Electric baseboard heat and no cooling left this finished third floor mostly unused. A single-zone Mitsubishi Hyper-Heat system solved both problems, with $1,900 taken off the invoice.
The third floor of this Littleton, MA home had electric baseboard heat and no air conditioning. The finished dormer room had sloped ceilings, but it was uncomfortable in winter and summer, so the homeowner rarely used it.
Extending the existing system to the third floor did not make sense. Running new ductwork or hydronic piping through three floors of finished space would have meant opening walls and ceilings.
Instead, Pespisa installed a single-zone Mitsubishi ductless heat pump sized with a Manual J load calculation.
The new system gives the third floor its own heating and cooling. A $1,250 Mass Save rebate and a separate $650 Heat Pump Accelerator incentive reduced the invoice by $1,900.
The Challenge
Electric Baseboard Heat and No Third-Floor Cooling
The third floor had two separate comfort problems.
- Electric baseboard was the only source of heat.
- There was no air conditioning on the third floor.
- The finished space became especially uncomfortable during hot summer weather.
- Extending the existing heating or cooling system through three finished floors would have required more invasive work.
The homeowner had a finished room but could not comfortably use it throughout the year.
Rather than extending the existing system, we looked at whether one dedicated system could handle both heating and cooling for the third floor.
A Single-Zone Mitsubishi Ductless Heat Pump
We installed a Mitsubishi Hyper-Heat system serving the third floor only.
The project included one outdoor unit, one indoor wall-mounted unit and the refrigerant lines connecting them. No new ductwork was required.
Outdoor Unit
- Mitsubishi MUZ-GX12NLHZ2 single-zone Hyper-Heat system
- 12,000 BTU cooling capacity
- 14,400 BTU heating capacity
- 25.6 SEER2
- 10 HSPF2
- AHRI reference 216801489
- Installed on a raised stand over a new concrete pad for additional snow clearance
Indoor Unit
The Mitsubishi MSZ-GX12NL indoor unit was installed in the finished third-floor space.
Its location allows conditioned air to move across the room without taking up floor space or requiring new ductwork.
Refrigerant Lines and Electrical
The installation also included:
- Insulated copper line set between the outdoor and indoor units
- Dedicated electrical connections
- Service disconnect at the outdoor unit
- Exterior line-set covering for a cleaner finished appearance
Installation and Commissioning
The completed refrigerant lines were pressure tested with nitrogen before the system was placed into service.
The installation process included:
- Nitrogen pressure testing
- Triple evacuation of the refrigerant circuit
- R-454B refrigerant charge adjusted for the actual line-set length
- Heating operation test
- Cooling operation test
The system was commissioned before the project was completed.
Independent Third-Floor Controls
The indoor unit has its own controls, allowing the homeowner to condition the third floor separately from the rest of the house.
That means the space can be heated or cooled when it is being used without changing the temperature on the first two floors.
The electric baseboard serving the area covered by the new heat pump was also disconnected as part of the project.
Why a Single-Zone Heat Pump Fit This Third Floor
A single-zone system allowed us to address the problem where it existed without replacing equipment that was already serving the rest of the home.
We Sized the System With a Manual J Calculation
We completed a Manual J load calculation rather than selecting equipment based on square footage alone.
The calculation helped determine that a 12,000 BTU system was appropriate for the space.
Proper equipment sizing matters. An oversized system can cycle more frequently and may provide less effective humidity control during milder weather.
Mitsubishi Hyper-Heat for a Massachusetts Home
The homeowner needed the system for heating as well as cooling, so we selected a Mitsubishi Hyper-Heat model designed for cold-climate operation.
The installed system provides 14,400 BTU of heating capacity from a 12,000 BTU nominal system.
R-454B Refrigerant
The system uses R-454B refrigerant, a lower-GWP refrigerant used in current-generation HVAC equipment.
We Fixed One Floor Instead of Replacing the Whole System
Nothing on the first or second floor needed to change.
The project addressed the part of the house that needed additional heating and cooling without turning it into a whole-home HVAC replacement.
Heating and Cooling for the Littleton Third Floor
The finished third floor now has independent heating and air conditioning from one ductless system.
The electric baseboard serving the space was disconnected, and the homeowner can condition the room without changing the systems serving the first two floors.
Project Highlights
- Single-zone Mitsubishi Hyper-Heat system
- Heating and cooling for the finished third floor
- 12,000 BTU cooling capacity
- 14,400 BTU heating capacity
- Manual J load calculation used for system sizing
- Electric resistance baseboard disconnected in the served area
- $1,250 Mass Save rebate
- $650 Heat Pump Accelerator incentive
- $897.66 Full Circle Membership discount
- $2,797.66 total reduction from standard pricing
- $6,277.96 final invoice
- Completed June 2026
Littleton Heat Pump Project Details
| Project Detail | Specification |
|---|---|
| Location | Littleton, MA |
| Project Type | Single-zone ductless heat pump, third floor |
| Completed | June 2026 |
| System | Mitsubishi single-zone Hyper-Heat |
| Outdoor Unit | MUZ-GX12NLHZ2 |
| Indoor Unit | MSZ-GX12NL wall-mounted unit |
| Cooling Capacity | 12,000 BTU |
| Heating Capacity | 14,400 BTU |
| Efficiency | 25.6 SEER2 / 10 HSPF2 |
| AHRI Reference | 216801489 |
| Refrigerant | R-454B |
| Previous Heat | Electric baseboard |
| Previous Cooling | None |
| System Sizing | Manual J load calculation |
| Mass Save Rebate | $1,250 |
| Heat Pump Accelerator | $650 |
| Total Off Standard Pricing | $2,797.66 |
| Final Invoice | $6,277.96 |
How $1,900 Came Off the Invoice
This project received a $1,250 Mass Save rebate plus a separate $650 Heat Pump Accelerator incentive.
Both were applied directly to the project invoice, reducing the amount the homeowner had to pay by $1,900.
Qualifying heat pump projects may also be eligible for Mass Save HEAT Loan financing.
Incentive amounts shown reflect this completed June 2026 project. Current amounts and eligibility requirements may vary depending on the property, equipment and available programs.
Considering a Ductless Heat Pump in Littleton, MA?
If part of your home relies on electric baseboard heat, has no cooling, or sits beyond the reach of your existing HVAC system, a single-zone ductless heat pump may provide another option.
Pespisa Company evaluates the space, completes the appropriate load calculations and recommends a system based on the home rather than simply choosing equipment by square footage.
We serve Littleton and communities throughout Middlesex County.