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Janesville in short
- 29,330
- housing units in Janesville
- 30%
- built before 1960 (county 37.1%)
- 32.7%
- built 1960 to 1979 (county 27.7%)
- 1972
- median year built (county 1970)
The local numbers
How old the wiring is likely to be in Janesville
Of the 29,330 homes in Janesville, 4,173 date from 1939 or earlier, 14.2% of the total (Rock County: 19.2%). Knob-and-tube wiring was in common use from about 1880 into the 1940s, so those are the houses where it can still turn up behind plaster or in the attic. That is the lowest share of pre-1940 homes of the 5 cities on this site.
9,594 homes in Janesville (32.7%) were built from 1960 through 1979, more than the county's 27.7%. The CPSC says cable installed from 1965 to the mid 1970s may have aluminum branch wiring, so in that slice of the housing it is worth a look at the cable markings before adding outlets or a bigger panel (aluminum wiring). That is the highest share of 1960s and 1970s homes of the 5 cities on this site.
Janesville's median year built is 1972 (county 1970), and 30% went up before 1960. Many of the newer subdivisions already have 100- or 200-amp service, so the common jobs are added circuits, EV chargers and generators more than full service changes. That is the lowest share of pre-1960 homes of the 5 cities on this site.
Wiring eras: InterNACHI on knob-and-tube; U.S. CPSC on aluminum wiring.
Janesville housing and households vs Rock County
| Measure | Janesville | Rock County |
|---|---|---|
| Residents | 66,030 | 164,350 |
| Housing units | 29,330 | 71,109 |
| Occupied (households) | 28,326 | 67,201 |
| Owner-occupied households | 19,069 (67.3%) | 47,819 (71.2%) |
| Renter households | 9,257 (32.7%) | 19,382 (28.8%) |
| Single-family detached | 67.8% | 74.4% |
| Median year built | 1972 | 1970 |
| Built 1939 or earlier | 4,173 (14.2%) | 13,653 (19.2%) |
| Built before 1960 | 8,801 (30%) | 26,379 (37.1%) |
| Built 1960 to 1979 | 9,594 (32.7%) | 19,718 (27.7%) |
| Built 2000 or later | 15.2% | 16.3% |
| Mobile homes | 2.1% | 2.6% |
| In buildings of 5+ units | 15.5% | 11.7% |
Source: U.S. Census Bureau, ACS 2024 5-year (2020-2024), tables B01003, B25003, B25024, B25034 and B25035.
Local rules
Electrical permits and power in Janesville
- Permits and inspection
- The city's Building Division issues electrical permits and does the inspections. A permit is needed to upgrade an electrical service or to add new wiring or change existing wiring. If a licensed contractor does the work, the contractor pulls the permit and calls for every inspection, including the final. Wiring that will be covered up has to be inspected before it is covered. The Building Division is at (608) 755-3060. source
- What needs a permit
- Replacing an existing switch or outlet in the same spot does not need a permit. A homeowner who owns and lives in the house may pull a permit for branch-circuit wiring only. Anything on the service or the feeders of a single-family home needs a Wisconsin licensed Master Electrician, who pulls the permit. source
- Permit fees
- The city's published fee schedule (Municode Appendix A, read November 8, 2026) charges $51 for a residential service entrance or a generator, $51 for temporary service, $1.17 for each outlet, switch or light fixture, $16 for a feeder or subfeeder change, and $16 per central air or gas furnace unit. A new one- or two-family home up to 4,500 square feet is $163 per unit. source
- Power company
- Alliant Energy supplies power in Janesville. The city's electrical ordinance bars the power company from connecting service until the city's electrical inspector has issued a certificate of inspection, and Alliant says it sets a new or upgraded meter only after it receives the local inspection. source
The full fee table, who may pull which permit, and how inspections work are in Janesville electrical permits.
About Janesville. Janesville is the county seat of Rock County and sits on the Rock River; its 2020 census population was 65,615. Wikipedia
ZIP codes. 53546 (47% of its land), 53545 (28% of its land), 53548 (22% of its land), 53563 (4% of its land). Census 2020
Nearby, sharing a ZIP code with Janesville
Common questions
Janesville electrician questions
Who issues electrical permits in Janesville?
The city's Building Division issues electrical permits and does the inspections. A permit is needed to upgrade an electrical service or to add new wiring or change existing wiring. If a licensed contractor does the work, the contractor pulls the permit and calls for every inspection, including the final. Wiring that will be covered up has to be inspected before it is covered. The Building Division is at (608) 755-3060.
What electrical work needs a permit in Janesville?
Replacing an existing switch or outlet in the same spot does not need a permit. A homeowner who owns and lives in the house may pull a permit for branch-circuit wiring only. Anything on the service or the feeders of a single-family home needs a Wisconsin licensed Master Electrician, who pulls the permit.
How much is an electrical permit in Janesville?
The city's published fee schedule (Municode Appendix A, read November 8, 2026) charges $51 for a residential service entrance or a generator, $51 for temporary service, $1.17 for each outlet, switch or light fixture, $16 for a feeder or subfeeder change, and $16 per central air or gas furnace unit. A new one- or two-family home up to 4,500 square feet is $163 per unit.
Who supplies electricity in Janesville?
Alliant Energy supplies power in Janesville. The city's electrical ordinance bars the power company from connecting service until the city's electrical inspector has issued a certificate of inspection, and Alliant says it sets a new or upgraded meter only after it receives the local inspection.
How old are the houses in Janesville?
Per the ACS 2020-2024 5-year estimates, 4,173 of 29,330 housing units in Janesville were built in 1939 or earlier and 30% before 1960, against 37.1% for Rock County. The median year built is 1972.
What does a panel upgrade cost in Janesville?
No local electrician publishes prices, so the best guide is Wisconsin data: about $1,500 to $4,500 for a 200-amp upgrade, with older houses and aluminum wiring at the high end. Every range is on the cost page.
Electrical work coming up in Janesville?
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