No plug-in solar legislation had been introduced in Montana as of our last check. That doesn't make every plug-in setup illegal, but there is no law that exempts small systems from your utility's interconnection rules — so connecting one without permission may violate your service agreement.
Off-grid use is a different story: a portable panel charging a battery power station that is not connected to your home wiring needs no permission anywhere.
What plug-in solar is worth in Montana
Montana households pay an average of 14.99¢ per kWh, 18% below the US average of 18.31¢. With roughly 4.6 peak sun hours a day, here is what a well-placed system produces and saves. We assume panels facing south at about 30°, 86% system efficiency and 80% of output used on-site.
800 W kit (2 panels)
- Saved per year
- $139
- Payback ($900 kit)
- 6.5 yr
- Energy used
- 924 kWh/yr
- 25-year net
- $2,563
1,200 W kit (max)
- Saved per year
- $208
- Payback ($1,300 kit)
- 6.3 yr
- Energy used
- 1,386 kWh/yr
- 25-year net
- $3,895
Run your own numbers
Change the orientation, mounting and size to match your balcony.
Estimated savings · Montana
$139/ year
≈ $11.54 per month
- Payback
- 6.5 yrs
- Energy used
- 924 kWh/yr
- 25-year net
- $2,563
- CO₂ avoided
- 749 lb/yr
Monthly savings profile
Estimates only. Rate: EIA July 2026 state average; sun hours: long-term averages. See our methodology.
What to do now
- 1Don't connect a grid-tied plug-in system yet — without a law, it may breach your utility agreement.
- 2Consider an off-grid setup in the meantime: a panel charging a portable power station is legal everywhere.
- 3Cut your bill today with no-cost measures — see our guide to lowering your electric bill.
- 4Contact your Montana state legislators: constituent support is what moved the 2026 bills.
Montana plug-in solar FAQ
Is plug-in solar legal in Montana?
Not yet. No plug-in solar legislation has been introduced so far. Without a law, connecting a grid-tied plug-in system may violate your utility's interconnection rules. Off-grid setups (a panel charging a portable power station) are allowed everywhere.
How much can balcony solar save in Montana?
At Montana's average residential rate of 14.99¢/kWh (EIA, July 2026) and about 4.6 peak sun hours a day, a south-facing, tilted 800 W kit saves roughly $139 a year, paying back a $900 kit in about 6.5 years. Vertical railing mounts produce about 30% less.
What is the maximum plug-in solar size in Montana?
There is no Montana-specific cap yet. Most state laws settle on 1,200 W, the practical limit for a standard 15-amp, 120 V circuit.
Sources
- Exact Solar — state-by-state plug-in solar update (Jul 2026)
- EIA — Electric Power Monthly, Table 5.6.A (residential prices)
Not legal advice. Laws and effective dates can change; confirm with official Montana sources and your utility.