Shifts, Shortages, and Surpluses

Heat waves move curves; retirements move stacks

August 2025: temperatures hit 104°F, air conditioners hummed, and ClearPeak set a new peak at 8,620 MW. The same month, a coal unit tripped offline for maintenance. Demand shifted right while supply shifted left. Tom fielded media calls about "price gouging" when wholesale prices hit $0.28/kWh. Elena replied with vocabulary: simultaneous demand shift and supply shift, producing a shortage relative to prior equilibrium.

ClearPeak Energy is a regulated regional electric utility serving 1.2 million residential and commercial customers across twelve counties and the anchor organization for ECO 101. The utility faces retiring 2,400 MW of coal while adding 1,800 MW of utility-scale solar and battery storage by 2030, peak summer demand near 8,500 MW, and an average residential bundled rate of $0.118/kWh (kilowatt-hour, enough electricity to run ten 100-watt bulbs for one hour). Chief Economist Dr. Elena Vasquez, Regulatory Affairs VP Tom Bradley, and Grid Planning Director Amara Okafor use microeconomic tools for rate design, capacity planning, competitive response, and State Public Utilities Commission (PUC) testimony. Marginal generation costs differ sharply: legacy coal near $0.042/kWh, new solar near $0.031/kWh, and gas peakers near $0.067/kWh when scarcity bites.

Every lesson applies supply, demand, elasticity, marginal analysis, market structure, or incentive design to decisions ClearPeak leaders actually face: when to retire plants, how to price time-of-use tiers, how to bid in capacity auctions, and how to respond when rooftop solar erodes sales.

Demand shifts: causes and directions

Demand increases (shifts right) when income rises, population grows, complements cheaper, or preferences favor electricity (EVs). Demand decreases (shifts left) when substitutes like rooftop solar improve or efficiency standards tighten.

Graph (described in prose): Heat wave demand shift. Imagine a standard microeconomics diagram with quantity (MW) on the horizontal axis and wholesale price ($/kWh) on the vertical axis. Original demand D0 intersects supply at 8,100 MW and $0.08/kWh. Short-run supply stack S0 fixed for the day. Initial equilibrium point E0. Heat wave shifts demand right to D1; new equilibrium E1 at higher price and quantity unless supply also shifts.

Supply shifts: causes and directions

Supply shifts right when new solar comes online or fuel costs fall. Supply shifts left when coal retires, gas prices spike, or plants trip offline. ClearPeak's 2,400 MW coal retirement is a planned leftward shift over five years.

Shortages and surpluses when prices are flexible

If price is stuck below clearing level, quantity demanded exceeds quantity supplied: shortage. Above clearing, surplus. With flexible wholesale prices, shortages show as price spikes; with frozen retail, as load shed risk.

Simultaneous shifts

Net effect depends on magnitudes. Heat wave (demand right) plus coal outage (supply left) unambiguously raises price. Solar build (supply right) plus EV adoption (demand right) has ambiguous price effect: quantity rises, price change depends on relative shift sizes.

Policy responses

Shortage responses: demand response, imports, temporary peakers, TOU price spikes, public appeals. Surplus responses: export power, curtail renewables (economic surplus waste). Amara hates renewable curtailment; batteries absorb surplus.

Baseline peak 8,100 MW at $0.08/kWh wholesale. Events: heat wave +600 MW demand; coal outage -400 MW supply.

Part A: Direction

Demand shift right +600 MW at each price. Supply shift left -400 MW at each price. Net need +1,000 MW at old price → shortage pressure.

Part B: Price outcome

Clearing price rose to $0.28/kWh for two hours; gas peakers set margin. Consumer surplus fell; producer surplus rose on inframarginal units.

Part C: Regulatory narrative

Tom's talking points: (1) price signal reflected scarcity, (2) revenue cap means surplus may be shared via fuel adjustment clauses, (3) long-run fix is supply shift right via batteries.

