Furnace Installation in Portsmouth, NH
A new furnace here will run from October through May every year. Tell us about the house, and a licensed contractor who covers Rockingham County will get in touch.
Tell us about the job
It takes about a minute.
Eight months of heat, and winters that test the install
Portsmouth needs heat from October through May, eight months of the year, with winter nights averaging 18°F. A furnace here is not idling most of the year and running hard for a few weeks. It is the system the house depends on for most of the year, and it has to hold up through nights well below freezing, one after another.
A lot of homes in this area still heat with fuel oil, and the equipment options and venting differ from a gas setup, so that is worth sorting out before installation, not after. Any non-weatherized gas furnace installed now has to reach at least 80.0 percent AFUE, that is the federal minimum. Power is also worth planning around. New Hampshire saw 22 percent of households lose power for 24 hours or more in 2024, and the region has logged 66 winter storms and 103 damaging wind events over the past ten years. A furnace that cannot restart on its own once power returns is a problem on the coldest night of the year.
- 8 months
- October through May, your furnace is on duty
- 18°F
- the average winter night it heats against
- 80% AFUE
- the federal minimum any new unit must meet
NOAA nClimDiv, 1991–2020 normals
New Hampshire has no state license for HVAC contractors.
There is no state list of HVAC contractors here and no exam behind the work. Whatever confidence you have in the person doing this job has to come from somewhere other than a license, because in this state there is not one.
For a furnace installation, the protection comes from the local building office. In most cities and towns, replacing a furnace needs a permit, and the finished work gets inspected once it is done. That permit and inspection are what stand in for a license here.
Source: New Hampshire General Court
- What size furnace does my house need?
- It depends on your house, and a contractor will size it with a heat loss calculation rather than a guess. That calculation looks at your square footage, your insulation, your windows, and your ceiling height, because two houses the same size can lose heat at very different rates. Going by square footage alone leads to a furnace that is too big or too small, and either way you end up paying for it in comfort or in wear on the unit. With winter lows around 18°F here, getting the size right matters more than in a milder climate.
- How do I know it's time to replace my furnace?
- The clearest sign is a furnace that can't keep up or one that needs repair every year. If yours is running constantly without warming the house, cycling on and off in short bursts, or the burner flame looks yellow instead of blue, those point to a unit that's failing rather than one that just needs a fix. Age matters too. A furnace installed before November 2015 is running below the 80 percent AFUE efficiency that's now the minimum, so an older unit is burning more fuel to make the same heat. With heat needed here from October through May, a furnace that struggles isn't a minor inconvenience, it's most of the year.
- Is a high-efficiency furnace worth it?
- For a house that needs heat eight months a year, a high-efficiency furnace makes more sense here than in a place with a short winter. Nearly all new gas furnaces have to hit at least 80 percent AFUE, but high-efficiency models go well beyond that, meaning less fuel burned for the same heat over a long heating season. Fuel oil heats 42.2% of homes here, and if that's your setup, ask a contractor how efficiency ratings compare across oil and gas equipment, since the numbers aren't measured the same way. A contractor can walk through the actual models and what each one would mean for your house.