Une maison autonome en Wallonie. Analyse économique d'une maison unifamiliale entièrement indépendante des réseaux de distribution.

Abstract

During the last years in Wallonia, the number of households having installed distributed electricity sources, such as solar panels, has been continuously increasing. The same trend applies to the number of houses equipped with a rainwater collection system. In a general manner, people tend to gain more and more autonomy from the distribution networks, such as the electricity or the water grid. This will for more autonomy can be explained through three main factors: economical (profitability of the investment), ecological (limitation of environmental impact) and ideological (more control on supply). On a larger scale, autonomous houses could make the society more efficient, by avoiding to keep extending distribution networks to remote areas. The aim of this work is therefore to analyze the feasibility, on a legal and technical point of view, of a house completely autonomous from distribution networks (sewers, gas, electricity, water), and to analyze the financial impacts of such an investment. A reference project is chosen in the Province of Luxembourg : the costs of construction and use of this one-family home are compared to those that would be incurred if the same building was built with no connection to the distribution networks. Various commercially available technologies are used and combined to achieve this objective, such as rainwater collection and treatment, individual waste water-treatment units, fuel cell, biomass boilers, photovoltaic panels and generating sets. Different scenarios are compared, based on the Net Present Value that each investment generates. The conclusions show that even though it is legally and technically feasible to build an autonomous house, none of the scenarios are profitable in the 15-year-timeframe considered. In specific cases, plots isolated from already urbanized area could however benefit from autonomous houses, as the cost for network extension to remote areas can then be dissuasive. Evolution of future energy prices is hard to predict but has a large impact on the financial results, and the conservative hypothesis used coupled to installation costs likely to decrease may prove autonomy more profitable in the coming years. All the scenarios allow to lower the annual CO2 emissions compared to the reference house, but it is yet unrealistic to have an autonomous house supplied only by decentralized renewable resources. Leaving the network has also impacts on the society at a larger scale: by not contributing to the utilities’ fixed cost, their burden will be shared amongst the remaining users, hence creating a social unbalance. As for many other subjects linked to energy transition, the next moves of the lawmakers will be crucial to tackle these unavoidable changes of paradigm.