I have a high efficiency gas furnace along with a heat pump/air conditioner.
I want to change my old Honeywell Chronotherm 111, programmable thermostat with a new Honeywell Proo TH6220D model.
The old one has seven wires the new calls for eight?
Help!

If you have to have 8 pull a additional wire.

Your system only needs 7 wires. The new thermostat shouldn't need more unless it requires a common one for power that the old didn't. If so, you might return it for one that doesn't. There is a great explanation of thermostat wires at https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-frequently-asked-questions-58313.html

If your furnace is in an unfinished basement, pulling a wire may not be that big of a project.