Solar Payback Calculator: System Size, Cost & Break-Even

Average monthly electricity use

kWh/mo

Average 12 months of bills — the kWh figure, not the dollar amount.

Electricity rate

$/ kWh

Total cost per kWh including delivery. The default is the EIA 2026 US residential average.

Sun region

Southwest — AZ, NM, NV, SoCal (~1,700 kWh/kW)Range 1,600–1,800 kWh/kWSoutheast / Texas (~1,450 kWh/kW)Range 1,350–1,550 kWh/kWMidwest / Northeast (~1,250 kWh/kW)Range 1,150–1,350 kWh/kWPacific Northwest (~1,100 kWh/kW)Range 1,000–1,200 kWh/kW

Sets annual production per kW installed. For your exact roof, run NREL PVWatts.

Share of use to cover

Many utilities credit exports above your own use at a low rate, so 80–100% is common.

Net system cost

Pays back in about 8.9 years · 7.4 kW system

System sizeAbout 10,800 kWh in year 1

PaybackCumulative savings ≥ net cost

Year-1 bill savingsAt $0.182 per kWh

25-year net savingsBill savings minus net cost

The federal Residential Clean Energy Credit (25D) is not available for systems placed in service after December 31, 2025. Leased and PPA systems follow different rules — check current terms with the installer.
Savings assume every kWh produced is worth your full retail rate (full net metering). Many utilities now credit exported power at a lower rate, which can stretch payback by years.

Key takeaways

Payback is sensitive to your electricity rate: at $0.218 (+20%) it is 7.5 years; at $0.146 (−20%) it is 10.8 years.
Every $0.25/W change in installed price moves the net cost by about $1,862.
After break-even, the system nets about $47,794 over 25 years at these assumptions.

System cost

7.45 kW system at $2.58/W$19,217

25-year net savings by sun region (production range)

Cumulative net position by year

Detailed numbers

25-year savings
Year	Production	Bill savings	Cumulative net
1	10,800 kWh	$1,966	-$17,251
2	10,746 kWh	$2,014	-$15,237
3	10,692 kWh	$2,065	-$13,172
4	10,639 kWh	$2,116	-$11,056
5	10,586 kWh	$2,168	-$8,888
6	10,533 kWh	$2,222	-$6,666
7	10,480 kWh	$2,277	-$4,388
8	10,428 kWh	$2,334	-$2,054
9	10,375 kWh	$2,392	$338
10	10,324 kWh	$2,452	$2,790
11	10,272 kWh	$2,512	$5,302
12	10,221 kWh	$2,575	$7,877
13	10,170 kWh	$2,639	$10,516
14	10,119 kWh	$2,704	$13,220
15	10,068 kWh	$2,772	$15,992
16	10,018 kWh	$2,841	$18,833
17	9,968 kWh	$2,911	$21,744
18	9,918 kWh	$2,983	$24,727
19	9,868 kWh	$3,058	$27,785
20	9,819 kWh	$3,134	$30,918
21	9,770 kWh	$3,211	$34,130
22	9,721 kWh	$3,291	$37,421
23	9,672 kWh	$3,373	$40,794
24	9,624 kWh	$3,457	$44,251
25	9,576 kWh	$3,543	$47,794

Cumulative net starts at minus the net system cost. The highlighted row is the payback year.

Show the math

900 kWh/mo × 12 = 10,800 kWh/yr
10,800 kWh × 100% ÷ 1,450 kWh per kW = 7.45 kW
7,448 W × $2.58/W = $19,217
− 0% incentives ($0) = $19,217 net cost
Year 1 savings = 10,800 kWh × $0.182 = $1,966; later years add 3%/yr in rates and lose 0.5%/yr in output
Payback ≈ 8.9 years (interpolated within the year cumulative net turns positive)

Solar Payback Calculator · BuildCalc

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Prices & assumptionsNational typical prices