The short answer
The right answer depends on annual electricity use, available roof space, shading, installation complexity and whether the home can use electricity while the panels are generating. That sounds obvious, but it is where many weak solar estimates go wrong.
A good solar decision starts with demand, then checks the roof, then tests the money. Starting with the biggest system that fits can leave the homeowner exporting more power than expected at a lower rate.
Cost and sizing checks
Compare system sizes against annual usage rather than bedroom count alone. Bedroom count is a rough hint, not a design method. A small home with an EV can use more electricity than a larger home with gas heating and low daytime demand.
Ask installers how many panels are proposed, what wattage each panel has, what annual generation is expected and how shading has been allowed for. If the quote cannot explain those basics, the price is not ready to compare.
| Check | Why it matters | What to ask |
|---|---|---|
| Usage | Savings depend on avoided grid imports | What annual kWh figure are we designing around? |
| Roof | Direction and shading affect generation | Which roof faces are included in the model? |
| Battery | Storage can help but adds cost | How much export would the battery reduce? |
| Installer | Paperwork matters after fitting | Will the system be MCS certified? |
Common mistake to avoid
The common mistake is treating a solar quote as if it were a kitchen appliance price. It is really a small building and electrical project with a financial model attached.
Read the quote for design logic. Price matters, but the assumptions behind the price matter just as much.
Common questions
Should I get a quote before doing calculations?
A rough calculation helps you spot unrealistic claims, but a proper quote is still needed for roof layout, access, equipment and electrical checks.
Can one installer quote tell me the market price?
Usually no. Get more than one quote so you can compare equipment, design assumptions, warranties and installation scope.