Mini Split Installation in Portsmouth, NH
A new system here will heat from October through May and cool from July through August 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.
A mini-split here works ten months a year
Winter nights average 18°F from December through February, and a mini-split has to pull heat out of that cold air for the full stretch from October through May. Then it switches over and cools through July and August, when afternoons average 80°F. Ten months of the year, one mode or the other is running.
Any mini-split sold today has to clear a federal floor either way, 7.5 HSPF2 for heating and 14.3 SEER2 for cooling. Given how many months yours will spend heating a cold house, it is worth knowing what the unit you install delivers above that floor, especially on the coldest nights.
- 8 months
- October through May, your system heats
- 2 months
- July through August, it cools
- 18°F
- the average winter night it heats against
- 80°F
- the average summer afternoon it cools against
NOAA nClimDiv, 1991–2020 normals
New Hampshire has no state license for HVAC contractors.
No state list of approved HVAC contractors exists here, and no state test a contractor in Rockingham County has to pass to do this work. Nothing is filed with New Hampshire that says who is qualified and who is not. The state leaves HVAC contractors alone entirely.
Most cities and towns in New Hampshire require a permit for an installation like this, with an inspection once the work is done. That inspection is a local building office checking the work. It is not a state license standing behind the contractor, because in Rockingham County there is no such license to stand behind it.
Source: New Hampshire General Court
- Is a mini split worth it?
- For most homes here it is worth looking at, especially if you're heating with fuel oil now. Fuel oil heats 42.2% of homes in this area, and a mini split moves heat instead of burning it, which cuts into that cost. Winters here get cold, down to 18°F on average overnight from December through February, so the unit has to be sized for that cold, not just for a mild day. A contractor can look at your house and tell you what size and how many units make sense.
- How many rooms can a mini split cover?
- A single outdoor unit can run anywhere from one indoor head to as many as eight, depending on the system. Each indoor head is sized to the room it serves, so a one-to-one setup heats and cools a single room well, while a multi-zone system spreads capacity across several rooms at once. The right number for your house depends on square footage, layout, and how the rooms are used, which a contractor needs to see in person to size correctly.
- Can a mini split heat a whole house?
- It can, if enough zones are installed and sized for the whole space, but that is a bigger job than a single unit in one room. Given how cold it gets here, down to 18°F on winter nights from December through February, a whole-house system has to be sized for that cold, not just for a mild day. A contractor can calculate the heat loss for your house and tell you what full coverage would take.