How to compare solar quotes

Quotes are rarely for the same thing. Making them comparable is most of the work.

Three quotes will typically differ in system size, panel and inverter make, what is included and how savings were calculated. Compared as headline prices they tell you almost nothing.

Step-by-step

1. Enter each quote — size, price, equipment, inclusions.
2. Read the normalised comparison, price per watt and estimated output.
3. Work through the checklist of what to ask each installer.

Normalise before judging

Price per watt, and estimated annual output per pound or dollar spent, are the two figures worth comparing. A larger, more expensive system may well be the better value.

What differs beyond price

• Panel efficiency, which matters mainly when roof space is the constraint.
• Inverter type — string, optimisers or microinverters. On a shaded roof this is a substantial difference in output, not a preference.
• Warranty terms, and crucially whether the installer is likely to exist to honour the workmanship warranty.
• Monitoring, and whether it requires a subscription.

The installer matters as much as the equipment

Panels are reliable and largely commoditised. Installation quality is where outcomes diverge — roof penetrations that leak, poor cable management, and undersized isolation are all installer problems, and all expensive to remedy.

Check how long they have traded, ask for local references, and confirm the relevant certification. A slightly higher price from an established installer is usually the better purchase.

Frequently asked questions

How many quotes should I get?

At least three, and preferably from installers of different sizes. The spread is usually wide enough to be informative about what is normal locally.

Is a more expensive quote better?

Sometimes it buys optimisers, a better inverter, or a more established installer with a workmanship warranty worth having. Sometimes it buys nothing. Ask what the difference is for.

What if an installer will not answer questions about assumptions?

Treat that as informative. An installer unwilling to say which self-consumption rate and export rate underlie their savings figure is not one to hand a large sum to.