Savoy Heat Pump Conversion: 1952 Ranch Gas-to-Electric Transition

Case study summary: 1952 mid-century ranch home in Kirkwood’s Savoy neighborhood; complete conversion from gas furnace + separate AC to electric cold-climate heat pump with supplemental electric resistance backup; replaced 2005-vintage gas furnace and 2008-vintage AC with new Carrier Infinity 24 cold-climate heat pump (3-ton, rated heating to -10°F outdoor temperature); total project cost $19,800 with $1,600 Ameren Missouri rebate netting effective customer cost $18,200; completed in 1.5 days during April 2026. Outcome: complete electrification of home heating; reliable cold-climate heating performance during shoulder season testing; estimated $400-$600 annual savings vs. previous gas heating costs; customer satisfaction high with operational simplicity of single-system heating + cooling.

The Home

• Built: 1952
• Style: Mid-century ranch (Cape Cod variation)
• Location: Savoy neighborhood, Kirkwood, MO 63122
• Size: 1,680 sf main level plus 800 sf finished basement office (2,480 sf total conditioned)
• Construction: Wood frame with cedar siding (original); attic and basement insulation upgraded in 2019 (R-50 attic, R-19 basement); original windows replaced with double-pane vinyl in 2014; air sealing improvements completed during 2019 insulation work
• Existing heating: Trane XR80 (80,000 BTU/hr 80% AFUE single-stage forced-air gas furnace from 2005, 21 years old at time of conversion)
• Existing cooling: Trane XR13 2.5-ton AC from 2008 (18 years old, R-410A refrigerant in serviceable condition but past mid-life)
• Electrical service: 200 amp main panel with available capacity (verified during initial assessment)
• Ductwork: Original 1952 sheet metal in basement; serviceable condition; some joint sealing completed during 2019 attic insulation project

The Situation

Customer contacted us in February 2026 with explicit interest in heat pump conversion. Customer drivers:

• Environmental priorities: customer wanted to reduce home’s fossil fuel use; has solar panels installed on home (2022) covering approximately 80% of annual electricity consumption; sees heat pump conversion as extending solar coverage to space heating
• Ameren Missouri rebate availability: customer aware of utility rebates available for heat pump installations and wanted to take advantage
• Equipment age coincidence: both furnace (21 years) and AC (18 years) approaching end of service life within similar timeframe, making combined replacement timing economical
• Insulation/air sealing investment: 2019 envelope improvements substantially reduced home’s heating load, making heat pump capacity more feasible than would have been the case before improvements
• Solar offset potential: with electric heating replacing gas heating, the home’s solar panels could offset more total energy use

Manual J analysis with improved envelope:

• Heating load at 3°F design temperature: 44,000 BTU/hr (significantly reduced from approximately 60,000 BTU/hr load on original uninsulated home)
• Cooling load at 94°F design temperature: 28,800 BTU/hr
• Heat pump sizing approach: 3-ton (36,000 BTU/hr cooling capacity at 95°F) cold-climate heat pump with sufficient heating output at moderate cold temperatures to handle most winter operation; electric resistance backup for extreme cold

The Equipment Selection

Carrier Infinity 24 Cold-Climate Heat Pump (Selected)

• Outdoor unit: Carrier Infinity 24 variable-capacity heat pump (model 25VNA8)
• SEER2: 24.0
• HSPF2: 11.0
• Heating capacity ratings: 36,000 BTU/hr cooling at 95°F; 32,800 BTU/hr heating at 47°F; 30,000 BTU/hr heating at 17°F; 24,000 BTU/hr heating at 5°F; 18,000 BTU/hr heating at -10°F (rated low-temperature heating capacity)
• Refrigerant: R-454B
• Technology: Inverter-driven variable-capacity scroll compressor with intelligent defrost optimization for cold-climate operation
• Communicating system: Carrier Infinity Touch Thermostat integration
• Warranty: 10-year parts

