Denver installers disagree about keeping gas backup in my older home. Who is right?

Ask both installers the same questions

Request the heating and cooling load calculations, the local winter design temperature, and the exact indoor and outdoor model numbers. Ask each installer to show the proposed heat output at that condition and explain what will heat the home below it.

Then state your priorities: keep a useful furnace, remove gas use, limit upfront cost, control operating cost, or improve room comfort. Ask which priority the proposal serves and what tradeoff comes with it. A recommendation can be technically sound yet solve a different problem from the one you care about.

Make the backup role specific

If keeping gas, ask when the furnace runs, whether it meets the required heat need, how the controls choose between systems, and what compatible equipment is required. If removing gas heat, ask what replaces that role and whether electrical work is needed.

Ask for a forecast using your current utility accounts and the exact rate plan, including expected backup use. Do not accept “electric is always cheaper” or “heat pumps always cost more” as a forecast.

An old home may need improvements before either option performs as intended. Ask who will assess air leakage, insulation, and existing air distribution, and who owns any separate corrective work. A home's age does not tell us the size of that work.

Know what would change our recommendation

We would lean toward retaining a sound, compatible furnace when the heat-pump proposal relies on it for a clearly justified cold-weather or cost role. We would consider full replacement when the all-electric design documents adequate performance, the electrical and installation needs are resolved, and its costs fit your goals.

If the two proposals use different load assumptions, resolve those assumptions first. Paying for an independent qualified design review can be more useful than collecting a third unsupported opinion.

Your next action is an aligned comparison: same home data, named equipment, backup strategy, full installed scope, and cost assumptions. That lets you choose a plan rather than a position in an argument.