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ResStock Water Heater Options: Condensing or Non-Condensing?

asked 2023-10-23 19:09:34 -0500

sashadf1's avatar

I'm using the latest version of ResStock and buildstockbatch to run some electrification analyses in Maine.

Water Heater Options options_lookup

Is the Propane Tankless option a condensing or non-condensing equipment model?

This affects the propane heating value (LHV or HHV) I choose for calculating annual operating cost and emissions.

It's hard to determine condensing vs. non-condensing just by looking at the EF rating in the measure arguments. For example, the Natural Gas Premium, Condensing option has an EF of 0.82, which is a bit low for a condensing model. Despite that I assume this option is a condensing model because it is explicit in the Option Name.

Advice on the Propane Tankless option would be great.


For furnaces, an AFUE of > 90% would indicate a condensing model. Is there a similar cutoff rule-of-thumb for water heaters and Energy Factor?

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answered 2023-10-23 23:50:43 -0500

sashadf1's avatar

Based on internet research it seems like gas-fired instantaneous (tankless) water heaters have UEFs up to 0.82.

In ResStock the measure argument water_heater_efficiency_type = EnergyFactor, so I converted a UEF of 0.82 to EF using RESNET's 2017 guidelines (below).

I assume a Propane Tankless model would fall under "Instantaneous Gas-Fired Water Heater," and therefore UEF = EF.

Since the EF for the Propane Tankless model in ResStock is 0.82, it's reasonable to conclude it represents non-condensing equipment, but it would be great to get confirmation from the ResStock team.

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Asked: 2023-10-23 19:09:34 -0500

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Last updated: Oct 23 '23