Mitsubishi Hyper Heat

HVAC performance and power check.

This page tracks the installed Mitsubishi system, expected power draw from the spec sheets, and what the Emporia data should show during hot cooling days and cold winter events.

Outdoor unit

MXZ-SM36NLHZ

36,000 BTU/h Hyper Heat multi-zone condenser.

Downstairs head

MSZ-GX24NL

22,400 BTU/h rated wall-mounted indoor unit.

Upstairs head

MSZ-GX09NL

9,000 BTU/h rated wall-mounted indoor unit.

Expected draw

What the system should use

The outdoor unit is the limiting power device. The two indoor heads add up to about 31.4k BTU/h nominal capacity on a 36k BTU/h outdoor unit, so the pairing is reasonable on paper.

Condition Spec-sheet draw How to read Emporia
Cooling at 95°F ~2.5-3.3 kW at rated/full output A hot-day full call should often land in this range, then modulate down once rooms approach setpoint.
Heating at 47°F ~3.1-3.6 kW Mild winter heating should not look extreme unless the house is recovering from a large setback.
Heating at 17°F ~2.9-3.4 kW rated, ~6.0-6.8 kW max Cold-weather spikes near 6 kW can be normal if the compressor is running hard.
Heating at 5°F ~6.2-6.6 kW max Sustained high winter draw is plausible during cold snaps.
Heating at -13°F ~8.7 kW max This explains why the 45A breaker and the 178.7 kWh winter peak day are not automatically suspicious.

Cooling audit

The 96°F day should have been a valid stress test

Philadelphia-area reporting shows May 19, 2026 reached record heat, with Philadelphia reported at 98°F and nearby Trenton/Wilmington at 96°F. That is close to the Mitsubishi cooling test condition of 95°F outdoor air, so the spec-sheet cooling draw is a fair comparison point.

If Emporia showed low draw

If the house was hot but HVAC stayed far below ~1.5-2 kW, the system may not have been commanding/ramping both zones hard enough.

If Emporia showed 2.5-3.3 kW

That is expected full-output cooling behavior. If comfort was still poor, look at airflow, refrigerant charge, placement, solar gain, attic load, and sizing/distribution.

If Emporia showed high draw all day

The unit was working hard. The next question is whether each head delivered cold air and whether the building shell was gaining heat faster than the system could remove it.

Winter audit

February peak use is explainable, but still worth measuring

The Emporia data shows a 178.7 kWh peak day on February 8, 2026. Regional reporting and alerts show late January and early February 2026 had a serious cold spell in Pennsylvania, so a high heat-pump day is plausible.

  • Expected cold behavior: this outdoor unit can draw around 6-8.7 kW at hard winter output.
  • What would be concerning: high draw during mild outdoor temperatures, short-cycling, weak supply temperatures, or frequent failed setpoint recovery.
  • Best next data: export Emporia HVAC watts for May 19, 2026 and February 8, 2026, plus indoor setpoint, indoor temperature, outdoor temperature, and which heads were calling.

Action checklist

What to check before summer

If it is not cooling the house now, do not assume the answer is only more attic insulation. Prove whether the equipment is producing expected cold air first.

Equipment checks

  • Clean both indoor filters.
  • Wash/clear the outdoor coil.
  • Measure supply-air temperature from each head during full cooling call.
  • Have a tech verify refrigerant charge, fan speed, line-set condition, and no short-cycling.

Building checks

  • Air-seal attic penetrations before adding insulation.
  • Check attic hatch, bath fans, can lights, duct chases, and top plates.
  • Confirm attic ventilation is not blocked.
  • Use R49-R60 as the attic insulation target range if existing levels are below guidance.

Sources