You have over five degrees F of setback - You may find it more effective to have maybe two degrees F setback. Also, it may be more comfortable.

A 2-degree or more setback will likely trigger the backup to come on. If that is electric, that means your backup electric heating elements come on, maybe they’re staged or you're using gas.

I’m more in the camp of ‘set it and forget it’, in your case that might mean more defrost cycles. Experiment and see.

We usually don’t use setbacks even on vacation but then again our

heat pump is geothermal; no defrost modes - ever!

Also in Eastern Canada.

IMPO

SR

Hi, Paul,

Reducing the setpoint temperature reduces the amount of heat loss from a home (and the amount of heat required to be transferred by the heat pump) in winter. However, the energy savings is muted by your investment in a well-insulated home with low air infiltration. That's a nice problem to have. One potential issue, which others have referred to, is when the setpoint temperature is increased in the morning. If the setpoint and indoor temperatures differ by 2 F or more, your back-up heat will likely come on. For a heat pump, that's usually electric resistance (strip) heaters which are more expensive to operate. To avoid triggering the back up heat, you'd need your Ecobee thermostat to gradually increase the setpoint while you sleep to avoid the back-up heat from coming on. It may or may not be able to do that.

On a separate, but related note, your low air infiltration rate requires that you install a fresh air ventilation system to maintain indoor air quality. You should have an HRV or ERV installed which supplies fresh air to your home. If you don't I suggest you make that a priority.

If you are going to be away for several days, then setting back the temperature will save money even if the electric resistance heat comes on.

The Ecobee may have a setting which controls when the back heating comes on. That may be worth investigating.

See Ecobee Smart SI: Installation and use

• If Allow HP with Aux Heat is "Yes", the auxiliary (i.e., expensive) heat won't turn on for 30 minutes after the compressor starts.
• Stage 2 Temp Delta will prevent the auxiliary heat from turning on unless the current temperature is more than N degrees below the desired temperature (If N = 6°F, the auxiliary heat wouldn't turn on during the switch from 64.4°F to 69.8°F).
• Max Outdoor Temperature locks out auxiliary heat if the outdoor temperature is above a value you set.