Part D: Managerial read

Accelerate battery procurement when simultaneous shift events produce repeated price spikes above $0.20/kWh.

European markets sometimes curtail wind surplus at negative prices. ClearPeak plans storage to avoid wasting solar surplus during spring afternoons.

Baseline equilibrium: Q*=8,000 MW at P*=$0.10/kWh. Heat wave increases quantity demanded by 500 MW at every price. Coal outage reduces quantity supplied by 300 MW at every price. Describe new shortage/surplus at P=$0.10. Qualitatively predict price direction.

Solution

At unchanged P=$0.10, Qd = 8,500 MW, Qs = 7,700 MW → shortage 800 MW. Flexible prices must rise to clear market. Check: 500 MW demand increase + 300 MW supply decrease = 800 MW gap ✓

Key takeaways

• Shifts move entire curves; movements trace price changes along a curve.
• ClearPeak faces demand right trends (EVs) and supply left shocks (coal retirement).
• Shortages with flexible prices show as spikes; with rigid retail, as reliability risk.
• Simultaneous shifts require comparing magnitudes, not single-cause stories.
• Surplus hours need storage or export to avoid curtailment waste.

1. Write one demand shift and one supply shift affecting ClearPeak this decade.
2. Explain Tom's media answer without blaming 'gouging' vocabulary.
3. Continue to Unit 2 Lesson 1: Price Elasticity of Demand.

Applying Shifts, Shortages, and Surpluses at ClearPeak scale

When ClearPeak Energy evaluates shifts, shortages, and surpluses, Dr. Elena Vasquez starts from operational facts: 1,200,000 customers, peak demand near 8,500 MW, residential bundled rate $0.118/kWh, and a portfolio transition that retires 2,400 MW of coal while adding 1,800 MW of solar. supply, demand, equilibrium, and market adjustments is not textbook decoration; it is how Tom Bradley prepares State Public Utilities Commission (PUC) filings and how Amara Okafor ranks transmission and storage options under binding capital budgets.

Graph (described in prose): Shifts, Shortages, and Surpluses at ClearPeak. Imagine a standard microeconomics diagram with quantity (megawatt-hours or customer count, depending on the decision) on the horizontal axis and price ($/kWh) or marginal cost ($/kWh) on the vertical axis. The demand curve slopes downward: at higher retail rates, customers conserve, shift load to off-peak hours, or install rooftop solar. The supply curve in the short run reflects rising marginal cost as ClearPeak dispatches coal, combined-cycle gas, and expensive peakers. Equilibrium is where quantity demanded equals quantity supplied at a price regulators allow; in regulated markets, equilibrium is a negotiated outcome, not only a frictionless auction. When ${title.toLowerCase()} changes, curves shift: new solar lowers long-run supply cost; heat waves shift demand right; competitor solar leases shift demand left for utility energy. Shaded consumer surplus and producer surplus (or deadweight loss when prices depart from marginal cost) translate directly into affordability testimony and earnings impacts.

Work a magnitude check. Suppose a policy tied to shifts, shortages, and surpluses moves residential sales by 1% at current scale. One percent of 1,200,000 customers is 12,000 accounts. At roughly 900 kWh per month average use and $0.118/kWh, a 1% quantity change moves monthly revenue by about $1.3 million before fuel cost adjustments. Executives who skip arithmetic like this debate symbols without stakes.

Extended ClearPeak scenario: regulatory and competitive read

Imagine ClearPeak's quarterly review on shifts, shortages, and surpluses. Finance asks whether a rate increase recovers rising gas peaker costs. Operations asks whether demand response can defer a $400 million substation upgrade. Commercial customers ask for advanced metering discounts. Rooftop solar installers tell regulators ClearPeak exercises market power. A weak supply, demand, equilibrium, and market adjustments answer addresses only one audience. A strong answer links curves, elasticities, and marginal costs to each stakeholder's metric.

