Home Energy Efficiency Calculator

Compare billed annual electricity intensity with a scenario you enter.

Inputs and method

Each intensity is annual kWh ÷ conditioned ft². Arithmetic difference = (billed kWh − scenario kWh) ÷ billed kWh × 100.

All empirical factors, rates, percentages, clearances, product yields, and model values shown as inputs are scenario values supplied by you. Their source or measurement basis appears beside the inputs and result. Units remain visible, calculations use unrounded values, and rounding occurs only for display or a whole-package ceiling.

Interpreting the result

This is not an ENERGY STAR score, efficiency diagnosis, audit, forecast, or promised saving.

Treat scenario ranges as sensitivity ranges, not confidence intervals. Check the factor’s version, geography, population or product, system boundary, and date before using the result. A finite arithmetic result does not establish code compliance, certification, safety, forecast accuracy, or model validity.

Validation and rounding

The calculator rejects blank required factors, invalid numeric values, prohibited negatives, impossible relationships, and unsupported modes. No malformed value silently selects another branch. Continuous outputs use the precision displayed in the result; package quantities round up only after waste is applied.

Worked example

12,000 kWh over 1,500 ft² is 8.00 kWh/ft²-year; 10,000 kWh is 6.67. The arithmetic difference is 16.7%; equal use gives 0.0%, and higher comparison use gives a negative difference.

Frequently asked question

Is the percentage a promised saving? No. It is an arithmetic comparison between two entered annual-use scenarios.

Sources

ENERGY STAR, “Save at Home” — current web edition; home-energy overview, accessed 2026-07-09. Route-specific boundary: context and terminology only; it does not supply an entered coefficient, uncertainty, recommendation, or approval.
ENERGY STAR, “Learn About LED Lighting” — current web edition; lighting overview, accessed 2026-07-09. Route-specific boundary: context and terminology only; it does not supply an entered coefficient, uncertainty, recommendation, or approval.
U.S. DOE, “Energy Saver Guide” — 2022 edition; home-energy and solar sections, accessed 2026-07-09. Route-specific boundary: context and terminology only; it does not supply an entered coefficient, uncertainty, recommendation, or approval.