How to analyse a solar quote

Price per watt makes quotes comparable. The savings estimate is where the optimism lives.

Solar quotes are hard to compare because they differ in size, equipment and what is included. Reducing them to comparable numbers is the first step.

Step-by-step

1. Enter the total price and system size.
2. Enter the finance terms if it is not a cash purchase.
3. Compare price per watt against other quotes.

Price per watt, cash and financed kept separate

Total price divided by system size in watts gives the standard comparison figure. A larger system usually costs less per watt, because scaffolding, labour and the grid application do not scale with size.

A financed quote must be compared on its own terms. A headline price with finance attached can look competitive while total repayments exceed a higher cash quote substantially. The tool keeps them apart because collapsing them into one figure is how a more expensive system is made to look cheaper.

Check what is actually included

• Scaffolding — sometimes excluded and substantial.
• Grid application and any distribution network charges.
• Electrical work such as a consumer unit upgrade.
• Roof repairs found once panels are lifted.
• Warranties — panel, inverter and workmanship are three different things with three different terms.

The savings figure

Treat it as marketing until you know the assumptions. Ask which self-consumption rate, which export rate, and what electricity price inflation. A quote assuming 100% self-consumption and 8% annual price rises will show a payback roughly half what a cautious calculation gives.

Frequently asked questions

What is a reasonable price per watt?

It varies widely by country, system size and equipment, so compare against other local quotes rather than an international figure. Larger systems cost less per watt because fixed costs are spread further.

How do I compare a financed quote with a cash one?

Separately. Work out total repayments over the finance term and compare that with the cash price. A low headline figure with finance attached frequently costs more overall.

Which questions expose an optimistic savings estimate?

Which self-consumption rate was assumed, what export rate, and what annual electricity price inflation. Those three explain nearly every difference between an installer's payback figure and a cautious one.