Carrier FE4ANB006 Variable-Speed Air Handler (Selected)

• Type: Variable-speed ECM blower air handler with integrated 10kW electric resistance heating element
• Resistance backup: 10kW (34,120 BTU/hr) auxiliary heating for extreme cold conditions or rapid recovery scenarios
• Why air handler vs. furnace: heat pump conversion eliminates gas service to heating equipment; air handler with electric resistance backup is standard configuration for all-electric heat pump installation

Carrier Infinity Touch Thermostat

• Smart thermostat with Wi-Fi connectivity, learning algorithms, weather data integration
• Outdoor temperature lockout configuration: auxiliary electric resistance heat blocked above 35°F outdoor temperature to ensure heat pump handles primary heating; resistance heat allowed below 35°F as needed for capacity

Alternative Equipment Considered

• Mitsubishi Hyper-Heat ductless: Could have provided ductless approach but customer wanted ducted system maintaining existing distribution
• Trane XV20i heat pump: Competitive equipment; selected against based on customer preference for Carrier brand familiarity and dealer support
• Lennox SL25XPV heat pump: Highest-efficiency option but premium pricing exceeded customer budget after rebate
• Hybrid configuration (heat pump + gas furnace backup): Considered for cold-snap reliability but customer’s environmental priorities favored fully electric configuration; cold-climate heat pump capability made fully electric feasible

The Project Scope

Pre-Installation

• Ameren Missouri rebate application: Submitted application for Carrier Infinity 24 cold-climate heat pump qualifying for $1,600 rebate (24+ SEER2 plus 11+ HSPF2 plus cold-climate certification); pre-approval obtained before installation
• Kirkwood Public Works permit: Pulled within 4 business days; mechanical permit covers HVAC change and electrical permit covers panel modifications
• Equipment ordering: 8 business days for Carrier Infinity 24 heat pump and Carrier variable-speed air handler with electric resistance heating element
• Gas service deactivation coordination: customer coordinated with Spire Missouri to schedule gas service deactivation for heating equipment after installation completion; gas service retained for water heater and kitchen range (not yet electrified)

Installation Day 1 (April 7, 2026)

• Existing equipment isolation and shutdown
• Gas line capping at heating equipment (gas service to remain active for water heater and kitchen range, but disconnected from heating equipment)
• Refrigerant recovery from existing R-410A AC system (proper EPA Section 608 recovery)
• Existing furnace and AC removal
• Existing line set assessment: serviceable condition, retained for new equipment with proper cleaning and pressure testing
• New air handler placement in basement (same location as previous furnace)
• Electric resistance heating element wiring: 50-amp dedicated circuit installation from main panel to air handler heating element
• Outdoor heat pump placement on existing concrete pad
• Refrigerant line connections at outdoor unit and indoor air handler
• Condensate management: existing condensate drain location used (no condensate pump needed)
• End of Day 1: equipment installed but not commissioned

Installation Day 2 morning (April 8, 2026)

• Refrigerant system commissioning: nitrogen pressure test, vacuum pull to 500 microns or below, refrigerant charge per equipment specifications
• Subcooling and superheat verification at outdoor unit
• Carrier Infinity Touch Thermostat installation and configuration: outdoor temperature lockout for auxiliary heat set at 35°F, heating/cooling setpoints configured per customer preferences
• Heat pump operation verification: cooling mode performance (delta-T verification), heating mode performance (delta-T verification at moderate outdoor temperature during installation), auxiliary resistance heat operation (brief verification of resistance element function)
• Defrost cycle verification: equipment operated in conditions allowing defrost cycle observation; defrost optimization confirmed
• Customer walk-through: explained operation, smart thermostat configuration, expected operation across seasons (heat pump primary, resistance backup for extreme cold or rapid recovery), maintenance schedule, warranty registration
• Documentation completed: Ameren Missouri rebate paperwork submitted including installation completion verification, Carrier warranty registration, manufacturer documentation provided to customer
• Final cleanup and customer sign-off (early afternoon Day 2)

