The answer
What should be fixed before phase one?
A phased project needs a picture of the intended end state before the first installation. Otherwise a later heat pump, array or battery can force expensive changes to cables, plant space or controls that were just installed.
01 / 02
Map dependencies first
List the final heating load, solar roof area, storage purpose, EV charging and expected electrical demand. Mark shared work such as roof repairs, distribution-board upgrades and cable routes. Some early work is worthwhile by itself; other work only makes sense if a later phase is affordable and permitted.
02 / 02
Create decision gates
For each phase, record the evidence, permissions and budget needed before it starts. Specify how the first system will be commissioned and then recommissioned when another technology is added. Compare whole-project cost and disruption with the apparent affordability of each individual stage.
Where this guidance comes from
Check the original guidance.
These primary sources support the technical or scheme points above. Rules can change; follow the current source before making a commitment.
Apply this to your property
Plan the order before buying phase one.
FLO's free survey can look at the property as a whole and identify which first step preserves later options.