Case Study: Small Cottage Heat Pump Conversion in Carter Lake

This case study documents a heat pump conversion for a small lakeside cottage in Carter Lake, replacing aged baseboard electric heat and window AC units with a modern multi-zone ductless mini-split system. The property is a converted summer cottage that the customer recently winterized for year-round occupancy; the existing electric resistance baseboards produced extremely high winter electricity bills while window AC units provided inadequate summer cooling. The case illustrates ductless mini-split installation in small properties without existing ductwork, with substantial federal tax credit utilization for cold-climate heat pump installation.

Customer Situation

The property is a 1958 small lakeside cottage in Carter Lake, 950 sq ft on a 4,800 sq ft lot with substantial Carter Lake frontage. The customer is a single woman in her early 50s who works remotely as a software developer; she purchased the cottage 3 years ago (2022) initially as a weekend retreat from her primary Omaha residence, then made it her year-round home in 2024 after her remote work arrangement became permanent.

Existing equipment:

• 1958 original electric resistance baseboard heaters in each room (8 baseboards total)
• Two window AC units (living room and bedroom) for summer cooling
• No central heating or cooling; no ductwork
• 200-amp electrical service updated 2022 (customer-funded improvement)
• Substantial insulation improvements 2022-2023 (R-49 attic, basement wall, weatherization)

Motivations for heat pump conversion:

• Extreme winter electricity bills with electric resistance baseboards ($400-$600 monthly during peak winter)
• Inadequate summer cooling with limited window AC coverage
• Year-round occupancy made operating cost reduction substantial priority
• Federal Section 25C tax credit availability for cold-climate heat pump ($2,000 cap)
• MidAmerican Energy customer rebate eligibility
• Environmental commitment to reduce energy consumption

Diagnostic Assessment

Consultation by Mark Tran (Cold-Climate Tech, 5 years, ex-Minneapolis experience). Assessment time approximately 2 hours including property evaluation and equipment selection consultation.

Property Heating Load Analysis

• Post-insulation Manual J heating load: approximately 18,000-22,000 Btu/hr (small property with substantial 2022-2023 envelope improvements)
• Cooling load: approximately 12,000-15,000 Btu/hr
• Single-zone vs multi-zone consideration: 4-room layout (living/kitchen open + bedroom + bathroom + utility/laundry) suggests multi-zone for room-level control
• Customer occupancy patterns (remote work in living area, sleeping in bedroom, kitchen activity, infrequent utility room use) supports zone-specific control

Mini-Split Configuration Options

• Option A — Single-zone — one indoor unit in central living area; heat distribution to other rooms passive through doorways. Substantial cost savings ($5,500-$6,500) but limited room-specific control.
• Option B — Two-zone — one indoor unit living area + one indoor unit bedroom. $7,200-$8,800. Sleep area independent control.
• Option C — Three-zone — living + bedroom + kitchen indoor units. $9,500-$11,200. More zone control but possibly excessive for small property.

Customer selected Option B (two-zone) as appropriate balance:

• Bedroom independent control allows lower nighttime sleep temperature
• Living area handles main occupied space during work hours
• Kitchen and bathroom adequately heated/cooled passively from living area
• Utility room can remain unheated (boiler/water heater located there, no occupant comfort needed)

Equipment Selection

• Mitsubishi MXZ-SM24NAMHZ outdoor unit — cold-climate dual-zone heat pump, up to 24 SEER2 cooling, 12 HSPF2 heating, rated heating capacity to -13°F
• Two Mitsubishi MSZ-FH wall-mount indoor units — 9,000 Btu/hr (bedroom) and 12,000 Btu/hr (living area)
• kumo cloud wireless thermostats — smartphone control and zone scheduling
• Existing baseboard heaters retained as backup — deactivated at breaker but available for emergency use during extreme cold periods exceeding heat pump capacity

Installation Execution

Single 8-hour day installation:

• Morning — Equipment delivery; outdoor unit mounting on existing concrete pad (small cottage already had AC pad from prior window unit installation requirement)
• Midday — Refrigerant line routing through accessible exterior wall penetrations to interior locations; bedroom indoor unit installation; living area indoor unit installation
• Afternoon — Electrical work and connections to upgraded 200-amp panel; kumo cloud wireless thermostat installation; system commissioning and refrigerant charging; baseboard heater breaker deactivation (preserving option for future activation if needed); customer walkthrough including smartphone app setup

