Buying a new boiler and having it installed will vary hugely in cost. You’ll need to factor in these elements when considering costs:
The type of boiler you want;
Whether this system will require extensive pipework;
How easily accessible your home is for boiler installation (e.g. transporting and installing a large tank);
How large the heating system will be (system boiler installation is typically more expensive);
Whether any old equipment will need to be removed and disposed of.