What are Injection and Withdrawal Capacity Heat Maps?
Paces Injection and Withdrawal Heat Maps visualize estimated injection (power export) and withdrawal (power import) capacity for a transmission bus or tap. They help infrastructure developers understand how much additional power the grid can absorb or deliver at specific substations.
These are especially valuable for the following development types:
Data Centers – checking if a site can support large import/off-take loads
Battery Energy Storage Systems (BESS) – checking if a site can support large import/off-take loads
Utility-scale Solar/Wind – checking if a site can support off-take loads
Methodology
How does Paces produce these heat maps?
In order to produce heat maps, Paces maps busses and taps to substations, per utility. Once matched, Paces runs power flow simulations using CEII base cases (typically 2028 or 2030 Summer Peak) from utilities and ISOs. These base cases represent modeled grid conditions, and each simulation incorporates:
N-1 contingency conditions (assumes one grid element failure)
Each heat map corresponds to a planning case, which includes:
A specific year + season (ex: 2028 Summer Peak)
System topology
Load/generation forecasts
Interconnection queue assumptions
Some cases assume all queued projects will be built (conservative), others only include signed agreements (optimistic).
Important Definitions
Case: A digital model of the transmission grid at a certain point in time. It includes grid layout, load, generation, and constraints.
Summer Peak: The period of highest electricity demand in summer - used to test grid stress under extreme conditions.
Contingencies: Simulate "what-if" failures, like a transformer outage or generator trip. We follow N-1 contingency conditions:
Remove one element (line, transformer, generator)
Recalculate power flows
Test thermal limits
Record the safe capacity at each bus
💡 Because Paces include worst-case checks in our heat maps, our numbers reflect realistic, N-1 conditions.
Which tools does Paces use to produce the maps?
We use TARA's Advanced Transfer Limit Analysis (Advanced TrLim):
Transfer Limit Evaluation – calculates how much generation a bus can handle (injection)
Load Hosting Analysis – measures how much additional load can be supported (withdrawal)
How often are the maps updated?
We refresh heat maps when new planning cases are released by utility or ISO. Each region has its own cadence (annual, semi-annual, or quarterly).
What sets Paces' heat maps apart from other maps?
⭐ 1. AC-based modeling rather than DC approximations
Most platforms rely on DC (Direct Current) methods, which simplify grid behavior and can miss key operational constraints. Paces uses AC (Alternating Current) modeling, giving a more accurate representation of real power flows and capturing limitations DC models cannot.
⭐ 2. Visibility into existing overloads
Paces flags nodes where any additional withdrawal would aggravate existing grid constraints, which helps developers identify high-risk POIs early and understand where upgrades or constraints may already be in play.
3. ⭐ Convergence issue detection
We detect and flag non-convergent nodes, something most other platforms don't expose. Convergence issues signal unstable or uncertain conditions. When they appear, we guide users toward Power Flow Studies to determine true capacity and feasibility.
🔥 Heat map analysis is run with conservative assumptions to reflect realistic limits. However, heat maps do not reflect all system conditions and are most useful for high level level analysis when prioritizing sites and comparing capacity across locations.
🧠 For a deeper understanding of interconnection feasibility, we recommend requesting further services Power Flow Analyses.
Using Withdrawal and Injection Heat Maps in Paces
How are the maps delivered in Paces?
We publish each utility/ISO as a private custom dataset so users can:
Find substations or taps with the most available capacity
View substations on map, with infrastructure overlays
View site lists to filter and triage top sites
Heat Map Term Glossary
Field | Description |
Min/Max Voltage (kV) | Standard line-to-line voltage levels evaluated for this grid asset. |
Owner / Operator | Utility responsible for owning and operating the grid asset. |
Min Withdrawal Capacity (MW) | Estimated amount of load that can be added at the lowest modeled bus voltage. |
Max Withdrawal Capacity (MW)* | Estimated amount of load that can be added at the highest modeled bus voltage. This value drives the heat map color for this POI. |
AC Convergence Issues | If TRUE, an AC power flow solution could not converge, so results are based on a DC approximation. Values should be validated with a full power flow study. |
Transfer Worsens Existing Overloads | If TRUE, available capacity is already constrained and indicates that adding new load would increase or worsen existing system overloads. |
Heat Maps in Paces: Map
Map-based heat map exploration helps users:
Quickly identify high-capacity substations across a region
Compare multiple planning cases side-by-side
Spot the best locations near sites already in your portfolio
Layer in infrastructure data, like transmission lines and taps