Results

• Heat pump primary heating — all electric resistance baseboard heating eliminated
• Whole-property cooling — substantial improvement over limited window AC coverage
• Cold-climate capability — rated heating to -13°F well below Omaha design conditions
• Substantial electricity cost reduction — first winter electricity bills approximately 55-65% lower than prior baseboard heating (heat pumps are 3-4× more efficient than electric resistance)
• Zone control benefit — bedroom independent control allows nighttime setback during sleep
• Federal Section 25C tax credit — $2,000 (30% × $2,000 cap for qualifying cold-climate heat pump)
• MidAmerican Energy rebate — $1,200 for cold-climate variable-capacity equipment
• Backup heating retained — baseboards available for emergency activation if needed
• Customer remote work comfort — consistent temperatures throughout work hours support remote work effectiveness

Pricing

Total project cost: $8,400

• Mitsubishi MXZ-SM24NAMHZ outdoor unit (dual-zone cold-climate): $3,485
• Two Mitsubishi MSZ-FH indoor units (9K + 12K Btu/hr): $2,985
• kumo cloud wireless thermostats: $385
• Refrigerant line sets and accessories: $585
• Electrical work and connections: $485
• Installation labor (8 hours): $385
• Baseboard heater breaker deactivation: $35
• System commissioning and refrigerant charging: $35
• Mounting materials and miscellaneous: $20

Net cost after rebates and credits:

• Project cost: $8,400
• MidAmerican Energy heat pump rebate: -$1,200
• Federal Section 25C tax credit: -$2,000
• Net cost: $5,200

Electricity Cost Comparison Analysis

First-year operating comparison (12 months of operation):

• Prior baseboard heating + window AC: approximately $4,800 annual electricity
• New heat pump + minimal supplemental: approximately $1,800 annual electricity
• Annual electricity cost reduction: $3,000
• Payback period on $5,200 net investment: approximately 1.7 years
• Cumulative 15-year electricity cost savings: estimated $45,000+ (assuming modest electricity price increases)
• Equipment expected lifespan: 15-20 years

Why Mini-Splits Work Well for Small Properties

• No ductwork required; substantially lower installation cost than ductwork addition
• Equipment sized for actual property load (smaller equipment, lower capital cost than larger central systems)
• Zone control without complex damper systems; each indoor unit operates independently
• Variable-capacity inverter operation matches small load efficiently (avoids cycling stress of larger central equipment)
• Quiet operation in small properties where equipment noise would be noticeable
• Customer-friendly smartphone control particularly valued by software developer customer

Lessons from This Project

• Small properties (under 1,500 sq ft) often benefit substantially from ductless mini-split systems vs ductwork installation
• Electric resistance baseboard heating produces extreme winter operating costs; heat pump conversion provides substantial savings (55-65% reduction in this case)
• Combined federal Section 25C ($2,000) + MidAmerican Energy ($1,200) = $3,200 incentives substantially reduce capital cost
• Payback periods under 2 years are achievable for electric resistance to heat pump conversions in small properties
• Two-zone configuration appropriate for small properties balancing cost and zone-specific comfort
• Cold-climate heat pump equipment essential for Omaha-area year-round operation

---

Contact Omaha Heating and Air Conditioning

For Carter Lake cottage heat pump conversion, electric resistance to heat pump electrification, small property ductless mini-split installation, or remote-work property HVAC consultation, call our 24/7 line.

• Emergency Line (24/7): (402) 258-6703
• MidAmerican Energy Emergency: 800-595-5325 (Iowa gas/electric)
• 911: for CO detector alarms or fire/smoke situations
• Address: Lake Regency Building, 450 Regency Pkwy #370, Omaha, NE 68114
• Email: info@omahaheatingairconditioning.xyz
• Iowa Plumbing & Mechanical Systems Board License: #B-027841
• EPA Section 608 Universal: #608U-2014-227841

← Back to Case Studies