I have a separate post regarding duct sizes but our new unit is using more electricity than older unit. Both are 3.5 ton. Prior unit was a 20 year old 10 seer, new one is 14 seer. The two differences are airflow and cycles. The prior unit would run and run, sometimes for 90 minutes or more at a time. Long run times even in early evenings. The new unit runs between 11 and 14 minutes on 84 degree days. On 92 degree days for maybe 23 minutes

So the new unit cycles a whole lot more. Is that causing my higher electricity usage?

The airflow is much stronger even with a one inch merv 10 filer. The humidity is usually between 45 and 55%. The 55% is normally only in the morning hours until the unit comes on. It is a single stage unit. House is 1700 sq ft excluding sunroom. House gets full sun all day. Airflow is much stronger even if fan is on low. They did turn the new air handler to eliminate an angle in the plenum. The plenum now goes straight up

Thank you


The unit cycling on and off more would have a negligible effect on your usage. Now the air handler is a different store. If the installer upped the size of it than that's where your increase it. That would explain the higher air flow. Most air handlers have different speeds the blower will operate at. Maybe your old unit have a lower speed set and the new unit has a higher setting set. Those motors are usually 1/3 to 1/5 HP and they run all the time the compressor is running unless you have it set to run continually... make sure it's set to "auto". The plenum being rerouted would also help the airflow by eliminating the bend. If the installers replaced the thermostat the calibrations will probably be different and that would also affect the run time of the unit.

  • Thanks, Jack. It stayed a 3.5 so we didn’t increase the tonnage. But the new units push more air plus we improved the plenum. I had read that more cycles use more power because it takes more energy to start the unit than run it. Is that corr? – Dominick Orlando Apr 12 '20 at 16:09
  • The tonnage refers to the compressor unit, usually the outside piece and the air handler is inside. The air handler can be up sized without increasing the tonnage. The current to start the unit is greater but it's only for a few seconds and there's a voltage dip so there's no significant increase in usage. – JACK Apr 12 '20 at 16:30
  • The air handler blower is set to medium but does have a low. Does the low use less electricity and can having it on low cause issues? I have read it could cause the unit to freeze up since enough air won’t be blowing over it? – Dominick Orlando Apr 12 '20 at 16:58
  • The low uses less electricity but yes, it can cause freeze ups and you would probably have to use a lower merv filter. As whole, do you notice it cooling better? – JACK Apr 12 '20 at 18:08
  • Do you think I am safe running it on low if I use a nom pleated type filter? As you know from other post I am testing with an 8” in plenum. Still good airflow but the Honeywell pro 8000 is very sensitive. Still cycles a lot more than old system – Dominick Orlando Apr 12 '20 at 18:31

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