Missouri gives you full retail netting every month, which is the arrangement most states have moved away from. It also does something few homeowners are told about: any credit you build up and do not use expires twelve months after it was issued, and you are paid nothing for it. That single clause decides how big your system should be, and getting it wrong is the most common way a Missouri array underperforms its quote.
Where a Missouri Kilowatt-Hour Ends Up
Under the Net Metering and Easy Connection Act at RSMo 386.890, with rules at 20 CSR 4240-20.065, every retail supplier in the state must offer net metering for systems up to 100 kW. Generation nets against consumption at full retail within the billing period. What happens after that is where the value falls away.
The verdict changes with the state line; see the state-by-state solar payback guide for how.
| What happens to the unit | What it is worth |
|---|---|
| Your house uses it inside the same billing month | Your supplier’s full retail rate; the statewide average is 12.36¢. |
| It becomes net excess and is credited to the next bill | The utility’s avoided fuel cost, a fraction of retail |
| That credit is still unused twelve months later | Nothing. It expires uncompensated. |
Read the three rows as a ladder you want to stay at the top of. Monthly netting is generous and does most of the work, because generation at noon offsets consumption that evening at full value. The problem only starts when a system produces more than the house consumes across a month, month after month, which is exactly what an oversized array does through a Missouri summer.
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Why the Expiry Punishes Oversizing Specifically
Missouri’s expiry rule is not one annual reset. Each credit carries its own twelve-month clock from the month it was issued, and a credit earned in June expires the following June whether or not you used credits from July. That is why the penalty falls on capacity you never use, month after month, rather than on a single date in the calendar.
A summer surplus does survive into winter, but at avoided fuel cost instead of retail, and anything still unused twelve months on expires. Size to monthly consumption, because netting resets each billing period; surplus beyond the month is repriced to avoided fuel cost and, if still unused, expires twelve months after issuance. A system built to fill a roof runs into that every year.
A typical Missouri installation is 8.59 kW at about $22,849, producing roughly 12,017 kWh a year against household use of around 1,001 kWh a month, which is a close match by design.
How much of the output the house uses | Annual value | Break-even |
|---|---|---|
House uses all of it, almost nothing spilling to credit | $1,443 | 15.8 years |
House uses most of it, some months in surplus | $1,401 | 16.3 years |
House uses well under it, regular surplus and expiring credits | $1,234 | 18.5 years |
Annual value and break-even use the 12.36¢ statewide average as a benchmark; rerun the chain with your supplier’s rate. These are EcoGen America’s own calculations from the Missouri figures in the EcoGen Solar Cost Index as of March 1, 2026. Ameren’s summer avoided fuel cost is reported near 5.39¢ and is treated here as indicative. Each supplier sets and restates its own figure as fuel prices move, so ask yours for the current value in writing. Evergy Missouri Metro and West apply the same twelve-month expiry under case EE-2019-0056. Simple payback before financing, rate rises and degradation.
Because most of the value sits in monthly netting at retail, that figure moves the break-even by well under three years across the whole range.
Cheap Power Is the Real Constraint
Missouri’s statewide average residential rate is 12.36¢, about 31% below the US average, and prices have risen about 2.99% a year. Ameren Missouri, Evergy Metro and Evergy Missouri West each file their own residential rate, and your netting runs on the one on your bill. Installations are reasonably priced at $2.66 per watt, and a kilowatt of panels here makes about 1,399 kWh a year.
That combination is why a state with full retail netting still lands in the mid-teens instead of under ten years. Netting decides what share of your output counts at full value; your rate decides what full value is worth. Missouri does well on the first and poorly on the second, and the second is the larger term.
There is no closing deadline and no successor tariff proceeding on the record in August 2026. Whatever else is true of Missouri, the arrangement is not scheduled to get worse.
When Missouri Solar Does Not Add Up
- If the quote is sized above what your house uses month to month. This is the Missouri-specific trap. Extra capacity produces credits that expire, so you pay for panels that eventually return nothing.
