A $6,300 48V Solar-Powered Heat Pump in Climate Zone 4A

Real-World Performance of a 1-Ton DC System in Eastern Pennsylvania

Most solar HVAC systems rely on an inverter to power a conventional 240V mini split.
This system does not.

It is a dedicated 48V DC-native heat pump powered directly from solar and batteries:

Solar → MPPT → 48V battery bank → 48V DC heat pump

No inverter.

Installed in Eastern Pennsylvania (IECC Climate Zone 4A, mixed humid), this system supplements existing HVAC rather than replacing the grid.

Here are the real-world results.

System Photos

1. Outdoor unit

2. Indoor head

3. Victron MPPT 150 60

4. EG4 LL battery rack

5. Combiner box

6. Panasonic EverVolt 360W spec label

7. HotSpot Energy DC4812VRF spec label

System Specifications

Heat Pump

• HotSpot Energy DC4812VRF
• 1 ton (12,000 BTU)
• 48V DC native
• Rated power: 930W
• Max DC input current: 28.5A
• Cost: $2,095 (included indoor + outdoor unit and line set)

Solar Array

• 4 × Panasonic EverVolt 360W panels
• 1.44 kW nameplate
• ~1.9 kW observed peak under ideal conditions

Charge Controller

• Victron BlueSolar MPPT 150/60

Battery Bank

• Initially: 1 × EG4 LL (5.1 kWh)
• Expanded to: 3 × EG4 LL (15.3 kWh total)

Total System Cost

Approximately $6,300+
No inverter required.

Why 48V DC Instead of a 240V Mini Split?

A conventional system requires:

Solar → Battery → Inverter → AC Mini Split

That adds:

• Inverter cost
• Idle draw
• Surge sizing
• Conversion losses

This system eliminates the AC conversion stage entirely.

For a dedicated HVAC load, that materially simplifies architecture.

Performance with 5 kWh of Storage

With a single battery:

• Reliable daytime operation
• Limited overnight runtime
• Rapid depletion during cloudy stretches

Storage was clearly the constraint.

Performance with 15.3 kWh of Storage

After expanding to three batteries:

• Overnight operation became stable
• Depth of discharge normalized
• Voltage stability improved under load

However:

At ~15 kWh of storage, the bottleneck shifted.

Generation, not storage, became the limiting factor.

When It Fails

Approximately four times per year, during:

• Multi-day winter cloud cover
• High-demand, low-irradiance summer events

The system drains to zero.

This is a predictable boundary condition in Climate Zone 4A.

Adding more batteries would not solve extended low-sun events.

Adding more panels would.

More Batteries or More Panels?

After ~15 kWh of storage, daily energy input governs system reliability.

If expanding further, additional solar generation would provide more resilience than additional storage.

That is the core design lesson from this system.

Comparison: 48V DC vs 240V Mini Split

I have also installed a conventional 240V mini split in a separate building.

240V Mini Split

• Pros: simple, unlimited runtime on grid
• Cons: grid dependent, requires inverter if battery-backed

48V DC System

• Pros: direct battery operation, no inverter losses, partial energy autonomy
• Cons: production limited, seasonal variability

This DC system is not a grid replacement.

It is a strategic supplemental solar HVAC system.

Related Planning Resources

• Explore the solar sizing methodology for off-grid HVAC loads to estimate required generation.
• Review the battery storage planning guide for overnight runtime when evaluating storage expansion.
• Compare system design tradeoffs for DC-native and AC-coupled systems before finalizing architecture.
• Use generator backup planning for prolonged low-sun periods to cover rare seasonal deficits.

Key Takeaways

• DC-native HVAC simplifies system design.
• After ~15 kWh of storage, generation becomes the constraint.
• Climate zone matters more than spreadsheet autonomy estimates.
• Supplemental solar HVAC is attainable without whole-home batteries.