What drives the installed cost?
System size matters, but access can matter just as much. Scaffolding, roof condition, electrical upgrades, bird protection and whether panels span several roof faces can change the quote. Hearthline uses the published central benchmark as a starting point and applies a range rather than pretending every roof is identical.
What drives the saving?
Electricity used in the home is usually more valuable than electricity exported. Someone working from home, charging an EV or running appliances during daylight may self-use more than a household that is empty all day. A good quote should separate self-consumption, export and the unit rates assumed.
Do not accept one unexplained “annual saving”
Ask for annual generation in kWh, the assumed percentage used in the home, the export rate, degradation and whether the estimate includes a battery.
Should the battery be included?
A battery can increase solar self-use and make time-of-use tariffs useful, but it adds cost, conversion losses and a finite cycle life. Compare the solar-only case with the solar-plus-battery case. The battery should justify itself separately.
What a useful solar quote should show
- Panel count, wattage, inverter rating and usable battery capacity.
- Roof-specific annual generation with orientation and shading assumptions.
- Self-use and export assumptions stated separately.
- Scaffolding, electrical work, monitoring and making good included or excluded.
- MCS certification, consumer-code membership and warranty terms.