Mini Split vs Central Air Cost Calculator

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Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

Mini-split indoor zone: One indoor head or separately controlled area served by a ductless mini-split system.

Ductwork for central air: The condition of the air ducts central air would use. The selected duct cost is added only to the central air estimate.

SEER2: A cooling efficiency rating. In this calculator, a higher SEER2 lowers estimated electricity use for the same cooling load.

Full-power cooling hours per year: The yearly hours used to turn system size into estimated cooling energy. It is a full-power equivalent, not every hour the system fan runs.

Sizing shortcut: The number of sq ft assigned to one ton of cooling for a rough planning size.

Ton: A cooling capacity unit. This calculator uses 12,000 Btu per hour per ton.

kWh: Kilowatt-hour, the unit most electric bills use for electricity use.

Cost gap: Central air cost minus mini-split cost. Positive means central air costs more. Negative means mini-split costs more.

Mistake: Entering lot size or unfinished space in Home size.
Fix: Use only the cooled sq ft for Home size.

Mistake: Picking Good existing ducts for Ductwork for central air when ducts need sealing, repair, replacement, or do not exist.
Fix: Choose the Ductwork for central air option that matches the work central air would need.

Mistake: Leaving Electricity price at the default when your utility rate is much higher or lower.
Fix: Enter the $ per kWh from your electric bill in Electricity price.

Mistake: Treating Mini-split indoor zones as outdoor units.
Fix: Count indoor areas or heads for Mini-split indoor zones, such as living room plus bedrooms.

Mistake: Comparing a quote with a different Central air efficiency or Mini-split efficiency than the calculator uses.
Fix: Enter the SEER2 ratings from the quotes in Central air efficiency and Mini-split efficiency.

Mistake: Reading Installed cost gap as the full long-term answer.
Fix: Also check Total cost gap over selected years because lower upfront cost can be partly offset by Yearly cooling bill gap.

• This is a planning estimate, not a contractor quote. Real bids can change because of equipment brand, line-set length, electrical work, permits, access, ceiling height, insulation, and local labor.
• The Estimated cooling size used comes from Home size divided by Sizing shortcut. A real system size should come from a load calculation for the home.
• Cooling energy is simplified with SEER2, full-power cooling hours, and Electricity price. It does not model part-load behavior, thermostat settings, humidity control, shade, or duct leakage.
• Energy costs include cooling electricity only. Heating, maintenance, filters, repairs, financing, rebates, tax credits, and equipment lifespan are not included.
• Ductwork costs apply only to Central air estimated installed cost. Mini-split estimates do not include ductwork, but they may need other work not listed here.
• Local price level uses fixed planning multipliers. It cannot know your exact market, contractor workload, or material pricing.
• Mini-split indoor zones are limited to the choices in the calculator. Homes with more zones may need a custom estimate.

How the comparison is calculated

The calculator estimates both systems from the same Home size, Local price level, Electricity price, and comparison period. It then subtracts the mini-split result from the central air result for each gap.

estimated_tons = home_sqft / sqft_per_ton

duct_add = 0 if Ductwork for central air is good existing ducts; duct_repair_cost if repair; duct_replace_cost if replace; duct_new_cost if no ducts now

market_multiplier = 0.90 for lower-cost area; 1.00 for average-cost area; 1.15 for high-cost area; 1.30 for very high-cost area

central_installed_cost = (central_base_cost + estimated_tons * central_cost_per_ton + duct_add) * market_multiplier

mini_installed_cost = (mini_base_cost + estimated_tons * mini_cost_per_ton + mini_split_zones * mini_cost_per_zone) * market_multiplier

Cooling energy uses the estimated cooling size, 12,000 Btu per hour per ton, the entered full-power cooling hours, and the entered SEER2.

annual_kwh = estimated_tons * 12000 * cooling_hours_per_year / (seer2 * 1000)

annual_energy_cost = annual_kwh * electric_rate

total_cost_selected_years = installed_cost + annual_energy_cost * compare_years

upfront_cost_gap = central_installed_cost - mini_installed_cost

annual_energy_cost_gap = central_annual_energy_cost - mini_annual_energy_cost

total_cost_gap_over_selected_years = central_total_cost_selected_years - mini_total_cost_selected_years

How to read the signs

Each gap is central air minus mini-split. A positive gap means central air costs more for that line. A negative gap means the mini-split side costs more for that line.

Mini-example

Using 1,800 sq ft, 600 sq ft per ton, good existing ducts, 3 mini-split zones, average local prices, $0.16 per kWh, 900 full-power cooling hours, 15.2 SEER2 for central air, 20 SEER2 for the mini-split, and 10 years gives an estimated size of 3 tons.

central_installed_cost = (3500 + 3 * 1700 + 0) * 1.00 = 8600

mini_installed_cost = (1500 + 3 * 1800 + 3 * 1200) * 1.00 = 10500

central_annual_energy_cost = 3 * 12000 * 900 / (15.2 * 1000) * 0.16 = 341.05

mini_annual_energy_cost = 3 * 12000 * 900 / (20 * 1000) * 0.16 = 259.20

total_cost_gap_over_selected_years = (8600 + 341.05 * 10) - (10500 + 259.20 * 10) = -1081.47

In that example, central air is $1,900 cheaper upfront, but costs about $81.85 more per year for cooling. Over 10 years, the mini-split side is still about $1,081.47 higher because its higher installed cost is not fully offset by the cooling bill difference.