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Four times a year, on the first of January, April, July and October, Montana law hands whatever solar credit you have banked to your utility and pays you nothing for it. That is not a penalty for doing something wrong. It is written into 69-8-603 as the ordinary annual true-up, on a date you designate. Everything else about Montana netting is generous, full retail one-to-one on systems up to 50 kW, but the calendar is the constraint that decides how big a system belongs on your roof and how you should use it.
One Date Resets Your Balance, and You Choose It
Within each month you net at your utility’s full retail rate, modeled here at the 13.2¢ statewide average, and a surplus carries forward as kilowatt-hour credits rather than as a devalued cash figure. That part is better than most states now offer. Then, once a year on whichever of January 1, April 1, July 1 or October 1 you have designated as the start of your 12-month billing period, any credits still unused from the previous 12 months are granted to the utility without compensation, under MCA 69-8-603(4).
Wondering whether Montana prices are high or low for the country? Our state-by-state solar pricing puts them in context.
If you designate | What sits in the bank on that date | Verdict for a heating-heavy home |
|---|---|---|
January 1 | Roughly half the summer surplus, still unspent ahead of the coldest months | Poor. Winter would have consumed those credits. |
April 1 | The year’s low point, drained by a winter of heating | The right pick for most Montana homes. Little left to surrender. |
July 1 | The spring build-up, just as peak production starts | Middling. The early-summer bank goes back to the utility. |
October 1 | The entire summer surplus | The costly pick. The bank is fullest right before winter needs it. |
The designation does real work. A heating-heavy home that picks October 1 surrenders its entire summer bank just before the season it was saved for; the same home on an April 1 designation surrenders almost nothing, because winter has already spent the credits. Same house, same panels, materially different value, decided by one box on the interconnection paperwork.
Enter your ZIP code and we will size a system to your true-up date rather than to a generic year.
Size a system around your true-up date
What Survived the 2019 Challenge
It is worth knowing how close this got to being worse. In December 2019 the Public Service Commission rejected NorthWestern Energy’s bid to end retail-rate net metering and place solar customers into a separate rate class. Retail netting survived, which is why Montana still offers a treatment that Nevada, Kentucky and others have moved away from. No closing deadline and no successor proceeding is currently on file.
Those terms are a policy position that can change. Montana statute covers NorthWestern Energy and Montana-Dakota Utilities. The electric cooperatives, and Flathead Electric serves about 13% of the state’s households, set their own terms entirely. If your power comes from a co-op, the 50 kW ceiling and the retail netting described here are not automatically yours and need confirming before you model anything.
Where Montana Costs Actually Land
At $2.81 per watt as of March 1, 2026, Montana sits mid-table, 23rd cheapest, a little under the national figure. Households here are modest users at 852 kWh a month, so the typical system is small: 7.25 kW at about $20,375 gross, producing roughly 10,223 kWh a year around Billings. That is among the lowest gross costs in the country, and it matters in a state where median home values run to $425,400 and roofs are frequently steep metal.
The benchmark across sizes, gross before incentives:
| System size | Gross at Montana’s $2.81/W benchmark |
|---|---|
| 5 kW | $14,050 |
| 6 kW | $16,860 |
| 7.25 kW, the typical Montana system | $20,375 |
| 8 kW | $22,480 |
| 10 kW | $28,100 |
Consumed as generated, that output is worth about $1,349 a year at the statewide average, a 15.1-year payback. Rate escalation has run 2.61% annually over five years, and the federal residential credit is $0 for systems you own whose installation is completed after December 31, 2025 under Public Law 119-21. There is no subsidy arriving to fix a poorly sized system, which puts the whole weight on getting the quarterly logic right.
That chain runs on the statewide average, which is ranking context rather than a billed rate. NorthWestern Energy files its own residential rate, so rerun the year and the payback with the rate on your own bill.
Where the True-Up Breaks the Case
- Anyone sold a system sized to annual usage. Annual is the wrong unit in a state that zeroes your balance four times a year. Ask for output and consumption by month, and look hard at May and June.
