New Hampshire permit guide
Do you need a permit to replace a furnace, boiler or AC in New Hampshire?
Yes. Under RSA 155-A the state building code requires a permit to install, alter or replace the mechanical, gas and electrical systems it regulates, and your town issues it: the gas side needs a licensed fuel gas fitter, the wiring a licensed electrician. Here is which permit applies to which job, which code edition your town is enforcing, and what that means for an NHSaves rebate.
The rule that applies to every trade
New Hampshire has one building code for the whole state. Under RSA 155-A the State Building Code, the 2024 International Residential Code for one- and two-family homes and the 2023 National Electrical Code, each with New Hampshire amendments, applies in every city and town, and a permit is required before work covered by the code begins. What differs from town to town is the office that issues it: the state leaves permits, inspections and fees to each municipality, which is why each town page on this site starts with that town's building department.
Who applies is more open than in some states. The code lets the owner or the owner's authorized agent apply for a building permit, and New Hampshire issues no statewide general contractor licence. The trades are another matter: electrical installations need a licensed electrician, and gas fitting and plumbing need a licence from the Mechanical Licensing Board, in each case with a permit and inspection. The statute is explicit that the contractor is responsible for meeting the code, so the usual arrangement is that the contractor doing the work pulls the permit under their own licence.
Sources: RSA 155-A, New Hampshire Building Code (gc.nh.gov); NH Division of Fire Safety: State Building Code; International Residential Code 2024, Chapter 1 (ICC); OPLC: the licensing boards; RSA 319-C, Electricians (gc.nh.gov); RSA 153:27–36, plumbers and fuel gas fitters (gc.nh.gov).
Which code applies, and who issues the permit
The code is set at state level. The State Building Code Review Board recommends code updates and reviews the New Hampshire amendments, and the Division of Fire Safety publishes the adopted editions: from 1 July 2026, the 2024 International Residential Code and the 2018 International Energy Conservation Code, each with New Hampshire amendments, and the 2023 National Electrical Code. During the concurrence period to 31 December 2026 an application may follow either the 2021 or the 2024 codes, but not a mix of the two; from 1 January 2027 every application is under the new codes, and the edition in effect when the town receives the application governs the job to the end.
Enforcement is local, and it is the town's choice. RSA 155-A reserves permits, certificates of occupancy and fees to cities, towns, counties and village districts; a municipality that enforces the code adopts an ordinance, a building official who issues permits and inspects, a fee schedule, a building code board of appeals, that the Building Code Review Board must confirm, and local amendments may not be less stringent than the state code, may not touch its technical requirements and, since 1 July 2026, are limited to administrative matters. A few towns issue no building permit at all: Epsom has adopted no building codes and issues only a zoning permit, Wilmot has no building inspector, and Thornton issues a zoning compliance permit with no inspections. The state code applies in those towns all the same, and the contractor is responsible for meeting it.
The three towns have their own pages: Epsom, Wilmot and Thornton.
Sources: NH Division of Fire Safety: State Building Code; NH Division of Fire Safety: State Building Code Review Board; RSA 155-A, New Hampshire Building Code (gc.nh.gov); Town of Epsom: Zoning Compliance; Town of Wilmot: Planning Board; Town of Thornton: Zoning Compliance & Enforcement.
Heating and cooling in New Hampshire
Replacing a furnace, boiler or water heater, or installing a heat pump, ductless mini split or central air conditioner, is permitted work in New Hampshire: the code requires a permit to install, alter or replace any mechanical, gas or electrical system it regulates, and only portable appliances and minor part replacements are exempt. Anything on the gas side, a gas furnace, boiler, water heater or the piping to it, is fuel gas fitting, licensed by the state's Mechanical Licensing Board, and the wiring to a heat pump, mini split or condenser is an electrical installation that needs a licensed electrician. Ask your building department which permits it issues for the equipment itself; the contractor pulling them is expected to know.
New Hampshire has no separate HVAC contractor licence: the state's Mechanical Licensing Board licenses fuel gas fitters and plumbers, and oil heating technicians only on a voluntary basis, so do not expect an HVAC licence number. What you should expect is a fuel gas fitter licence on the gas work and an electrician's licence on the wiring, each with its own permit on file. The state also bars any town from restricting your choice of heating system or fuel supplier, so the decision between oil, propane, natural gas and a heat pump is yours.