Inspection (April 13, 2026)

• Kirkwood Public Works inspector visit 5 business days after installation
• Electrical inspector visit same day verified 50-amp circuit and panel modifications
• Installation passed both inspections without modifications

The Pricing

• Carrier Infinity 24 heat pump outdoor unit: $7,200 equipment cost
• Carrier FE4ANB006 variable-speed air handler with 10kW resistance heat: $3,400 equipment
• Carrier Infinity Touch Thermostat: $480
• Installation labor (1.5 days, 2 technicians): $3,400
• Electrical work (50-amp circuit, panel modifications): $880
• Gas line cap and disconnect: $180
• Refrigerant work (R-410A recovery, R-454B charge): $480
• Mechanical permit fee through Kirkwood Public Works: $220
• Electrical permit fee: $140
• Old equipment removal and disposal: $280
• Refrigerant line set cleaning and pressure testing: $240
• Carrier Infinity commissioning materials: $200
• Ameren rebate application processing: $80
• Miscellaneous fittings, hardware, and consumables: $240
• Total project cost (gross): $19,800
• Less Ameren Missouri rebate: -$1,600
• Net customer cost: $18,200

This pricing fell within our standard range for similar cold-climate heat pump conversions ($17,000–$24,800 for 3-ton cold-climate heat pump with electric resistance backup serving 2,000-2,800 sf home).

The Outcome

Shoulder Season Performance (April-May 2026)

System operated continuously during first two months providing both heating (during cool spring nights) and cooling (during warm late-spring days):

• Heating mode operation: System maintained setpoint reliably during early-spring cold snaps with outdoor temperatures dropping to 28°F; auxiliary resistance heat engaged briefly during one cold snap (overnight low 22°F) to assist heat pump capacity during morning recovery
• Cooling mode operation: System maintained setpoint during early warm weather with outdoor temperatures reaching 88°F; variable-capacity operation provided extended cycles at lower output
• Defrost cycles: Equipment performed automatic defrost cycles as expected during cool/humid conditions; brief 2-3 minute defrost periods didn’t affect comfort

Energy Performance (Projected)

• Previous winter gas consumption (Nov 2024 – Mar 2025): approximately 980 therms at $1.20/therm ($1,176 gas heating cost)
• Estimated heat pump winter electricity consumption: approximately 4,200-5,400 kWh additional vs. previous winter (estimated based on heating load and HSPF2 efficiency)
• At customer’s actual electricity rate: approximately $0.14/kWh effective rate after solar offset, equating to $590-$760 winter heating electricity cost
• Estimated annual heating cost savings: $400-$600 ($1,176 gas baseline vs. $590-$760 estimated heat pump cost)
• Solar offset additional benefit: customer’s solar panels provide additional electricity production that may further reduce net heating cost during shoulder seasons; full annual operating cost data will be available after first complete annual cycle

Customer Feedback

Customer reported high satisfaction with several aspects: equipment operation noticeably quieter than previous gas furnace (variable-capacity heat pump and ECM blower both running at lower output most of the time); smart thermostat integration valuable for monitoring operation and adjusting setpoints; gas service still available for water heater and kitchen range (gradual electrification path rather than all-at-once); reduced fossil fuel use aligning with environmental priorities; Ameren rebate processing handled smoothly by us with minimal customer involvement.

Ongoing Service

Customer enrolled in our maintenance plan covering the new heat pump system; first cooling-season service visit scheduled for July 2026 including hot-weather performance verification; annual fall maintenance scheduled for verification before heating season demand.

Frequently Asked Questions

Will a heat pump actually work in St. Louis winter cold?

