Built by energy professionals. Designed for everyone.

Free, no-signup energy calculators—from AI data centers to everyday home energy costs. Every calculation explained. Every source cited.

Data centers are among the fastest-growing electricity consumers in the world — tools for developers, investors, operators, and utilities to estimate demand, infrastructure sizing, operating costs, and sustainability impacts.

One of the fastest-growing sectors in energy and a signature WattThe?! content area — tools for beginners and experienced professionals, residential through utility scale.

For developers and utilities evaluating storage technologies beyond lithium-ion — flow batteries, pumped hydro, compressed air, and thermal storage for multi-day and seasonal duration.

For power plant operators, EPCs, and policymakers evaluating the cost and feasibility of capturing, transporting, and storing CO2 from industrial and power generation facilities.

For homeowners, developers, EPCs, engineers, and investors — technical performance and project economics with irradiance, degradation, and loss assumptions shown.

For homeowners, renters, contractors, electricians, and residential solar installers — practical answers without requiring an engineering background.

For facility managers, business owners, consultants, EPCs, and energy professionals quantifying savings, operational improvements, and resilience.

For consumers, fleet managers, charging network developers, and utilities.

For engineers, project developers, policymakers, and investors exploring emerging hydrogen technologies.

Converting municipal solid waste into firm, dispatchable baseload electricity — the generation technology that gets paid twice, for the fuel and the power.

Wind generation sizing and the economics of pairing variable renewables with firm computing load — co-location, stranded-energy computing, and energy-first data center development.

Resource adequacy and the grid-level math behind how much new load a system can actually absorb — reserve margins, capacity adequacy, and the reliability standards that govern them.

For utilities, developers, and data center operators evaluating nuclear and small modular reactors as firm, carbon-free baseload power.

For developers, engineers, and investors evaluating geothermal resources for utility-scale power and enhanced geothermal systems (EGS) — drilling cost, plant output, and project economics.

Consistent methodologies for evaluating energy investments across technologies and project sizes — LCOE, NPV, IRR, and more, with assumptions, discount rates, and degradation documented.

More calculators in development — view the roadmap →

Units of electricity

Power and energy are different things, and the difference is the key to every calculator on this site: power (watts) is how fast electricity is being used right now, while energy (watt-hours) is how much has been used over time. Utilities bill for energy, so cost is always wattage × hours — never wattage alone.

A watt (W) is the base unit. A kilowatt (kW) is 1,000 watts, and a kilowatt-hour (kWh) is one kilowatt sustained for one hour; it is the billing unit because a typical US home uses ~10 million watt-hours a year — 10,000 kWh reads better.

A megawatt (MW) is 1,000 kilowatts — one million watts — and a megawatt-hour (MWh) is that power sustained for one hour. These are the working units of data center developers and utility-scale energy projects: an AI campus is negotiated in MW of grid capacity, a solar plant is nameplated in MW, and battery storage is bought and sold in MWh.

The BTU (British Thermal Unit) measures heat: 1 kWh equals 3,412 BTU. It's how an air conditioner's rating connects to its electrical draw, and how a data center's IT load becomes a cooling problem.

Horsepower is 745.7 W (mechanical) or 735.5 W (metric), thanks to James Watt, who invented the unit to sell steam engines against draft horses — rounded, one horsepower is 746 watts.

And the ton of cooling — 12,000 BTU per hour — is sized for everything from a home AC to a data center chiller plant. One ton of cooling typically requires about 1–1.2 kW of electricity.

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