Furnace Installation in Janesville, WI
A new furnace here will run from October through May every year. Tell us about the house, and a licensed contractor who covers Rock County will get in touch.
Tell us about the job
It takes about a minute.
Eight months of heat, and nights near 16 degrees
Janesville asks a lot of a furnace. Heat runs from October through May, eight months of the year, and winter nights average 16°F. A furnace here is not idling most of the year. It is working through more cold, more often, than in places with a shorter season.
Most homes in the area heat with gas, and any non-weatherized gas furnace built after November 2015 has to hit at least 80 percent AFUE by federal rule. That is the floor, not a target to aim for. Rock County has also logged 17 winter storms and 78 damaging wind events over the past ten years, the kind of weather that knocks out power along with the heat. Statewide, 18 percent of households went at least a day without power in 2024. A new furnace installed here should be sized and set up for that stretch of cold, not just the mild days in between.
- 8 months
- October through May, your furnace is on duty
- 16°F
- the average winter night it heats against
- 70%
- of homes here heat with gas, so most furnaces here burn gas
- 80% AFUE
- the federal minimum any new unit must meet
NOAA nClimDiv, 1991–2020 normals
A high-efficiency gas furnace would save about $90 a year to run in Rock County compared with a gas furnace.
Estimates for a typical Rock County home, from EIA household energy data, Wisconsin fuel prices and NOAA climate normals. Your home will differ.
Wisconsin requires contractors to register with the state.
That registration puts the business on file with the state, but nobody tests the contractor's work to get it. There is no trade exam behind the name, and Wisconsin does not let Rock County add its own HVAC license on top, so the registration is the only state record you get anywhere in the state.
For a furnace install, the protection that matters comes from the local building office instead. Most cities and counties require a permit for a furnace replacement and an inspection once the work is done, and that inspection is what checks the gas connection, since a bad one is the dangerous part of the job. Most homes in Rock County heat with gas, so that inspection is doing real work here.
Sources: Wisconsin Legislative Reference Bureau · Wisconsin Department of Safety and Professional Services
- What size furnace does my house need?
- It depends on the size of your house, how it's insulated, and how many windows it has, so there's no single number that fits every home. A contractor works this out with a heat load calculation, not by looking at the size of your old furnace. Getting this right matters here, since your furnace runs from October through May. Too big and it'll short cycle, too small and it won't keep up when it's 16 below outside.
- How do I know it's time to replace my furnace?
- Watch for rooms that won't warm up, a furnace that cycles on and off more than it used to, or repair bills that keep coming back. If yours is old and needs another repair, that's worth weighing against putting the money toward a new one instead. With heat needed here from October through May, a furnace that's struggling early in the season is only going to struggle more as it goes on.
- Is a high-efficiency furnace worth it?
- It depends on how long you plan to stay in the house and what furnace you have now. Since 2015, new non-weatherized gas furnaces have had to hit at least 80 percent AFUE, and high-efficiency models go higher than that, meaning less of the gas you pay for goes out the flue instead of into your house. With 70.2 percent of homes here heating with gas and winters running 16 below on average, that difference gets used a lot. A contractor can look at your current furnace and tell you what the jump in efficiency would actually mean for your house.