A 3,500 square foot home in Idaho typically uses about 1,691 kWh per month at the state average rate of 11.0¢/kWh (EIA). With 5.0 peak sun hours per day, most homeowners need a 13.6 kW solar system — roughly 34 panels at 400W. After the 30% federal ITC, net cost is about $28,500, with 14.7-year payback and $52,900+ in estimated 25-year savings.
Content roles: This page is your Idaho-specific sizing decision for 3,500 sq ft. For national methodology and roof/orientation depth, see the 3,500 sq ft national guide. For bill-based sizing, see $300/month (~$186/mo equivalent in Idaho). Policy depth: Idaho solar data.
⚡ System Size
How Many Solar Panels for a 3,500 sq ft House in Idaho?
Idaho electricity rates and sun hours change panel count versus the US average:
System size (kW) = Annual kWh ÷ (Peak sun hours × 365 × 0.82)
For 3,500 sq ft in Idaho:
Estimated monthly usage: ~1,691 kWh
Peak sun hours: 5.0 h/day
System size:13.6 kW (~34 × 400W panels)
Metric
Idaho
US average
Rate
11.0¢/kWh
16.3¢/kWh
Sun hours
5.0 h/day
4.5 h/day
System size
13.6 kW
15.1 kW
Panels (400W)
34
38
Idaho requires a smaller system than the national average for the same square footage. Use our solar system size calculator with your actual utility bills for a precise ZIP-level result.
Find your exact solar savings
Enter your ZIP code for a personalized estimate using your state's electricity rate and sun hours.
💰 System Cost
What Does Solar Cost for a 3,500 sq ft Home in Idaho After the ITC?
At $3.00/W installed (SEIA 2026), a 13.6 kW system in Idaho costs about $40,700 before incentives. The 30% ITC saves ~$12,210, for $28,500 net cost.
📈 Payback Period
How Long Is Solar Payback on a 3,500 sq ft Home in Idaho?
A 13.6 kW system saving ~$1,942/year pays back in about 14.7 years after the ITC. At 3% rate escalation, 25-year utility spend totals ~$81,400 vs $28,500 net solar — $52,900+ lifetime advantage.
Solar vs utility company · 25-year comparison
Total cost of staying on the grid vs owning solar for a $300/month bill (national average assumptions).
Idaho does not have a state solar tax credit. Idaho Power and Rocky Mountain Power offer net metering that credits homeowners at the avoided cost rate. The Idaho Energy Division provides educational resources, and some utilities offer renewable energy programs.
At Idaho's average rate of 11.0¢/kWh and 5.0 peak sun hours, a 3,500 sq ft home (~1,691 kWh/month) typically needs a 13.6 kW system — about 34 panels at 400W. See the [national 3,500 sq ft guide](/guides/how-many-solar-panels-3500-sq-ft-house/) for methodology.
A 13.6 kW system in Idaho costs roughly $40,700 installed before incentives. The 30% federal ITC reduces net cost to about $28,500. Idaho does not have a state solar tax credit. Idaho Power and Rocky Mountain Power offer net metering that credits homeowners at the avoided cost rate. The Idaho Energy Division provides educational resources, and som...
At $28,500 net cost and ~$1,942/year in bill savings, simple payback in Idaho is about 14.7 years.
Most Idaho homeowners in this size range see **$52,900+** estimated 25-year savings vs utility power. Equivalent monthly bill: **~$186** — compare the [$300/month bill guide](/guides/solar-panels-300-month-electric-bill/) for bill-based sizing.
The US average needs a 15.1 kW system at 11.0-year payback. Idaho needs 13.6 kW with 14.7-year payback at 11.0¢/kWh and 5.0 sun hours.
$300/month electric bill by state
System size and payback vary by electricity rate and sun hours — see your state.