Public long-term care (LTC) systems provide services to support people experiencing difficulties with their activities of daily living. This study investigates the marginal effect of changes in public LTC expenditure on care-related quality of life (CRQoL) of existing service users in England. The public LTC program for people aged 18 or older in England is called Adult Social Care (ASC) and it is provided and managed by local authorities. We collect data on the outcomes and characteristics of public ASC users, on public ASC expenditure, and on the characteristics of local authorities across England in 2017/18. We employ an instrumental variable approach using conditionally exogenous elements of the public funding system to estimate the effect of public ASC expenditure on user CRQoL. Our findings show that by increasing public ASC expenditure by £1000 per user, on average, local authorities increase user CRQoL by 0.0030. These results suggest that public ASC is effective in increasing users' quality of life but only to a relatively small extent. When combined with the other potential effects of LTC expenditure (e.g., on informal carers, mortality), this study can inform policy makers in the United Kingdom and internationally about whether social care provides good value for money.