Solar panels in Knoxville, TN: payback and output
A kW of south-facing panels in Knoxville produces about 1,344 kWh a year, about the same as Nashville, the Tennessee reference city. Summer months produce 1.6× what winter does. To cover a typical 10,500 kWh/yr home on paper you'd need roughly 7.8 kW.
Output by month in Knoxville (kWh per kW)
Best: May · weakest: Jan.
Example 7 kW system in Knoxville
- Installed cost (example)
- $21,000
- Production, year 1
- 9,409 kWh
- Savings, year 1
- $1,290
- Payback
- 15.1 years
- 25-year net gain
- $17,751
Uses the Tennessee average price (13.71¢/kWh, EIA July 2026), full net metering and no incentives. Your utility's rate and export credit may differ — change them below.
Roof direction in Knoxville
Yearly output per kW of panels at a 20° pitch, and how it compares with a south-facing roof.
| Roof faces | kWh per kW/yr | vs. south |
|---|---|---|
| South | 1,344 | — |
| Southeast | 1,298 | −3% |
| Southwest | 1,285 | −4% |
| East | 1,172 | −13% |
| West | 1,154 | −14% |
| East-west (split) | 1,163 | −13% |
Calculate your home in Knoxville
Estimated payback
15.1 years
A slow payback: size, price and export credit matter a lot here.
≈ $107/month off your bill in year 1
- Year-1 savings
- $1,290
- 25-yr net gain
- $17,751
- Return (IRR)
- 4.9%
- Net cost
- $21,000
Cumulative savings minus cost
Production vs. use by month
9,409 kWh/yr
Covers 40% of your use directly; 45% of the output is used on the spot.
Which size pays off best?
Same usage and prices, only size changes. Best 25-year gain: 8 kW.
| Size | Cost | Year-1 savings | Payback | 25-yr gain |
|---|---|---|---|---|
| 3 kW | $9,000 | $553 | 16.5 years | $6,179 |
| 4 kW | $12,000 | $737 | 15.9 years | $9,072 |
| 5 kW | $15,000 | $921 | 15.5 years | $11,965 |
| 6 kW | $18,000 | $1,106 | 15.3 years | $14,858 |
| 7 kW | $21,000 | $1,290 | 15.1 years | $17,751 |
| 8 kW | $24,000 | $1,440 | 15.1 years | $20,541 |
| 10 kW | $30,000 | $1,440 | 17.8 years | $16,672 |
| 12 kW | $36,000 | $1,440 | 20.5 years | $10,672 |
Read the full Tennessee solar guide for net metering, orientation and price trends.
Other cities in Tennessee
Cities with similar sunshine
Solar in Knoxville: common questions
Are solar panels worth it in Knoxville, TN?
For an example 7 kW system costing $21,000 on a home using 10,500 kWh a year, payback in Knoxville is 15.1 years with full net metering and 20.0 years if exports earn half the retail rate, at the Tennessee average price of 13.71¢/kWh (EIA, July 2026).
How much electricity do solar panels produce in Knoxville?
About 1,344 kWh per year for each kW of south-facing panels at a 20° pitch (NLR PVWatts, typical-year weather), from 78 kWh in Jan to 135 kWh in May.
What size solar system does a home in Knoxville need?
About 7.8 kW to cover 10,500 kWh a year. Divide your own annual use by 1,344 kWh per kW for a first estimate; if exports earn less than retail, a smaller system often pays back faster.
Does roof direction matter in Knoxville?
Yes. Per kW at a 20° pitch: south 1,344 kWh, southeast 1,298 kWh, southwest 1,285 kWh, east 1,172 kWh, west 1,154 kWh, east-west (split) 1,163 kWh a year. South-facing roofs produce the most; east or west roofs still work, with less output.
Guides for going solar in Knoxville
- Payback · 4 minIs solar still worth it without the 30% federal tax credit?The 30% federal solar credit is gone for new systems. We ran payback for every state without it, and compared it with what the credit used to do.
- Planning · 3 minHow many solar panels do I need? Sizing from your electric billA step-by-step way to size a home solar system from your annual kWh, daytime use and local sunshine, with real size-vs-payback tables for four states.
- Payback · 4 minNet metering vs. net billing: how export credits change paybackHow much your utility pays for exported solar power can add years to payback. We compare full, half and quarter-retail credits in every state.
- Planning · 6 minEast- or West-Facing Roof: Is Solar Still Worth It?East- or west-facing solar panels made about 14.5% to 14.8% less power than south-facing ones across U.S. states. See where the loss is biggest and smallest.
- Planning · 6 minSolar Panels in Winter: Output by State vs. SummerHow much do solar panels make in winter? Winter vs. summer output per kW for U.S. states, why the gap grows up north, and what it means for net metering.
- Payback · 5 minRising electricity prices: where solar pays back fastestCompare electricity prices and solar payback by state: see where a rooftop system pays back fastest, where it is slowest, and why credit rules matter.
Data: NLR PVWatts v8 (U.S. DOE National Laboratory of the Rockies, formerly NREL), TMY weather near Knoxville (35.96, -83.92), 14% losses, retrieved 2026-10-11. Published 2026-10-15.