Dr. Vasquez uses a three-panel narrative. Panel one: short-run dispatch when peak load hits 8,500 MW and peakers set marginal cost near $0.067/kWh. Panel two: long-run portfolio when solar at $0.031/kWh displaces coal at $0.042/kWh plus carbon compliance. Panel three: competitive fringe where distributed solar at $0.09/kWh effective price steals high-margin afternoon sales. Shifts, Shortages, and Surpluses supplies vocabulary to keep the panels consistent.

Numerical discipline example: if price elasticity of residential demand is -0.35 (a 1% price rise cuts quantity about 0.35%), a 4% rate increase reduces energy sales roughly 1.4% in the short run. Combined with weather normalization, Elena reports a bounded revenue forecast instead of pretending demand is fixed. Regulators punish utilities that ignore elasticity in revenue requirement testimony.

Technical mechanics and reconciliation checks

For shifts, shortages, and surpluses, ClearPeak analysts show work the way accountants show trial balances. A supply table lists plant, capacity MW, heat rate, variable O&M, fuel cost, and marginal cost per MWh (megawatt-hour). A demand table lists customer class, price, quantity, and expenditure. Equilibrium checks that quantity demanded equals scheduled dispatch within reserve margin rules. Elasticity checks recompute percent changes with the same denominator conventions used in the tariff filing.

Use explicit formula lines before plugging numbers. Elasticity = percent change in quantity demanded divided by percent change in price. Marginal cost = change in total cost divided by change in output. Marginal revenue = change in total revenue divided by change in quantity sold. Consumer surplus approximates the area below demand and above price for the units consumed. When lessons use linear demand shortcuts, state the assumption: "linear between two observed tariff points."

Spreadsheet grain matters. Utility models often run hourly for dispatch, monthly for billing, and annual for regulatory revenue requirements. Shifts, Shortages, and Surpluses fails silently when rows mix grains. Elena requires a grain column in every workbook: hour, month, customer-month, or plant-year.

Common executive questions (and disciplined answers)

Executives ask short questions that need long disciplined answers. "Can we pass fuel costs through?" maps to allowed riders, elasticity, and affordability indices, not anger on social media. "Will solar kill the utility?" maps to cross-price elasticity with distributed energy and fixed cost recovery. "Why not cut rates to grow?" maps to marginal revenue sign when |elasticity| < 1. "What is fair return?" maps to allowed revenue requirement and cost of capital, not last year's earnings plus 10%.

ClearPeak's credible answer format for shifts, shortages, and surpluses is three bullets: recommendation, key elasticities or marginal costs behind it, and what evidence would reverse the view within two quarters. A fourth bullet names deadweight loss or equity tradeoffs when policy moves price away from marginal cost.

Practice the translation loop until habit: business question → curves and elasticities → quantity and revenue arithmetic → stakeholder table → filing language. Broken loops produce pretty charts that fail cross-examination.

Practice extension: graph and arithmetic self-check

Before re-reading solutions, sketch four items on paper. Item one: draw (in words) demand and supply for ClearPeak summer peak hours with labels. Item two: write one shift that increases price and one that decreases quantity without a price change. Item three: compute percent ΔQ and percent ΔP for a scenario in the lesson and verify elasticity sign. Item four: state who gains and who loses in surplus terms.

Compare your sketch to the worked example. Gaps tell you what to re-read. If you work outside utilities, substitute your product but keep the same structure: define market, state margins, show equilibrium, stress-test with elasticity.

Connection to ACC 101, MKT 202, and capstone design

ACC 101 taught you to reconcile statements; ECO 101 teaches you to reconcile marginal stories with average costs regulators allow. MKT 202 taught evidence ladders; here the ladder is descriptive load research → elasticity estimation → pricing experiment or pilot tariff → regulatory approval. Unit six capstone on designing incentives expects you to combine supply, demand, equilibrium, and market adjustments with game theory and externality tools from earlier units.

Integrated narrative example: ClearPeak proposes a peak-pricing pilot (MKT-style segmentation), estimates elasticity −0.35 (ECO 101 Unit 2), models revenue with marginal cost dispatch (Unit 3), and defends fairness to the PUC (Unit 6). Courses compound when vocabulary and numbers stay consistent.

