Units in Aire
Every term in Aire has a unit. That unit isn’t just a label—it’s an active part of the model. It travels through formulas, surfaces in views, and appears in exports. When you combine terms in a formula, Aire checks whether the units are compatible and flags the formula if they aren’t. This is the unit system: structured, automatic, and always on.Setting and Changing a Unit
You assign a unit when you create a term. Units are also assigned automatically during model import—Aire reads the unit metadata from your source file and maps it to each term. You can update a term’s unit at any time. When you do, Aire propagates the change through every formula and view that references that term, so nothing goes stale silently. Recognized units (listed in the reference below) unlock automatic conversion and consistency checking. For anything not in the library, units are free-form text—you can express them however your domain requires (kgCO₂e/MWh, MMBTU/hr) without being constrained.
Automatic Unit Consistency Checking
When you write a formula that combines two terms, Aire resolves the resulting unit based on the operation:- Multiplying
MWbyhours→MWh - Dividing
USDbyMWh→USD/MWh - Adding
USDtoUSD→USD
MW to MWh isn’t valid—you can’t add power to energy. Aire catches this. The platform validates that the units in a formula resolve to something coherent, and flags the formula if they don’t.
This validation runs automatically—you don’t configure it or turn it on. It’s part of how every formula is evaluated.
Error Detection and Resolution
When a formula’s units don’t resolve cleanly, Aire surfaces a unit error directly on the term. The error indicates which terms are in conflict and what units are involved. To resolve it, you have two options:- Fix the formula: If the combination genuinely doesn’t make sense, the formula likely has a logic error that needs to be corrected.
- Add an explicit conversion: If the combination is intentional (e.g., normalizing
MWhtoMWover an assumed period), you can introduce a conversion term that makes the unit relationship explicit.
Units as Guardrails
Units act as guardrails at two levels: for your model and for AI. For your model: Unit checking has caught errors in every customer model ingested to Aire to date. These aren’t obscure edge cases—they’re the kind of mistake that’s easy to make in a complex model: a formula that divides where it should multiply, a cost expressed in$/kW when the downstream formula expects $/MW, a percentage applied as a decimal in one place and as a whole number in another. Each of these produces a result that looks plausible but is wrong. Units surface these issues at the formula level, before they propagate into outputs.
For AI: When Aire’s AI suggests or generates formulas, those formulas are subject to the same unit validation as anything you write yourself. A formula the AI produces that combines incompatible units will surface an error just like any other. This means you can evaluate AI-generated formulas with confidence—if the units check out, the formula is at least structurally sound.
The result is a QA layer built into the modeling environment itself—one you don’t have to design, document, or maintain separately.
Compared to Excel
In Excel, managing units is manual. Cells don’t carry unit metadata, formulas don’t validate unit consistency, and catching a unit error typically requires color-coding columns, adding header rows, or relying on the reviewer to notice a mismatch. In Aire, units are a first-class property of every term. The platform enforces consistency across every formula automatically. You still have to write correct formulas—but you get immediate feedback when units don’t line up, rather than finding out after a presentation or an audit.How Units Flow Through Formulas
Aire tracks units through arithmetic automatically.| Operation | Example | Result |
|---|---|---|
| Same unit | 100 kWh + 50 kWh | 150 kWh |
| Multiply | 100 MW × 8 h | 800 MWh |
| Divide | 500 km ÷ 2 h | 250 km/h |
| Cancel | $50,000/year × 10 years | $500,000 |
| Calendar chain | 16 hours/day × 22 days/month | 352 hours/month |
Calendar Rates
One of the most important distinctions in the unit system is the difference between a calendar rate and a physical rate. Physical rates likeUSD/hr represent a continuous flow—the kind you’d measure with a flow meter or integrate over time. Use physical rates when the quantity is genuinely continuous: heat flux, electrical power, fuel consumption.
Calendar rates like USD/month or MWh/year represent scheduled accounting periods. These are common in financial modeling: a budget is 50,000/monthstays$50,000/month`.
The rule of thumb: if you would write it on a budget spreadsheet, it’s a calendar rate. If you would measure it with an instrument, it’s a physical rate.
