WattTime

Free

WattTime is a nonprofit that gives you data to time your electricity use when the grid is cleanest. It works with smart devices, electric vehicles, and energy procurement teams.

WattTime sits in Data & Analytics. It tracks real-time grid emissions across 200+ countries and sends signals to shift your power use to cleaner windows.

You do not use it directly. Device makers, apps, and energy teams plug into its API. Your charger or thermostat does the work in the background.

It is free. The nonprofit model means they want the idea to spread, not lock you in.

Open it if you buy clean energy or build devices that use power. Skip it if you want a consumer app with a dashboard.

It helps when you need location-specific emissions data or flexible load timing.

• Large organizations making renewable energy procurement decisions: You see which projects cut real emissions. Boston University used it to pick South Dakota wind and cut carbon 53%.
• Sustainability teams needing location-specific emission impact analysis: You compare projects by what they actually displace, not just their headline capacity.
• Universities with net-zero targets seeking maximum leverage from clean energy investments: Your procurement delivers 2–3× more avoided emissions by picking the right grid.
• EV owners with flexible charging schedules: Your car charges when the grid runs on wind or solar, not coal.
• Smart home users with programmable thermostats: Your devices shift automatically without you changing behavior.
• Electric vehicle fleet operators seeking emissions optimization: You cut fleet charging emissions without buying new hardware.
• Smart device manufacturers wanting to add environmental features: You add carbon-aware timing with a few lines of code.
• Renewable energy developers optimizing project siting: You prove your project displaces dirty power, not clean power already on the grid.
• Data center operators and owners: You schedule AI training or batch jobs for the cleanest hours.
• Corporations needing defensible Scope 2 emissions accounting: Your reports use hourly marginal emissions data, not annual averages.

These are the parts that matter after you start using it.

• Real marginal emissions data: It tells you which power plant your next kilowatt would actually come from. You avoid the trap of "green" energy that displaces other renewables.
• Hourly granularity: You see five-minute to hourly shifts in grid mix. In California, one-third of hours have near-zero carbon intensity while others fire up gas plants.
• Automated shifting without behavior change: Your devices move demand silently. You do not need to think about when to plug in.
• Nonprofit alignment: They help competitors copy the feature. You get support without vendor lock-in.
• Major partner validation: Google Nest, Honda, and Toyota already use it. You are not testing unproven tech.

It is not the right fit for every situation.

• Skip it if you need a consumer dashboard: There is no app to open. You get API access or work through partner devices.
• Skip it if your load is fixed: It only helps with flexible demand. A factory running 24/7 cannot shift much.
• Skip it if your grid is always dirty or always clean: The benefit comes from variability. Some regions have flat emissions all day.
• Skip it if you need guaranteed savings proof: Most effectiveness claims come from WattTime itself. Independent verification is thin.
• Skip it if you need fast enterprise support: Volunteer-dependent development means response times can lag.