Deep dive: ClearPeak data definitions reused every month

Residential bundled rate includes energy, distribution, and mandated riders; pilots may unbundle for time-of-use. Peak demand is the highest hourly load in a month; coincident peak may determine transmission charges. Marginal cost of service for pricing studies uses forward-looking dispatch, not historical average embedded cost. Lost revenue from energy efficiency or solar is offset by decoupling mechanisms in some filings. Elasticity estimates separate weather, price, income, and appliance stock effects.

Definition drift fakes wins. If operations reports peak MW using one weather adjustment and finance uses another, shifts, shortages, and surpluses recommendations flip. Elena publishes a one-page data dictionary before each major filing.

Monthly reconciliation: billed energy ≈ generation net losses ± inventory; revenue ≈ Σ quantity × tariff by class; marginal cost tables sum to dispatch cost within rounding. Elasticity replays on holdout months. When reconciliations fail, fix data before arguing policy.

Managerial judgment prompts for Shifts, Shortages, and Surpluses

1. If elasticity is inelastic short run but elastic long run, how should ClearPeak sequence a multi-year rate path?
2. If marginal solar cost is below coal but fixed grid costs rise, is average cost or marginal cost the right public narrative?
3. Which stakeholder loses most if ClearPeak underestimates cross-price elasticity with rooftop solar?
4. What observable would convince you the demand curve shifted versus movement along the curve?
5. When does surplus language help regulators and when does it sound like economist jargon?

Write ninety-word memo answers using ClearPeak numbers. This converts lesson prose into testimony reflexes.

Additional study path: compare this lesson's practice problem to the worked example. Identify one assumption that changed elasticity or marginal cost and explain how the decision flips. Capstone integration is intentional; reuse ClearPeak names and units across units.

Numerical walk-through: peak hour dispatch

Consider a summer peak hour with 8,500 MW demand. ClearPeak dispatches 3,200 MW coal at $0.042/kWh variable, 3,800 MW combined-cycle gas at $0.055/kWh, 800 MW solar at near-zero variable cost, and 700 MW peakers at $0.067/kWh. The marginal unit sets price in competitive benchmarks; in regulation, the filing may use average revenue requirement. Weighted average variable cost ≈ (3200×0.042 + 3800×0.055 + 800×0.005 + 700×0.067) / 8500 ≈ $0.046/kWh before T&D (transmission and distribution).

If shifts, shortages, and surpluses motivates shifting 200 MW from peak to off-peak via time-of-use pricing, peaker runs drop, variable cost falls roughly 200×$0.067 = $13,400 per hour, plus avoided capacity charges if sustained. Demand response programs trade customer incentives against this savings. Elena documents both gross savings and participation costs; net benefit drives the filing.

Check: 3200+3800+800+700 = 8500 MW ✓. Any lesson using partial portfolios should show similar capacity checks.

Surplus, equity, and policy tradeoffs

Microeconomics is not only efficiency. Shifts, Shortages, and Surpluses at ClearPeak intersects affordability programs for low-income households, equity when time-of-use shifts burden evening home use, and environmental justice when retired coal plants sit in vulnerable communities. Consumer surplus gains for average bills may hide losses for heat-vulnerable customers.

When lessons recommend raising price toward marginal cost, pair the recommendation with a transfer or assistance mechanism or explain why the PUC weights equity constraints. Dr. Vasquez tables deadweight loss of under-pricing peak energy alongside hardship metrics. Regulators accept tradeoffs stated clearly; they reject efficiency claims that ignore distributional facts.

For supply, demand, equilibrium, and market adjustments, practice writing one paragraph that a non-economist commissioner could read aloud. Avoid surplus jargon without translation: "customers who value afternoon cooling less than the cost of peaker plants would consume less under peak pricing, freeing capacity for hospitals and industrial employers."