11.2 Climate, Resources & Adding a City Not in EDGE

11.2 Climate, Resources & Adding a City Not in EDGE

Exam Focus: Sub-topic 3.3 "Climate and resources" and sub-topic 4.1.3 "Adding a new city where it is not in EDGE" are both explicitly named in the official outline. The second is a favourite because it has a precise, published procedure that candidates either know or guess at.

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The Location Data EDGE Holds

For all cities built into the software, EDGE stores:

Note the split: the first five are climate, the last two are resources. Both are location-specific and both are loaded automatically when the city is selected.

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The Procedure When Your City Is Not in EDGE

EDGE covers a very large number of cities but not every one. The Methodology Report gives the procedure directly:

If a city is not included as an option, then a city that is nearby or similar in weather can be used as the location. In such a case, the monthly average outdoor temperature, latitude and average annual rainfall data should be updated under the key assumptions for the base case to match the city where the project is located.

Breaking that into practice:

Step 1 — Select a proxy city

Choose a city that is either geographically nearby or similar in weather. Similar-in-weather is often the better test: a coastal city 200 km away across a mountain range may be a far worse proxy than a climatically matched city 800 km away. Document the reasoning, because the Auditor will ask why that proxy was chosen.

Step 2 — Update three key assumptions to the real project location

Under the key assumptions for the base case, override:

1. Monthly average outdoor temperature
2. Latitude
3. Average annual rainfall

Latitude matters more than candidates expect: it drives solar geometry, which drives solar gain through glazing, the effectiveness of horizontal shading, and the yield calculation for solar water heating and photovoltaics. A proxy city three degrees of latitude away produces a materially different sun path.

Step 3 — Evidence the override

Supply the source of the substituted values — national meteorological service data, a recognised climate database, or airport station records — as part of the submission. An unsourced manual override is the kind of input an Auditor will not approve.

And note the moving target

The Methodology Report adds that climatic conditions for more cities are continuously being added. A city unavailable at the start of a long design programme may be available by the time the project registers, so re-check rather than assuming.

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Grid Carbon Intensity: The Most Misread Resource Variable

Grid carbon intensity converts energy savings into emissions savings. It does not affect:

• the kilowatt-hours saved,
• the percentage energy saving,
• whether the project meets the 20% or 40% threshold.

It affects only the reported tonnes of CO₂ avoided. Two identical buildings saving 250,000 kWh per year report the same energy performance in EDGE, but the one on a coal-heavy grid reports far larger avoided emissions.

This is the correct answer to a common client question: "our grid is going renewable, will our EDGE rating drop?" No. The rating measures the building. The carbon story changes; the certification does not.

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Utility Costs: Defaults and Overrides

EDGE seeds default average local energy and water costs, and teams may enter project-specific tariffs. Two cautions:

1. Use the tariff the project actually pays. Commercial, residential and industrial tariffs differ, and some markets apply block or time-of-use structures. Entering a national average when the project is on an industrial tariff produces a payback figure the client cannot reproduce.
2. Tariffs move the money, never the physics. Changing a tariff changes utility savings, payback and internal rate of return. It cannot change the percentage energy or water saving, and therefore cannot rescue a project that is short of a threshold.

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Rainfall and the Water Category

Annual average rainfall is the single climate variable most directly wired to a savings measure. EDGE calculates harvestable rainwater as catchment area multiplied by rainfall depth, then adjusted by a filter coefficient assuming 20% losses and by the roof runoff coefficient. In a city with 2,000 mm annual rainfall a modest roof supplies a meaningful share of non-potable demand; in a city with 150 mm the same system is close to decorative. Check the rainfall figure before proposing rainwater harvesting as a route to the 20% water threshold, and note that seasonality matters commercially even though EDGE works from the annual figure — a monsoon-concentrated 1,200 mm demands far more storage than the same depth spread evenly.