Yes — cold-climate heat pumps work reliably in St. Louis climate. St. Louis is in ASHRAE Climate Zone 4A (mixed-humid) with 99% winter design temperature of 3°F — this is well within the operating range of modern cold-climate heat pumps which are rated for heating capacity down to -10°F or lower outdoor temperatures. Carrier Infinity 24 (the equipment installed in this case study) rated heating capacity profile: 32,800 BTU/hr at 47°F outdoor; 30,000 BTU/hr at 17°F; 24,000 BTU/hr at 5°F; 18,000 BTU/hr at -10°F. Home’s design heating load: 44,000 BTU/hr at 3°F (after envelope improvements). Coverage analysis: at 47°F outdoor (typical winter conditions), heat pump provides 32,800 BTU/hr vs. typical load of 18,000-22,000 BTU/hr (comfortable margin); at 17°F outdoor (cold-snap conditions), heat pump provides 30,000 BTU/hr vs. design-condition load (need supplement from electric resistance backup for extended cold periods); at 5°F outdoor (Polar Vortex conditions), heat pump provides 24,000 BTU/hr requiring 20,000 BTU/hr resistance heat to meet full load. The system handles approximately 90-95% of annual heating energy from heat pump operation, with 5-10% from electric resistance backup during coldest periods. This is the standard cold-climate heat pump operating profile and is reliable for St. Louis climate. Operating cost economics depend on specific climate, electricity rates, and gas rates — for this customer with solar panels offsetting electricity costs, conversion economics worked out favorable; for customers without solar in higher electricity rate areas, gas-vs-heat-pump economic comparison varies.

How does the Ameren Missouri rebate work?

Ameren Missouri offers utility rebates for high-efficiency HVAC equipment installations as part of their energy efficiency programs. Rebate amounts vary by equipment type and efficiency rating, with cold-climate heat pumps receiving substantial rebates ($1,600 in this case study for Carrier Infinity 24 meeting 24+ SEER2, 11+ HSPF2, and cold-climate certification requirements). Process: contractor (us) handles rebate application with customer authorization; pre-approval obtained before installation to ensure equipment qualifies and rebate is available; installation completion documentation submitted to Ameren for rebate processing; rebate paid to customer within 6-12 weeks of application approval (typically 8-10 weeks in practice). Rebate amounts current as of 2026 (subject to program changes): basic heat pump installations $400-$800 depending on efficiency; cold-climate heat pump installations $1,200-$2,000; ductless mini-split installations $400-$1,200; thermostat upgrades $50-$100 standalone. Eligibility: equipment must be installed by qualified contractor; equipment must meet specific efficiency thresholds; customer must be Ameren Missouri customer; rebate paperwork must be submitted within specific timeframes. We process rebate paperwork as part of standard installation service for qualifying equipment — customer doesn’t need to navigate the application process. Other utility programs: Spire Missouri (gas utility) and Cuivre River Electric Cooperative offer additional rebates for some equipment types; we check applicable programs during quote development to identify all available rebates.

Why not keep gas furnace as backup instead of electric resistance?

Hybrid configuration (heat pump + gas furnace backup) was an option we discussed with the customer during quote development. Hybrid pros: gas furnace provides higher capacity during extreme cold without electrical capacity issues; existing gas service already available; gas heating costs may be lower than electric resistance heating during peak winter conditions when heat pump efficiency is reduced. Hybrid cons: maintains fossil fuel use that customer wanted to eliminate; equipment complexity with both gas furnace and heat pump increases initial installation cost and ongoing maintenance scope; gas service capacity may need verification; auto-changeover between heat pump and gas backup requires sophisticated control logic. For this customer’s stated environmental priorities, full electrification was the better fit despite slightly higher peak-winter operating costs. Customer accepted that extreme cold-snap periods would use electric resistance backup (less efficient than gas heating during those specific periods) in exchange for eliminating fossil fuel use for heating. Solar panel offset for electricity also influences the economic comparison: customer’s solar panels offset approximately 80% of total annual electricity consumption, meaning the marginal cost of electric heating is lower than the nominal $0.16/kWh utility rate would suggest. For customers without strong environmental priorities or solar offset, hybrid configuration is often the better economic and operational choice in St. Louis climate; for environmentally-motivated customers with solar, full electric is feasible and aligns with broader home electrification goals. We provided both options during quote development with explicit operational and economic framing so customer could choose based on priorities.

