This paper analyses the use of a battery energy storage system (BESS) in a domestic dwelling to determine whether it can provide a cost-effective investment for the homeowner. The battery is controlled using a rule-based algorithm to capture excess PV generation, and charge overnight so that the battery can then be used to supply house demand during peak tariff periods. A three rate Time of Use tariff is used to guide the battery operation. The case study examined is based on real data from a house in the UK, captured with a one-minute resolution over a one-year period. Results are used to examine the cashflow, payback period and internal rate of return (IRR) of the investment is this system. A sensitivity analysis is undertaken to determine the best BESS size which to achieve a payback over a 10 year period. The results obtained shows that the best battery capacity is 7 kWh in this case study. The battery power limitation is 2 kW, and the investment achieves a 13.14% IRR value.