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Diseasel300 · #5 12-29-2019, 02:25 PM

Adding my experience on a central system in central Texas.

My house has a central heat-pump and the cost reduction from it is pretty amazing. The old system was a 5-ton Ruud R22 A/C with electric resistance heat. The original rating was 21KW of electric heat and the first winter I lived in this house I could literally hear my electric meter screaming in agony every time it ran. Average electric bill ran me ~$450-500/mo with the thermostat set at 65˚ and a cold house.

The following spring I had loose fill insulation blown in the attic to a depth of 18". That winter I was comfortable with disabling 1/3 of the heat strips and had an average electric bill ~$250 with the thermostat set at 68˚. House was more comfortable, but if I turned the thermostat up, the electric bill went up with it.

Third year I lived here the compressor died on the old unit, it made it 21 years, so a hell of a lifetime in Texas. The new unit that went in was a matched 3 ton ComfortMaker 15 SEER heatpump unit. Despite being a smaller capacity, both pieces of equipment are *HUGE* compared to the old 5 ton that was pulled out.

Since the new unit went in, the electric bill has plummeted. Summers, I average somewhere around $90-100/mo, winters I average anywhere from $75-120/mo depending on how cold it is. We typically see overnight temps around 20F and I keep the house set to 68F. The house was built in 1959 and still has all the original doors and windows, and likely very poor insulation in the walls, but with the heatpump and the attic insulation, it stays very comfortable year-round. Gas is not run to this part of the neighborhood since it was built during the "Atomic era" and everything was new, clean, and electric.

Couple tips to minimize the electric bill with a heat pump:
1: Hose out the condenser coils twice a year. Spring and fall. You'd be surprised how much dirt collects and how much it impacts how the unit runs. Dirt buildup in the winter results in premature frost accumulation on the coil and will trip the unit into defrost way too often (defrost turns on the electric heat strips until the cycle is complete).

2: Leave the temperature setting on the thermostat constant. Don't fall into the trap of turning the temperature up/down at night or when you leave the house. With the heat pump, you'll blow all of your savings by heating or cooling the house back to the changed setpoint. Remember, you're not heating the air only, you're also heating the walls, floors, furniture, and any other mass in the house.

3: Run a thick (2-4") MERV-8 or higher filter. If the unit is sized properly, it should run a fair amount of time. The thick high-filtration filter will cut down considerably on the dust in the house and will slow down the airflow through the system enough to blow fairly warm air in the winter. Once the coil warms up, mine blows ~110-120˚ out of the farthest vent when 32F outside.

4: Use a digital thermostat and set the auxiliary heat delay to 4˚ instead of the default 2˚. It will make the system wait significantly longer to turn on the electric heat for a boost and will negate the electric heat coming on if you bump up the temperature in the house a degree or two.

The modern R410 systems are so much better at being heatpumps than the old R22 systems were. The limitation of them no longer working well below 40F are long gone.