Effects of flat-rate versus volumetric pricing on per capita water usage in western Kenya

Isaac Wafula Simiyu; Consolata Ngala; Edwin Simiyu

doi:10.51867/scimundi.5.2.33

Authors

Isaac Wafula Simiyu
isaacsimiyu@gmail.com
Masinde Muliro University of Science and technology, Kenya https://orcid.org/0009-0000-2922-7522
Consolata Ngala Masinde Muliro University of Science and technology, Kenya https://orcid.org/0000-0003-3629-4947
Edwin Simiyu Masinde Muliro University of Science and technology, Kenya https://orcid.org/0000-0003-0655-4971

Keywords:

Flat-Rate Pricing, Per Capita Usage, Tariff Structures, Utility Management, Volumetric Pricing, Water Demand, Western Kenya

Abstract

The design of water tariff structures is a critical policy tool for balancing cost recovery, equity, and demand management, especially in resource-constrained regions. In Western Kenya, utilities employ both flat-rate and volumetric pricing models, but their comparative effectiveness in influencing consumption behavior remains empirically underexplored. This study investigates the effects of flat-rate versus volumetric pricing on per capita water usage among households in Western Kenya. Utilizing a quantitative causal-comparative design, secondary panel data (2009–2024) from four county water utilities (Bungoma, Busia, Kakamega, Vihiga) were analyzed. Descriptive statistics summarized consumption trends and equity (Gini coefficient), while multiple regression analysis assessed the significance of each pricing model on water demand. Households under flat-rate pricing consumed significantly more water (Mean = 45.8 liters per capita per day, SD = 11.4) compared to those under volumetric pricing (Mean = 33.2 l/c/d, SD = 9.1). The Gini coefficient was higher under flat rates (0.54) than volumetric pricing (0.37), indicating greater consumption inequality. Regression analysis confirmed that volumetric pricing had a statistically significant effect on water consumption (β = 0.693, p = .016), whereas flat-rate pricing did not (β = 0.816, p = .054). A price structure change revealed that low-income flat-rate users increased consumption, while their volumetric counterparts reduced it. Volumetric pricing is a more effective mechanism for promoting water conservation and equitable use compared to flat-rate systems. Policy efforts should prioritize the phased expansion of metering infrastructure and the design of context-sensitive, pro-poor tariff structures that leverage the efficiency of volumetric pricing while safeguarding affordability through lifeline blocks.

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