Can home battery storage revolutionize the market for domestic pv systems?

The recent disclosure of the Tesla Powerwall home battery system has been seen by many as a catalyser for a solar energy revolution, and has created high expectations in the sector. Many observers have predicted an uptake of combined PV/Battery units, which, according to them, could ultimately disconnect from the grid and lead to autonomous homes or mini-grids. However, most of the comments originating from social media, blogs or press articles lack proper cost evaluation and realistic simulations. This short, preliminary analysis aims at bridging this gap. It is part of a continued effort on technology watch, assessment and market valuation studies related to storage technologies. Disregarding the current media impact and emotions related to it, this analysis demonstrates through a realistic test case that: 1. Although decreasing at a fast pace, the cost of domestic Li-Ion storage is most likely still too high for a large-scale market uptake in Europe, 2. PV incentives based on net metering are not favourable to home batteries, 3. Home battery profitability and future uptake mainly depend on the indirect self-consumption subsidies provided by the structure of the retail prices, 4. These systems do not allow residential consumers to go off-grid. They only allow for a maximum self-sufficiency ratio close to 70%. The calculation files related to this note including all equations and hypotheses as well as the input data are available upon request