---
title: "Intermittency — AP Environmental Science Definition"
description: "Intermittency is the on-and-off nature of renewables like solar and wind due to weather, time of day, or season. Key to Unit 6 energy tradeoff questions."
canonical: "https://fiveable.me/ap-enviro/key-terms/intermittency"
type: "key-term"
subject: "AP Environmental Science"
unit: "Unit 6"
---

# Intermittency — AP Environmental Science Definition

## Definition

In AP Environmental Science, intermittency is the inconsistent power output of renewable energy sources like solar and wind, caused by weather, time of day, or season. It's the main reliability drawback you cite when comparing renewables to nonrenewables in Unit 6 (Topic 6.1).

## What It Is

Intermittency means a [renewable energy](/ap-enviro/key-terms/renewable-energy "fv-autolink") source doesn't produce power constantly. Solar panels generate nothing at night and less on cloudy days. Wind turbines sit still when the air is calm. The fuel is free and naturally replenished, but it shows up on nature's schedule, not yours.

This matters because [electricity](/ap-enviro/unit-6/hydrogen-fuel-cell/study-guide/VBHYpOxkIwXQuPkI6px8 "fv-autolink") demand doesn't pause when the sun sets. The grid needs power every second, so intermittent [sources](/ap-enviro/unit-1/hydrologic-cycle/study-guide/Mnp6Jfh7MANP2YtOhxCb "fv-autolink") have to be paired with something that fills the gaps, like battery storage, hydroelectric power, or a fossil fuel plant that can ramp up quickly. On the AP exam, intermittency is the go-to disadvantage of solar and wind, the same way pollution and finite supply are the go-to disadvantages of fossil fuels. Knowing both sides of that tradeoff is exactly what Topic 6.1 asks of you.

## Why It Matters

Intermittency lives in [Unit 6](/ap-enviro/unit-6 "fv-autolink") (Energy Resources and Consumption) under Topic 6.1, supporting learning objective [AP Enviro](/ap-enviro "fv-autolink") 6.1.A: identifying differences between nonrenewable and renewable energy sources. The CED defines renewables as sources replenished naturally at or near the rate of consumption (EK ENG-3.A.2), but replenishable doesn't mean constant. Intermittency is the catch. It explains why countries can't just flip a switch to 100% solar and wind, and it's the standard counterargument you'll need when an FRQ asks you to evaluate a proposal to switch energy sources. Any time the exam asks for a drawback of solar or wind, intermittency should be the first word in your head.

## Connections

### Renewable vs. Nonrenewable Energy Sources (Unit 6)

Intermittency is one of the sharpest dividing lines in [Topic 6.1](/ap-enviro/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE "fv-autolink"). Fossil fuels are finite but dispatchable, meaning you can burn them whenever demand spikes. Solar and wind are infinite but intermittent. Almost every energy comparison question on the exam comes down to that tradeoff.

### [Natural Gas (Unit 6)](/ap-enviro/key-terms/natural-gas)

[Natural gas](/ap-enviro/key-terms/natural-gas "fv-autolink") plants can ramp up and down quickly, so grids often use them to cover the gaps when solar and wind output drops. That's why a renewable-heavy grid can still depend on fossil fuels, a nuance that makes for a strong FRQ point.

### Hydroelectric Power and Energy Storage (Unit 6)

[Dams](/ap-enviro/key-terms/dams "fv-autolink") and pumped storage act like giant batteries, releasing water to generate power when intermittent sources go quiet. If an FRQ asks how to solve intermittency, storage is your answer.

### Solar Insolation and Seasons (Unit 4)

Unit 4 explains the physics behind intermittency. The angle of the sun, seasonal changes, and weather patterns all control how much solar energy actually reaches a panel. Connecting the two units shows the kind of cross-topic reasoning AP readers reward.

## On the AP Exam

Intermittency shows up most often in multiple-choice stems asking you to identify a disadvantage of solar or wind energy, or to explain why a region still relies on fossil fuels despite adding renewables. Practice questions also fold it into energy economics, like asking what assumptions underlie an argument about energy markets (an argument for renewables often quietly assumes the intermittency problem gets solved by storage or backup sources). On FRQs, use it two ways. First, as a drawback when you're asked to describe disadvantages of a renewable source. Second, as the reason behind a solution when you propose battery storage, pumped hydro, or a diversified energy mix. Don't just name it. Explain the mechanism, such as 'solar output drops to zero at night, so the grid needs storage or backup generation to meet demand.'

## intermittency vs Nonrenewability

Intermittent does not mean nonrenewable. A nonrenewable source like oil exists in a fixed amount and runs out (EK ENG-3.A.1). An intermittent source like solar never runs out, it just pauses. Sunlight replenishes every single day, which makes it fully renewable under EK ENG-3.A.2. Intermittency is about timing of supply, not total supply. Mixing these up is one of the easiest ways to lose points on a Unit 6 question.

## Key Takeaways

- Intermittency is the inconsistent power output of renewable sources like solar and wind, caused by weather, time of day, and seasonal changes.
- An intermittent source is still renewable because the energy replenishes naturally; intermittency is about when power is available, not whether it runs out.
- Intermittency is the standard disadvantage to cite for solar and wind on the AP exam, just like pollution is the standard disadvantage for fossil fuels.
- Grids handle intermittency with battery storage, pumped hydroelectric power, or dispatchable backup plants like natural gas.
- Fossil fuels and nuclear are not intermittent, which is a major reason they still dominate baseload power generation despite their environmental costs.

## FAQs

### What is intermittency in AP Environmental Science?

Intermittency is the variability in power output from renewable sources like solar and wind, caused by weather, time of day, or season. It's tested in Unit 6 (Topic 6.1) as a key disadvantage of renewables compared to fossil fuels.

### Does intermittency mean solar and wind are nonrenewable?

No. Solar and wind are fully renewable because they replenish naturally at or near the rate of consumption (EK ENG-3.A.2). Intermittency just means the power output isn't constant, not that the source will run out.

### How is intermittency different from a fuel shortage?

A fuel shortage means a nonrenewable resource like oil is being depleted and there's physically less of it. Intermittency means the resource (sunlight, wind) is unlimited overall but unavailable at certain times, like solar at night. One is a supply problem, the other is a timing problem.

### How do we solve the intermittency problem?

The main solutions are energy storage (batteries, pumped hydroelectric storage), backup dispatchable plants like natural gas, and a diversified mix of energy sources across a region. FRQs love asking you to propose one of these with an explanation of how it fills the gap.

### Which energy sources are intermittent on the AP Enviro exam?

Solar and wind are the classic intermittent sources. Hydroelectric, geothermal, and biomass are renewable but much more consistent, and fossil fuels and nuclear are not intermittent at all. Knowing which renewables are intermittent and which aren't is an easy MCQ win.

## Related Study Guides

- [6.1 Renewable and Nonrenewable Resources](/ap-enviro/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE)

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