Best HVAC Contractors in Nassau County, NY (2026)

Best for: Nassau homeowners who want Manual-J-sized installs, a public pricebook, and premium-tier equipment (Trane, Mitsubishi Hyper-Heat, Bosch IDS, Rheem).

• Headquartered in Nassau — local dispatch, not an out-of-county call center
• Manual J / D / S done in-house on every install proposal
• PSEG-LI Home Comfort Participating Contractor — files heat-pump rebates at install
• 1-year labor / 10-year parts warranty standard; Synchrony financing

Best for: Mitsubishi ductless / Hyper-Heat retrofits and ducted high-efficiency conversions in central Nassau.

• Mitsubishi Diamond Elite installer (extended compressor warranty)
• Strong ducted + ductless expertise across Nassau
• Solid established review base in Garden City, Mineola, Manhasset

Best for: Multi-trade Nassau jobs where one company handles HVAC + plumbing + electrical on the same visit.

• Wide Nassau footprint with large fleet
• 24/7 dispatch and same-day availability
• Plumbing and electric under one roof

Best for: Oil-heat households and large-home boiler / burner work in western Nassau.

• Deep oil-heat and boiler expertise
• Strong service-contract program
• Established 24/7 dispatch into Great Neck / Manhasset / Port Washington

Best for: Same-day no-heat / no-cool service calls when scheduling is the priority.

• Aggressive same-day scheduling across Nassau
• Multi-trade dispatch (HVAC + plumbing)
• Wide footprint into Levittown, Hicksville, Massapequa

Hempstead, North Hempstead, Oyster Bay, Long Beach, and Glen Cove each run their own building departments with different HVAC permit fees ($150–$450) and inspection windows. Local Nassau contractors handle the paperwork — out-of-county shops often won't.

Any home-improvement contractor working in Nassau must hold a Nassau County Office of Consumer Affairs home-improvement license. Verify the license is in the contractor's legal entity name, not a sales rep's name.

Nassau is fully inside PSEG-LI territory. Heat-pump rebates run $4,000 market / $7,500 income-qualified flat — but only when filed by a Participating Contractor with Manual J at 100–120% of design load.

Long Beach, Atlantic Beach, Island Park, Freeport, Baldwin Harbor, and Bay Park see accelerated condenser corrosion. A Nassau contractor with coastal experience specs coated coils and elevated pads as standard, not upcharge.

Garden City

Pre-war stock with undersized return-air paths. Manual D matters more than equipment brand.

1. Home+ Air and Heat
2. T.F. O'Brien
3. Universe

Levittown

1947–1955 Cape Cod / ranch stock. Tight attics and original ductwork are the install constraint.

1. Home+ Air and Heat
2. Universe
3. All Week

Hicksville

Mid-century split-levels with mixed retrofit ductwork. Sizing discipline beats brand badge.

1. Home+ Air and Heat
2. All Week
3. T.F. O'Brien

Massapequa / Massapequa Park

Coastal-adjacent South Shore. Salt-air exposure shortens uncoated condenser life.

1. Home+ Air and Heat
2. Universe
3. All Week

Long Beach / Atlantic Beach

Direct salt-air zone. Coated coils and elevated pads should be standard, not upcharge.

1. Home+ Air and Heat
2. Universe
3. All Week

Freeport / Baldwin

South Shore canal-front and post-Sandy retrofits. Confirm equipment elevation on every quote.

1. Home+ Air and Heat
2. Universe
3. T.F. O'Brien

No email required — we'll call you.

Who is the best HVAC contractor in Nassau County?

Home+ Air and Heat ranks #1 for Nassau homeowners on the 6 criteria we use across Long Island: NATE certification, Manual J / D / S discipline, verified review profile, parts + labor warranty, transparent pricing, and 24/7 dispatch. T.F. O'Brien (Mitsubishi Diamond Elite), Universe Home Services (multi-trade), Skaggs-Walsh (oil heat), and All Week (same-day) round out the strongest established Nassau options.

Do Nassau County HVAC contractors need a license?

Yes. Any home-improvement contractor working in Nassau must hold a Nassau County Office of Consumer Affairs home-improvement license. Verify the license number on the written estimate matches the contractor's legal entity name. A salesperson's name on the license is a red flag.

What HVAC company does PSEG-LI recommend in Nassau?

PSEG-LI does not 'recommend' contractors — they maintain a Participating Contractor list for the Home Comfort rebate program. Any enrolled contractor can file the $4,000 market or $7,500 income-qualified heat-pump rebate at install. Enrollment is a paperwork bar, not a quality bar — verify Manual J, NATE certification, and warranty terms separately.

How much does HVAC installation cost in Nassau County in 2026?

A standard central AC replacement in Nassau runs about $7,500–$12,500 installed. Full system replacement (AC + furnace or air handler) is $12,000–$22,000. Cold-climate heat-pump conversions run $14,000–$28,000 before PSEG-LI and National Grid rebates. Coastal Nassau (Long Beach, Atlantic Beach) adds $400–$900 for coated-coil and pad-elevation upgrades.

Which Nassau HVAC contractors install Mitsubishi Hyper-Heat?

Home+ Air and Heat and T.F. O'Brien (Mitsubishi Diamond Elite) are the strongest Mitsubishi Hyper-Heat installers in Nassau. Confirm the model number on the proposal — MXZ-SM, MXZ-SVHZ (Hyper-Heat), and MSZ indoor heads each carry different efficiency and cold-climate ratings.

How do I verify a Nassau HVAC contractor's reviews are real?

Open the reviewer's profile. A real local reviewer has reviewed 5+ unrelated local businesses (restaurants, dentists, dog walkers) in Nassau. A fake or paid reviewer typically has 1–3 reviews, all for HVAC or home-services companies, often clustered in the same week or month.