- If a proposal treats banked credits as savings. Ask directly what happens to a credit twelve months after it is issued. If the answer is not “it expires”, the model is wrong.
- If you are moving inside sixteen years. Simple payback runs 15.8 to 18.5 years on our figures, so time in the house is the deciding variable.
- If a projection assumes fast electricity price rises. Missouri has managed about 2.99% a year on a rate about 31% below the US average; a model built on more is assuming something the state has not done.
- If a quote shows a 30% federal credit. Section 25D is $0 for purchased systems whose installation is completed after December 31, 2025 under Public Law 119-21.
Missouri rewards restraint more than ambition. A system matched to what the house actually uses, on a roof you will keep for at least sixteen years, is a sound and unexciting investment; anything larger is buying credits that expire. Our Missouri incentives guide covers the rules in detail, and the Missouri installer list covers who works in the state.
Ask any installer to show monthly production against monthly usage before you sign.
Compare monthly production against monthly use
Missouri Solar FAQs
For a household on a supplier billing near the statewide rate, staying put, with a system matched to its consumption, yes, at a simple payback around 15.8 years on our figures, stretching to about 18.5 years for an oversized array. Missouri still offers full retail netting each month under RSMo 386.890, which is generous, but the statewide average residential rate is 12.36¢, about 31% below the US average, and cheap power limits what any system can return.
Yes, and this is the detail most quotes omit. Monthly net excess generation is credited to your next bill at the utility’s avoided fuel cost, and each credit expires uncompensated twelve months after it was issued. Each Missouri credit carries its own twelve-month clock rather than one shared annual reset date, so a credit earned in June expires the following June.
Size it to your monthly consumption, because netting resets each billing period. Surplus beyond the month is repriced to avoided fuel cost and, if still unused, expires twelve months after issuance, so capacity above what the house uses month to month returns very little. Ask any installer to show monthly production against monthly usage; if production runs above usage in most months, the system is too big for Missouri’s rules.
The utility’s avoided fuel cost, which is a fraction of retail. Ameren’s summer avoided fuel cost is reported near 5.39¢ and is treated here as indicative. Each supplier sets and restates its own figure as fuel prices move, so ask yours for the current value in writing. Evergy Missouri Metro and West apply the same twelve-month expiry under case EE-2019-0056.
There is no closing deadline and no successor tariff proceeding on the record in August 2026. The Net Metering and Easy Connection Act at RSMo 386.890 applies to all retail suppliers for systems up to 100 kW, and nothing on the record suggests it is scheduled to change.
References & Research Sources
EcoGen America reviewed RSMo 386.890, the Net Metering and Easy Connection Act, together with the rules at 20 CSR 4240-20.065, for the requirement that all retail suppliers offer net metering for systems up to 100 kW, for monthly one-to-one netting at full retail within the billing period, for the crediting of monthly net excess generation to the following bill at the utility’s avoided fuel cost, and for the expiry of those credits uncompensated twelve months after issuance; and Evergy Missouri Metro and West under case EE-2019-0056, which applies the same twelve-month expiry. A summer avoided fuel cost near 5.39¢ per kilowatt-hour is reported for Ameren’s Sheet 171 and is treated on this page as indicative. Each supplier sets and restates its own figure as fuel prices move. There is no closing deadline and no successor tariff proceeding on the record in August 2026. We also reviewed EIA Electric Power Monthly for the 12.36¢ residential price and the five-year growth rate of roughly 2.99% a year, and IRS guidance on the Public Law 119-21 termination of Section 25D. Output of 1,399 kWh per kilowatt per year, the 8.59 kW system size, the $22,849 installed cost, the $2.66 per watt figure and the 1,001 kWh monthly usage are EcoGen America figures, $2.66 per watt as of March 1, 2026. The payback figures are our own calculation and are simple payback before financing, rate escalation and degradation. Sources accessed between June 10 and August 18, 2026.
