How does high altitude affect propane tankless selection?

MGI’s recommendation: At a cabin near 10,000 feet, choose the model only after a qualified installer confirms its altitude approval and usable hot-water capacity at that address. “Works on propane” is not enough information to make the purchase.

Rinnai’s November 2018 RU-series manual prohibits installation above 10,200 feet and provides distinct altitude settings, including a 7,701- to 10,200-foot range. That is a model-specific example, not approval for every Rinnai heater or every mountain site. Rinnai N-series manual, safety and altitude settings

Start with the verified installation elevation and full proposed model number, including its fuel configuration. Require the applicable manufacturer instructions and any model-specific altitude capacity information. Ask the installer to show how those documents support the proposal.

The sizing assessment should name the fixtures you expect to use together and the incoming water temperature used in the calculation. Require the resulting hot-water flow at your desired temperature, with any altitude adjustment included. A prominent maximum flow number without the conditions behind it does not answer whether two winter showers will work at this cabin.

The fuel and installation plan also need qualified review. Ask who will verify the propane supply, regulator arrangement, gas demand, venting, combustion air, and final operating setup. The propane supplier and installing trade may own different parts of that work; the quote should make those responsibilities clear.

Do not change gas type or installer altitude parameters yourself. The right heater still needs the right installation and commissioning.

For a seasonal property, ask for an approved freeze and outage plan as part of selection. Describe whether the cabin is left unheated, how power outages are handled, and who can reach it in winter. These conditions can change the practicality of a proposed system even when its altitude rating fits.

Compare complete projects, including an alternative water-heating approach if the proposed tankless unit cannot meet the need reliably under the documented conditions. We would rather resolve that before purchase than ask you to change daily routines around an unsuitable system.

Send the address, elevation, fuel type, fixture list, and proposed model to the provider. Confirm service coverage for that address, the exact tankless model, and the required tasks before arranging work.