- Cabin and seasonal-property owners. A property occupied in winter and empty in summer is the worst possible match for a July 1 true-up.
- Cooperative customers who assume the statute covers them. It does not. Flathead, Yellowstone Valley and the others write their own rules.
- Anyone quoted well above $2.81 per watt. On a 7.25 kW system the numbers are small enough that a premium of 30¢ per watt is roughly $2,175 and adds well over a year to the payback.
Montana Solar Cost FAQs
About $2.81 per watt installed, 23rd cheapest in the country as of March 1, 2026. Montana households use relatively little power at 852 kWh a month, so the typical system is small at 7.25 kW, roughly $20,375 before incentives.
Yes, full retail one-to-one for systems up to 50 kW on NorthWestern Energy and Montana-Dakota Utilities, under MCA Title 69 chapter 8 part 6. Surplus carries forward as kilowatt-hour credits rather than a cash figure, which is better than most states now offer. Cooperatives are not covered and set their own terms.
At your annual true-up, on whichever of January 1, April 1, July 1 or October 1 you designate as the start of your 12-month billing period, when credits unused from the previous 12 months are granted to the utility without compensation under MCA 69-8-603. October 1 is the costliest designation for a heating-heavy home, because it surrenders the whole summer bank right before winter would have used it; April 1 is usually the right pick.
About 15.1 years for a household consuming what it generates, at 13.2¢ retail with rates rising 2.61% a year. Sizing matters more than usual: a system built to cover winter will bank credits through spring that a poorly chosen true-up date then removes, so a smaller, better-matched system often pays back faster than a larger one.
Nothing is currently pending. NorthWestern Energy asked the Public Service Commission to end retail-rate net metering and create a separate solar rate class, and the commission rejected that in December 2019. Retail netting survived and no successor proceeding or closing deadline is on file, though the history is a reminder that these terms are a policy decision.
The calendar decides this one. Enter your ZIP code and we will bring you installers who size against the true-up dates.
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Methodology: cost figures use the EcoGen Solar Cost Index for Montana, $2.81 per watt as of March 1, 2026, with payback modeled with no federal residential credit for owner-purchased systems, full retail netting with annual forfeiture on the designated true-up date, rate escalation at the state 5-year average of 2.61%, 0.5% annual panel degradation, and a 25-year horizon. Cooperative territories are excluded from the statutory terms described.
References & Research Sources
EcoGen America reviewed the Montana net metering statute directly, NorthWestern Energy program documentation, Public Service Commission order history, federal electricity price and utility datasets, Census home-value data, and federal tax guidance for this Montana solar cost guide. Sources were accessed between June 10 and August 18, 2026, unless another date is listed below.
- Montana Legislature. Montana Code Annotated 69-8-603. Net metering statute: monthly retail netting, kilowatt-hour carry-forward, and the annual surrender of unused credits on the customer-designated January 1, April 1, July 1, or October 1 start of the 12-month billing period. Statute read directly August 18, 2026.
- NorthWestern Energy. Home Solar and Net Metering Information. Utility net-metering documentation for Montana customers. Accessed June 11, 2026.
- Montana Public Service Commission (PSC). December 2019 Order on NorthWestern Solar Class Proposal. Rejection of the proposal to end retail net metering and create a separate solar class. Accessed June 11, 2026.
- U.S. Energy Information Administration (EIA). Electric Power Monthly, Table 5.6.A. Average residential electricity prices by state, March 2026 edition. Accessed June 10, 2026.
- U.S. Energy Information Administration (EIA). Form EIA-861: Annual Electric Power Industry Report, 2024. Residential customer counts for NorthWestern Energy, Flathead Electric, Yellowstone Valley Electric, and Montana-Dakota Utilities. Accessed June 10, 2026.
- U.S. Census Bureau. American Community Survey, 2024. Median home value data used for cost-to-value context. Accessed June 11, 2026.
- Internal Revenue Service (IRS). One, Big, Beautiful Bill Provisions. Guidance on Public Law 119-21, including termination of the Section 25D residential credit for systems whose installation is completed after December 31, 2025. Accessed August 15, 2026.
