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Understanding Your Home Heating Options: From Legacy Systems to High Efficiency Units and Mini Splits

  • jeffkmgmechanical
  • Aug 31
  • 3 min read

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For homeowners in New Hampshire and Southern Maine, heating isn’t just a comfort it’s a necessity. With winters stretching months and temperatures dipping well below freezing, your heating system plays a major role in your home’s comfort, safety, and operating costs.

As HVAC professionals, we often sit down with customers who want to know:

  • What type of heating system do I have now?

  • Is it worth repairing, or should I upgrade?

  • What are the real savings of high efficiency systems and mini splits?

Let’s break down the different types of home heating systems from the older “legacy” units still found in many homes to today’s advanced high efficiency systems and help you understand costs, benefits, and what matters most to you as a homeowner.

1. Legacy Heating Systems (Older Furnaces and Boilers)

Furnaces (Forced Hot Air)

  • Fueled by oil, propane, or natural gas.

  • Pushes heated air through ductwork and vents.

  • Common in homes built from the 1970s through the early 2000s.

  • Efficiency rating: Many older furnaces operate at 65–75% AFUE (Annual Fuel Utilization Efficiency).

Boilers (Forced Hot Water or Steam)

  • Fueled by oil or natural gas.

  • Circulates hot water through radiators or baseboards.

  • Known for steady, comfortable heat.

  • Efficiency rating: Older boilers may operate at 60–70% efficiency.

The Homeowner Impact: Legacy systems still heat your home, but they burn a lot of fuel compared to modern options. That means higher utility bills, more emissions, and sometimes frequent repairs as parts wear out.

  • Typical lifespan: 20–25 years (furnaces) and up to 30 years (boilers).

  • Warning signs: Rust, odd noises, uneven heating, and skyrocketing fuel bills.

2. Modern High-Efficiency Furnaces and Boilers

High Efficiency Furnaces

  • Today’s gas and propane furnaces achieve 95–98% AFUE.

  • They use condensing technology capturing heat from exhaust gases that older furnaces vent outside.

  • Quieter operation, sealed combustion, and better airflow.

High Efficiency Boilers

  • Condensing boilers achieve 90–95% efficiency.

  • Compact wall-hung options save space.

  • Advanced controls modulate heat output based on demand, saving fuel.

The Homeowner Impact: Moving from a 70% efficient boiler to a 95% model could save hundreds of dollars per year on fuel bills. Over the system’s life, this adds up to thousands of dollars in savings.

  • Rebates & credits: NH Saves often offers rebates for high efficiency systems, plus potential federal tax credits to offset the cost.

3. Mini Splits & Heat Pumps (The Future of Heating)

What They Are: Mini splits and ducted heat pumps use electricity to move heat instead of burning fuel. Modern cold climate heat pumps can heat even when outdoor temperatures drop below zero.

How They Work

  • Outdoor condenser + one or more indoor units (wall, ceiling, or ducted).

  • Provide both heating and cooling in one system.

  • Inverter driven technology runs only as much as needed, saving electricity.

Efficiency & Savings

  • Seasonal efficiency ratings far exceed traditional systems.

  • For many homes switching off oil or propane, annual savings can be 30–50%.

  • Eligible for generous rebates through NH Saves, plus federal tax credits.

The Homeowner Impact

  • Great for homes without ductwork.

  • Excellent zone control (heat/cool only the rooms you use).

  • Quiet, efficient, and environmentally friendly.

4. What’s Most Important to Homeowners

When we talk with customers, three main factors always come up:

Comfort

  • Does the system heat evenly?

  • Are there drafts, cold rooms, or noisy vents?

  • Boilers and mini splits are known for steady comfort; older furnaces often cause hot/cold swings.

Efficiency & Cost

  • High fuel bills? Switching to high efficiency or mini splits reduces operating costs.

  • For homeowners on oil, mini splits are a great hedge against rising fuel prices.

Reliability

  • Legacy systems break down more often and can be costly to repair.

  • High efficiency systems are reliable when properly maintained.

  • Regular maintenance (annual tune-ups) is the best way to extend system life.

5. What to Do Next

  1. Know what you have: Furnace, boiler, or mini split.

  2. Check the age: If it’s 15–20+ years old, replacement should be on your radar.

  3. Get a professional evaluation: An HVAC pro (like KMG Mechanical) can test efficiency, inspect safety, and give you real numbers on repair vs. replace.

  4. Ask about rebates: Don’t leave money on the table. Many upgrades qualify for rebates or federal incentives.

Final Thoughts

Heating technology has come a long way. If you’re living with a system that’s 20 years old, you could be paying 30–40% more each year than you need to. Modern furnaces, boilers, and especially mini splits can dramatically cut costs, improve comfort, and add resale value to your home.

At KMG Mechanical, we help homeowners make the right choice whether that’s squeezing a few more years out of your current system with a tune-up, or installing a brand new high efficiency unit that will pay you back over time.

Call us at (603) 919-7929 or visit www.kmgmechanical.org to schedule your heating consultation today.


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