a lender. | The true-up date on the form, and a size based on your use. |
| DEQ loan | You | Closing costs | A 3.5% fixed loan, up to $40,000 over 10 years. | Quarterly windows (October 1 to October 30, 2026 now); demand has beaten funds since April 2023. Do not finish before funding. |
| Bank or installer loan | You | Often $0 | Loan payment plus your utility bill. | Cash vs financed price. A dealer fee adds years. |
| Lease or PPA | Solar company | Often $0 | A monthly or per-kWh payment. | Whether one is offered here, and who sets the true-up date. |
DEQ’s example APR is 4.023% APR; the next window is January 1 to January 29, 2027. Property tax: up to $20,000 of a home system’s value is exempt for 10 years, so the typical $19,465 system falls under the cap. Send Form AB-14 to your Department of Revenue office by March 1. More in our solar financing guide.
Six lines a Montana quote should spell out
One line matters more than any panel brand: the true-up date on your utility form.
- True-up date in writing. The month the installer will enter on the utility form: January 1, April 1, July 1 or October 1.
- Utility name. Your utility and the rate the quote assumed.
- Size against your use. Year-one kWh next to a year of bills.
- Fees and meter timing. NorthWestern’s $200 application fee, and who waits for the net meter (up to 20 business days at homes without a smart meter).
- Property tax form. Who files Form AB-14 by March 1.
- Cash and financed prices. Both totals side by side, with any dealer fee shown.
Compare Montana solar quotes
Ask each installer for the true-up date they will file and a size based on your bills. Enter your ZIP code to request quotes from solar providers that serve your area.
How EcoGen is paid
EcoGen America does not sell or install solar. When you request quotes, we pass your request to solar providers serving your area, and they pay us for the introduction. Providers can include installers, solar marketplaces and lead exchanges, and more than one may contact you. You never pay us.
More Montana solar guides
- Montana solar guide: utilities, incentives and installers in one place
- Montana solar companies: compare local installers before you request quotes
- Montana solar incentives: bill credits, property tax and the DEQ loan
- What solar costs in Montana
- Free solar panels in Montana: what is real
- Are solar panels worth it? The national guide and payback calculator
All 51 state guides
Montana solar questions
Are solar panels worth it in Montana?
They can be for a home that stays put on NorthWestern or MDU. A typical owned system has a simple payback before incentives of about 12.8 years at NorthWestern and 15.0 years at MDU when all banked credits get used. Credits lost at the true-up add years, so your size and true-up date decide the rest.
What happens to unused Montana solar credits?
Extra kWh move to your next bill, 1 for 1. They keep rolling for 12 months. When that credit year ends, any kWh you have not used go to the utility with no payment, under Montana Code 69-8-603. Right-sizing and a spring reset keep that loss small.
Can I choose my Montana true-up date?
Yes. The law lets you pick January 1, April 1, July 1 or October 1 as the start of your 12-month credit year. At NorthWestern you choose the month on the application, and can change it once. For a home that uses most power in winter, April usually leaves the least to lose.
Is Montana net metering at risk?
It has been tested. On November 25, 2019, the Public Service Commission rejected NorthWestern’s net metering plan, including a demand charge estimated at $45 to $50 a month for new solar homes, and denied a new rate class. A 2017 law still lets the commission create one later, but only for systems connected after that decision.
Does Montana net metering cover electric co-ops?
No. The state net metering law does not apply to rural electric cooperatives, which serve many Montana homes. Each co-op sets its own rules. Yellowstone Valley Electric, for example, banks credits for 12 months and charges net metered accounts for demand. Get your co-op’s terms in writing.
Is there a Montana solar tax credit?
No. The state credit for home energy systems was repealed in 2021, and the federal homeowner credit ended for systems installed after December 31, 2025. What remains is a property tax break: up to $20,000 of system value is exempt for 10 years if you file Form AB-14 by March 1.
Sources, method and corrections
The example uses the EcoGen Solar Cost Index typical Montana system (September 2026) and our per-utility payback figures of October 19, 2026: NorthWestern’s EIA 12-month price with its fixed monthly charge taken out, no upkeep and no price rises. A banked kWh that gets used is valued at the full price. The second case is an illustration on our earlier basis: the 13.84¢ state average, owner costs of $30 per kW a year ($214 here, including a reserve for a new inverter), 40% of the solar power used at home as it is made, and half the banked kWh lost at the true-up. Those are our assumptions, not measured values. Simple payback uses flat first-year values. The calculator runs in your browser and sends nothing.
Spotted an error? Tell us through our corrections and feedback process.
- Montana Code 69-8-603: net metering credits and the yearly reset (checked September 30, 2026)
- NorthWestern Energy: net metering and private generation
- NorthWestern Energy: Level 1 interconnection request ($200 fee, one-time change to the settle-up month)
- Montana PSC: action on the NorthWestern rate case, November 25, 2019 (checked October 5, 2026)
- Montana Code 15-6-224: property tax exemption
- Montana DEQ: Alternative Energy Revolving Loan Program (checked October 1, 2026)
- Yellowstone Valley Electric Cooperative: net metering (a co-op example)
- U.S. EIA: average residential electricity price by state (12-month average, August 2025 to July 2026, as used in the Cost Index)
- IRS: Residential Clean Energy Credit (not available for property installed after December 31, 2025)
- EcoGen Solar Cost Index, September 2026: what solar costs in Montana
