Impacts of the active power demand measurement-time resolution on the financial attractiveness of domestic solar hot water systems

Abstract

This work assesses the electricity consumption profile of domestic solar hot water systems (DSHWS) and analyses, at high measurement-time resolutions for the first time, their economic viability in popular housing projects in Brazil. It analyses the impacts of the active power demand measurement-time resolution on the financial attractiveness of DSHWS. The predominance of a late-evening profile of electricity consumption for showering, coinciding with distribution utilities’ peak demand hours, leads to over 40% avoided active power during peak hours per consumer unit when adopting DSHWS. There is potential to finance DSHWS in popular housing with very favourable conditions for the distribution utility. For discount rates ranging from 0 to 9.5%, payback times ranged between less than four and five years, NPV between $ 2,191 and $ 782, and IRR between 25% and 14%. The measurement of power demand at 15-min intervals, widely adopted by distribution utilities, is not adequate to properly evaluate the financial attractiveness of DSHWS, resulting in pessimistic financial analyses of the return on investment. The low load-factor of electric showerheads used in >90% of Brazilian households, leads to the accounting of only 37% of the real avoided cost of adopting DSHWS when measuring power demand in 15-min intervals.