This is actually more of a problem with heat than cooling. The system doesn't output really hot air like a gas-fired furnace, it's generally closer to the tempe

This is actually more of a problem with heat than cooling. The system doesn't output really hot air like a gas-fired furnace, it's generally closer to the temperature that the thermostat is set to. If you set the temperature differential more than a couple degrees the system will kick in it's auxiliary heating source (usually electric heater strips) which are so much less efficient than the heat pump that any energy savings you gained by setting the temperature back are almost immediately lost.