Mepsy: The Appliance & Equipment Climate Impact Calculator

Mepsy is CLASP's digital tool to model the impacts of energy and carbon reduction policies. Pre-loaded with data from 162 countries, it supports analysis and prioritization for the most energy-intensive appliances and equipment.

Launch Mepsy

Analyze efficiency policy options for space heating equipment, ACs, residential water heaters, refrigerators, motors, lighting, fans, televisions

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For efficiency policy practitioners, accurate data and predictive models provide insight into how policy decisions translate to real-world impacts

Setting policies and achieving their benefits requires accurate, actionable data. Mepsy’s dynamic, user-friendly interface guides researchers and policymakers in identifying efficiency policy opportunities and analyzing their energy and carbon impacts.

  • Choose a country or region, product, and expected effective date to calculate policy benefits through 2050
  • Use pre-loaded data from CLASP research and other sources, or enter your own data
  • Download calculation results as a CSV file for further use

Mepsy calculates product energy use according to a “bottom-up” accounting approach which factors in the number of appliances in use in a country, the energy performance of representative products, the climate-intensity of the local power grid, and other variables to analyze the electricity use, carbon dioxide emissions, and consumer energy costs associated with a given policy scenario.

The tool supports policy analysis for space heating equipment, air conditioners, refrigerators, fans, motors, televisions, lighting, and residential water heaters. Coming soon: commercial refrigeration, distribution transformers, and refrigerated display cases.

Explore global and national policy scenarios

Compare major global carbon emitters or select a country for regional analysis to explore a range of business-as-usual and efficiency policy scenarios for energy use, carbon dioxide emissions, and the number of appliances in use

See the CO₂ reductions, energy use, and number of appliances in use under business-as-usual or efficiency policy scenarios

Select a country to project the results of efficiency policy choices there and compare it with other countries in the region. Explore at the country level using the map interface, or dive deeper in the data for a single country.

Mepsy input view interface

Use pre-loaded data or input your own

The Mepsy model is based on a bottom-up stock accounting method that incorporates country-specific data on appliance energy use, markets, economic indicators and other policy factors

Data for Mepsy is drawn from several market research firms and other public and private data sources

Wherever possible, Mepsy references precise stock, sales, and energy performance data from recent CLASP in-country market studies, or country-level estimates from reputable market research firms. Where country-level data for a particular product are not available, calculations are based on estimates from regional or global averages, accounting for differences in country population, economics, or climate as relevant to a particular appliance. Future and past shipments are extrapolated based on recent trends.

Mepsy output screen

View model outputs by country

At the country level, view customer-level policy impacts such as appliance lifecycle costs, as well as national-level changes to energy use, carbon dioxide emissions, and the number of appliances in use as a result of the chosen policy scenario

Mepsy's calculation methodology has been used for decades to evaluate efficiency policy options

The model inputs and results can be downloaded as a data file to support further analysis offline.

Analyzing policies with multiple tiers

Sometimes multiple-tiered policies need to be analyzed, where a package of increasingly stringent policies is implemented over several years. With the downloadable data, you can view combined impacts all in one place.

Combine multiple sets of data into one multiyear policy package with our how-to

To use Mepsy to analyze policies that have changing efficiency requirements over a number of years, follow our how-to guide and download the template. Please contact us at with any questions.

More questions about Mepsy? Check out the FAQ or contact us.


Other Resources


Introduction to Mepsy
Mepsy Quick-Start Guide
How to Evaluate and Prioritize Efficiency Policies with Mepsy webinar – 27 April 2021
How Mepsy Can Transform Your Energy Efficiency Policy Development webinar – 16 March 2022



Mepsy Methodology and Assumptions – A summary of the methodology used for appliance model forecasting
Methodology FAQ – More detailed explanations of the methodologies
Extending Mepsy Past 2030 – Full methodology for our extension model (currently until the year 2050)
Global Refrigerant Impact from 6 Appliances in 22 Countries – Full methodology for calculating the impacts of conventional refrigerants, to be integrated into Mepsy in the future


Past Updates

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