What’s the deal with electric resistance backup heat?

Electric resistance backup heat in a heat pump installation provides supplemental heating during extreme cold conditions when heat pump capacity alone is inadequate. How it works: heat pump operates as primary heat source during most winter conditions (typical 5°F to 50°F outdoor temperatures); when outdoor temperature drops below the heat pump’s effective operating range or when heating load exceeds heat pump capacity, electric resistance heating elements engage automatically; thermostat logic controls the changeover and ensures smooth operation. Backup configurations: 5-15kW electric resistance heating elements standard for residential installations (this case study used 10kW); 10kW provides 34,120 BTU/hr of supplemental heat — sufficient with heat pump capacity to handle home’s full design load at design temperature. Outdoor temperature lockout: smart thermostat configured to lock out resistance heat above moderate outdoor temperature (35°F in this installation) ensuring heat pump handles primary heating without resistance heat engaging unnecessarily; below lockout temperature, resistance heat is available when heat pump capacity is exceeded. Operating cost: resistance heat is less efficient than heat pump operation (coefficient of performance 1.0 for resistance vs. 2.5-4.0 for heat pump depending on outdoor temperature); during cold-snap conditions when resistance heat is running, operating costs are higher than they would be with gas heating; over full heating season, resistance heat typically accounts for 5-15% of total heating energy use, so the operating cost impact is modest. Maintenance: resistance heating elements are simple devices with very low failure rates (typically last 20-30+ years with no maintenance); periodic verification during annual maintenance ensures elements remain functional for use when needed.

How long until you fully electrify the rest of the home?

This customer plans gradual electrification over several years rather than all-at-once conversion. Current state (after this installation): heating fully electrified via heat pump; cooling continues to be electric (always was); water heating still gas (planned for conversion within 3-5 years to heat pump water heater); kitchen range still gas (longer timeline for conversion based on cooking preferences); clothes dryer already electric. Customer’s electrification timeline reasoning: spread capital costs across multiple years rather than concentrating all at once; allow gas appliances to reach natural end of service life before replacing rather than premature replacement; assess actual operational satisfaction with each electrification step before proceeding to next; maintain gas service availability during transition period in case of supply disruptions. Solar panel system sizing was done in 2022 anticipating future home electrification; current 80% offset of electricity consumption will become 60-70% offset after heat pump conversion adds substantial winter electricity load, then potentially adjust again when water heater is electrified. For other customers considering electrification path, we discuss complete electrification economics during heat pump quote development including: heat pump water heater installation cost and operational implications; heat pump dryer options if applicable; induction or electric range conversion costs; total electrification investment timeline. Gradual electrification is the typical path for most customers — all-at-once conversion is rare due to capital cost concentration and disruption to multiple home systems simultaneously.

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Contact Purisync Heating and Air

For your heat pump conversion, electrification project, or Ameren Missouri rebate-eligible HVAC installation, contact our 325 N Kirkwood Road office at (314) 338-5111. Initial consultation includes Manual J load calculation accounting for envelope improvements, equipment options across multiple cold-climate heat pump manufacturers, hybrid vs. full-electric configuration analysis, Ameren rebate pre-approval, and written quote with itemized pricing including rebate net-cost calculation.

• Emergency Line (24/7): (314) 338-5111
• Address: 325 N Kirkwood Rd #245, Kirkwood, MO 63122
• Email: info@purisyncheatingairconditioning.xyz
• St. Louis County Mechanical Contractor License: #MC-2014-08439-STL
• Kirkwood Business Registration: #BL-2014-1187
• EPA Section 608 Universal: #608U-2014-385721

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