20-Year Planning Horizons: Engineering for 2045 Today

How do you design for load growth you can't predict 20 years out? The answer is changing everything about transmission planning

When ISO New England's planners sat down to develop their first 20-year transmission plan under FERC Order 1920, they faced a seemingly impossible challenge: design infrastructure for 2045 when they couldn't confidently predict load growth for 2027. Their solution required abandoning decades of traditional forecasting approaches and embracing radical uncertainty as a design constraint rather than a planning failure.

The result was a $15 billion transmission portfolio that performs well under scenarios ranging from massive data center deployment to widespread electrification to economic recession—using flexible design principles and adaptive strategies that would have been considered engineering heresy just five years ago. More importantly, it demonstrated that uncertainty isn't a problem to be solved but a reality to be engineered around.

Yesterday we explored the seven benefit categories that must be evaluated for every transmission project. Today, let's examine how those benefits must be calculated across 20-year planning horizons using scenario-based methodologies that fundamentally change how we approach long-term infrastructure design.

The Death of Traditional Load Forecasting

How We Used to Plan

Traditional 10-15 Year Forecasting:

• Historical Extrapolation: Linear regression based on past load growth

• Economic Correlation: Load growth tied to GDP and population projections

• Single Point Forecasts: Most likely future with sensitivity analysis

• Gradual Change Assumption: Evolutionary rather than revolutionary load development

Example Traditional Forecast:

Annual Load Growth = 1.5% ± 0.5%
2035 Peak Load = 2025 Peak × (1.015)^10 = 116% of current
Planning Margin = 15% reserve margin
Required Capacity = 116% × 1.15 = 133% of current capacity

Why 20-Year Horizons Break Traditional Models

Exponential Uncertainty: Forecast accuracy degrades exponentially with time horizon:

• Year 3: ±5-10% accuracy typical

• Year 10: ±15-25% accuracy achievable

• Year 20: ±50-100% uncertainty common

• Unprecedented Changes: New technologies and policies create discontinuities

Multiple Disruption Potential: 20-year horizons encompass multiple technology and policy cycles:

• Data Center Explosion: 4% to 15% of grid consumption

• Transportation Electrification: 20-40% vehicle electrification by 2045

• Industrial Electrification: Heat pumps, electric steel, hydrogen production

• Distributed Energy Resources: Rooftop solar, batteries, microgrids

• Climate Policy: Carbon pricing, renewable mandates, fossil fuel restrictions

Scenario-Based Planning Methodology

Constructing Robust Scenarios

Order 1920 Requirement: Multiple scenarios reflecting different possible futures Best Practice: 4-6 scenarios covering diverse but plausible outcomes

Core Scenario Framework:

1. Reference Case: Current trends continue with modest evolution

2. High Electrification: Aggressive transportation and heating electrification

3. High Renewables: Rapid clean energy deployment with storage

4. Data Center Boom: Hyperscale data center development accelerates

5. Economic Disruption: Recession, supply chain issues, or other shocks

6. Climate Action: Comprehensive carbon pricing and policy implementation

Reference Case Scenario Development

Load Growth Drivers:

• Population Growth: Regional demographic projections

• Economic Development: GDP growth and industrial expansion

• Energy Efficiency: Building codes and appliance standards

• Distributed Generation: Rooftop solar and storage adoption

• Current Policy: Existing renewable portfolio standards and regulations

Key Assumptions:

• 2-3% annual load growth through 2035, slowing to 1-2% through 2045

• 30-40% renewable penetration by 2045

• Limited transportation electrification (<20% vehicle sales)

• Moderate data center growth (8-10% of total consumption)

• Evolutionary rather than revolutionary technology deployment

High Electrification Scenario

Transportation Transformation:

• Electric Vehicle Adoption: 60-80% of vehicle sales by 2035

• Heavy-Duty Electrification: Buses, trucks, freight electrification

• Charging Infrastructure: Massive charging network deployment

• Load Impact: 15-25% increase in total electricity consumption

Building Electrification:

• Heat Pump Deployment: 50-70% of heating systems electrified

• Industrial Process Heat: Electric boilers, heat pumps for manufacturing

• Peak Load Impact: Winter heating peaks rival summer cooling peaks

• Grid Implications: Seasonal load patterns fundamentally change

Load Characteristics:

2045 Peak Load = 2025 Peak × 1.6-1.8
Winter Peak = Summer Peak (vs. traditional summer-dominant)
Transportation Load = 20-25% of total consumption
Building Electrification = 15-20% load increase

High Renewables Scenario

Generation Mix Transformation:

• Solar Deployment: 200-400 GW additional solar by 2045

• Wind Expansion: 150-300 GW additional wind capacity

• Storage Requirements: 100-200 GW of battery storage

• Transmission Needs: Massive transmission expansion for renewable delivery

Grid Operations Impact: