I have set up a couple of Categories with Energy Intensity for buildings within the commercial sector, e.g. New Office, with Final Energy Intensity of 250 kWh/m2, which decreases over time in an efficiency scenario (using an interp function).

Within the Fuel Share tab, I've allocated this intensity among fuels (electricity 71%, LPG 14%, etc.).

I did not select Useful Energy Analysis (should I?) in the Category with Energy Intensity, because I do not have data on technology efficiencies.

Within my Key Assumptions branch, I have costs for electricity (ZAR/kWh), LPG (ZAR/GJ), etc.

How do I go about setting up Demand Costs within the New Office category with energy intensity?

As an example for LPG, I've tried the following equation: Energy Demand Final Units[GJ, Fuel=Lpg]*Key\Cost LPG[ZAR/GJ]. But I get an error of "Branch/Result Variable: "LPG:Energy Demand Final Units" was used before it had been calculated.

From other options tried, it seems it wants me to enter a cost/m2 explicitly, but this will change as the energy intensity and my fuel costs change.

How do I set Demand Cost within a Category with Energy Intensity, that will link to the progressive decrease in the FInal Energy Intensity and the fuel cost assumptions within Key Assumptions?

Instead of using "Energy Demand Final Units" which is a results variable, use "Total Final Energy Consumption" in your Demand Cost expression. At the moment, you can't specify the units when referencing Total Final Energy Consumption variable, but I believe the default units are GJ. Also, you will need to ensure the value is scaled properly, so I recommend entering Total Final Energy Consumption on its own in the Demand Cost expression and verifying the units and scale first (remember that you can see the demand results in the bottom pane in Analysis View without having to calculate results). After you confirm the scale, input the rest of the expression.

Hope this helps!

Emily