Calendar Ratios
Calendar ratio units likehours/day and days/month let you chain calendar-period calculations so periods cancel correctly:
day tokens cancel and you get hours/month. Make sure your calendar chains fully resolve—multiplying days/month by a bare year (instead of months/year) leaves unresolved periods and will raise a unit error.
Unit Conversion with CONVERT()
The CONVERT() function converts a value from one unit to another, as long as both units measure the same quantity.
| Formula | Result |
|---|---|
CONVERT(1, "MWh", "kWh") | 1000 kWh |
CONVERT(100, "km", "mi") | 62.137 mi |
CONVERT(25, "C", "F") | 77 F |
CONVERT(1200, "USD/year", "USD/month") | 100 USD/month |
kWh to kg) will produce an error.
Unit Reference
Units are case-sensitive. Use the exact strings in the “Type in…” column.Energy
| Unit | Type in… | Notes |
|---|---|---|
| Watt-hour | Wh | |
| Kilowatt-hour | kWh | Most common for electricity |
| Megawatt-hour | MWh | |
| Gigawatt-hour | GWh | |
| Terawatt-hour | TWh | |
| British Thermal Unit | BTU or Btu | |
| Million BTU | MMBtu or MMBTU | Common in natural gas |
| Unit | Type in… |
|---|---|
| kWh per year | kWh/year or kWh/yr |
| kWh per month | kWh/month or kWh/mo |
| MWh per year | MWh/year or MWh/yr |
| MWh per day | MWh/day |
| MMBtu per year | MMBtu/year or MMBtu/yr |
Power
| Unit | Type in… | Notes |
|---|---|---|
| Watt | W | |
| Kilowatt | kW | |
| Megawatt | MW | |
| Gigawatt | GW | |
| Megawatt DC | MW-DC | Solar nameplate capacity |
Currency
| Unit | Type in… |
|---|---|
| US Dollar | USD or $ |
| Euro | EUR or € |
| Million USD | USD_M or $M |
| Unit | Type in… |
|---|---|
| USD per year | USD/year or $/year |
| USD per month | USD/month or $/month |
| USD per week | USD/week or $/week |
| USD per day | USD/day or $/day |
| Unit | Type in… |
|---|---|
| USD per kWh | USD/kWh or $/kWh |
| USD per kW | USD/kW or $/kW |
| USD per MWh | USD/MWh or $/MWh |
| USD per kW-year | USD/kWyr or $/kWyr |
| USD per MMBtu | USD/MMBtu or $/MMBtu |
| USD per ton | USD/ton or $/ton |
| USD per kg | USD/kg or $/kg |
| USD per m² | USD/m² or $/m2 |
| USD per acre | USD/acre or $/acre |
| USD per hectare | USD/ha or $/ha |
Mass
| Unit | Type in… | Notes |
|---|---|---|
| Kilogram | kg | |
| Metric ton | t or MT | 1,000 kg |
| Pound (mass) | lbm | |
| CO₂ (metric ton) | tCO2 | Carbon accounting |
| Hydrogen (kg) | kgH2 |
Time
| Unit | Type in… |
|---|---|
| Second | s |
| Minute | min |
| Hour | h |
| Day | day |
| Week | week |
| Month | month |
| Quarter | quarter |
| Year | year |
Temperature
| Unit | Type in… |
|---|---|
| Celsius | C |
| Fahrenheit | F |
| Kelvin | K |
Calendar Ratios
| Unit | Type in… |
|---|---|
| Hours per day | hours/day |
| Days per month | days/month |
| Days per year | days/year |
| Hours per month | hours/month |
| Hours per year | hours/year |
| Months per year | months/year |
| Weeks per month | weeks/month |
| Quarters per year | quarters/year |
Other
| Unit | Type in… | Notes |
|---|---|---|
| Meter | m | |
| Kilometer | km | |
| Square meter | m² | |
| Hectare | ha | 10,000 m² |
| Acre | ac | |
| Cubic meter | m³ | |
| Liter | L | |
| Pascal | Pa | Pressure |
| Volt | V | |
| Ampere | A | |
| Mole | mol | |
| Parts per million | ppm | |
| Percent | % |