As a broad Wollongong guide, a replacement electric system may cost around $1,500–$3,000 installed, while gas systems can be roughly $2,000–$4,500. Heat-pump systems often cost about $3,000–$6,500, and solar hot water can be higher, depending on the household’s needs and roof setup. Your final price may change with tank size, difficult access, pipework, electrical upgrades, removal of the old unit and local labour rates. Ask a licensed Wollongong plumber for an itemised quote, and check energy.gov.au or NSW Government information for any rebates or incentives that may apply.