Editorial policy

Who writes this

Everything here is written and built by Brendan Faulds, the site's founder. Brendan Faulds is the founder of Solar Pays Off. A software developer, he built the site’s payback engine and its data pipeline — which pulls from the U.S. Energy Information Administration, NREL and the IRS for the American pages, and from the Australian Energy Regulator’s Consumer Data Right and the Clean Energy Regulator for the Australian ones — and wrote the validator that refuses to publish a figure without a source, a date, a method and a licence. No lead forms, no solar-industry funding.

That is a specific and limited kind of expertise, and it is worth being straight about it: the competence behind this site is in data and modelling — sourcing public regulator data, building the payback engine, and being careful about what the numbers can and cannot show. It is not a licence to give you personal financial advice, and nothing here is that. We are not accredited installers, electricians, tax agents or financial advisers, and none of this substitutes for an itemised quote from someone who has looked at your roof.

Where the numbers come from

Every figure the site publishes is someone else's measurement, carried with its source, the date it describes, the method behind it, how much confidence it deserves, and the licence it is used under. That is enforced in code, not by habit: a number that cannot supply all of those cannot reach a page, and the build fails rather than publishing it.

• United States — electricity prices from the U.S. Energy Information Administration, solar yield from NREL's PVWatts model, incentive rules from the IRS and DSIRE. Full detail on the US methodology page.
• Australia — retail prices and feed-in tariffs from the Australian Energy Regulator's Consumer Data Right, solar zone ratings from the Clean Energy Regulator. Full detail on the Australian methodology page.

Where a figure is an assumption rather than a measurement — installed cost per watt, a representative household bill — the page says so in those words, and lets you replace it with your own. We would rather show you a stated assumption than a confident average with nothing behind it.

How often it is rechecked

Electricity prices move quarterly; solar yield is climatological and barely moves at all. Each figure carries a maximum age appropriate to what it measures, and the build refuses to publish one that has gone stale past it. Pages carry two dates, because they answer different questions. Data as at is when the figures themselves were last true — the period the underlying dataset describes. Page last revised comes from the actual change history of the page and the data behind it, not from the date the site was last rebuilt, which would make every page look freshly checked whenever a typo was fixed. A page revised today is not a page whose numbers changed today, and saying so plainly is more useful than one date pretending to mean both.

How the site makes money

This matters for reading anything on a site like this, so here it is in full:

• Advertising. The site carries display advertising. Ad positions are chosen by us and sit outside the calculators — never inside a results panel.
• Affiliate links. Some pages link to products; where they do, the link is labelled and we may earn a commission at no extra cost to you.
• What we do not do. There are no lead-capture forms and we do not sell, share or broker your details. We are not a solar installer and take no funding from the solar industry. No advertiser or affiliate has ever seen a page before it was published, and none can influence a figure — the numbers come from regulators, and changing one to flatter a product would require falsifying a cited source.

Nothing you type into a calculator leaves your browser. There is no account, no signup and no email required to use anything here.

About the images

The photographs on this site are illustrations, generated for it. They are not documentary photographs of real houses, real installations or real customers, and no image here should be read as evidence of anything. Each one carries that credit beneath it.

We say so plainly because the rest of this page is a promise about provenance, and that promise would be worth very little if the pictures quietly broke it. Illustrations set the scene; the numbers do the work, and only the numbers are sourced.

Corrections

If a number here is wrong or out of date, that is a bug and we want to know. Tell us through the contact page. Substantive corrections — anything that changes a figure a reader might act on — are fixed at the source of the data rather than patched on the page, so the same error cannot reappear elsewhere on the site. The page's last-reviewed date moves when it is fixed.

We would rather publish a smaller site that is right than a larger one that is plausible. Where a market or a region cannot be covered from licensed, citable data — Western Australia and the Northern Territory, for instance, which sit outside the national framework the Australian data comes from — it is left uncovered rather than estimated.