If you are counting on an NHSaves rebate for a heat pump or central air conditioner, the conditions are the utility program's: a residential electric customer of Eversource, Liberty, Unitil or the New Hampshire Electric Co-op, equipment that meets the efficiency minimums, an install within the program year, and for the enhanced heat pump rebate a pre-verification before the install. A permitted, inspected installation is how the town documents the work; it does not replace the rebate paperwork.
The energy code is part of the permit too. Under the 2018 IECC with New Hampshire amendments, new heating, cooling and duct systems installed as part of an alteration must meet the code's residential mechanical provisions, with a narrow exception from duct testing for a short extension of an existing system. The New Hampshire amendments add a standard energy code form to the code, and the Division of Fire Safety posts a residential energy code application on its State Building Code page.
Sources: International Residential Code 2024, Chapter 1 (ICC); RSA 153:27–36, plumbers and fuel gas fitters (gc.nh.gov); OPLC: Mechanical Licensing Board; RSA 319-C, Electricians (gc.nh.gov); RSA 155-A, New Hampshire Building Code (gc.nh.gov); NHSaves: heat pump and central AC rebates; 2018 IECC with New Hampshire amendments, Chapter 5: existing buildings (ICC); NH Division of Fire Safety: State Building Code.
NHSaves rebates
The heat pump and central air conditioner rebates above are one side of NHSaves; the other is Home Energy Performance, the weatherization program of the same utilities. Its online Home Heating Index tool tells you whether your home qualifies for an energy audit, and a qualifying home gets incentives and low-interest financing for insulation, air sealing and other approved energy efficiency updates. Eligibility questions go to your utility, Eversource, Liberty, Unitil or the New Hampshire Electric Co-op, not to the building department.
Sources: NHSaves: heat pump and central AC rebates; NHSaves: energy audits and weatherization (Home Energy Performance).
Questions homeowners ask
Do I need a permit to replace my furnace, boiler or AC in your town?
Yes. The New Hampshire building code requires a permit to install, alter or replace a mechanical, gas or electrical system, and only portable appliances and minor part replacements are exempt. Gas equipment is fuel gas fitting, licensed by the state's Mechanical Licensing Board; the wiring to a heat pump or condenser needs a licensed electrician, and your town issues the permits. The contractor doing the work normally pulls them.
Do I need a permit to install a heat pump or mini split in New Hampshire?
Yes. The electrical connection is an electrical installation that needs a licensed electrician and an electrical permit from the town, and the equipment itself is mechanical work the code regulates. NHSaves rebates are the utility program's business, with their own equipment and paperwork conditions; they do not replace the permit.
How long is a building permit good for in New Hampshire?
Under the International Residential Code as adopted by New Hampshire (section R105.5), a permit becomes invalid if the work has not started within 180 days of issue, or if more than 180 days pass between inspections once work has begun; the building official may grant written extensions of up to 180 days at a time. An application that is filed but not pursued is treated as abandoned after 180 days.
Are building permits public record, and how do I look one up for an address in your town?
Yes, permits are public records. Ask the building department in your town how to search by address, or check the town's online portal if it has one.
Can a homeowner pull their own permit in New Hampshire?
Often, yes. The code lets the owner apply for the building permit, and New Hampshire's licensing statutes let the owner-occupant of a single-family home do their own electrical installations and, in an existing single-family primary residence, their own fuel gas fitting: still under a permit, to code and with the town's inspection. A licence is required for anyone else doing that work. Most homeowners still let the contractor pull the permit, because the statute makes the contractor responsible for meeting the code on the work they do.
What happens if work is done without a permit?
The town can order the work stopped, opened up for inspection, corrected or removed, and the code provides penalties for building or altering without a permit. Unpermitted work also surfaces at sale, when a buyer's attorney searches the permit history. It is far cheaper to permit it the first time.
Related New Hampshire permit guides
- Do you need a permit to replace windows in New Hampshire?
- Do you need a permit to replace a roof in New Hampshire?
- Do you need a permit to replace siding in New Hampshire?
Looking for your town's building department, permit portal and recent filings? Find it on the New Hampshire town pages.