A savings figure in a solar quote is a forecast built from assumptions, and modest changes to those assumptions can double the headline number. Before you trust it, ask for the inputs in writing: how much the system is expected to produce, what share you are assumed to use at home, what you pay for grid power, what you receive for exports, whether prices are assumed to rise each year, and whether panel degradation and shading are included. If a quote cannot show these, treat the savings claim as marketing rather than analysis.

The assumptions behind every savings estimate

Self-consumption: the number that matters most

Solar you use at home avoids grid electricity that commonly costs 30-45 c/kWh, while solar you export typically earns only a few cents. An estimate that assumes you use most of your solar directly will therefore show far larger savings than one that assumes you export most of it. A household with people home during the day, running air-conditioning or a home office, genuinely uses more. A household where everyone leaves by eight and returns after six uses much less, unless it has a battery or moves loads such as the pool pump and hot water into daylight hours.

Check the assumed percentage against how your household actually lives. If a quote assumes you will use most of your solar but the house is empty on weekdays, ask for the estimate to be rerun with a lower figure and compare the difference.

Tariff escalation and long-term totals

Some quotes show savings over 20 or 25 years. Those totals often assume electricity prices rise by a fixed percentage every year, which compounds and can make the lifetime figure look very large. Prices can rise, fall or change structure, and feed-in tariffs in NSW have fallen. Ask for a version with flat prices. If the system still makes sense on flat prices, any future rises are a bonus rather than the foundation of the decision.

Production, shading and degradation

A 6.6 kW system in Sydney typically produces around 24-27 kWh a day on average across a year, but that range assumes a reasonable orientation and little shade. East- and west-facing panels, a low tilt, and shade from trees, chimneys or neighbouring buildings all reduce output, and with some designs partial shade on one panel can pull down a whole string. A credible estimate should reflect your actual roof, ideally after a site visit rather than satellite images alone.

Panels also lose output gradually, commonly around 0.4-0.55% a year. That is small in any single year but adds up over two decades, so a 25-year savings total that ignores degradation is overstated. Our panel efficiency guide explains how heat and panel quality affect real-world output.

Other claims worth questioning

• "Your bill will disappear." You still pay a daily supply charge, and winter production is lower. Solar reduces bills; it does not remove them.
• Battery savings counted every day of the year. A battery can only shift surplus solar it actually has, which is often much less in winter.
• VPP earnings treated as certain. Virtual power plant payments depend on the program's terms and how often the battery is used, and those terms can change.
• Incentives that no longer stack. The NSW household battery installation incentive has been suspended since 30 June 2025, so for most households it no longer adds to the federal battery discount. Our NSW incentives guide explains what currently applies; confirm values on the official pages before you sign.
• Savings on the wrong baseline. Savings measured against an old bill from before you added an EV or a family member are not a like-for-like comparison.

Rebuilding the estimate yourself

1. Take a year of bills and note your total usage, usage rates and feed-in tariff.
2. Use the quote's production figure, trimmed if your roof faces east or west or has shade.
3. Choose a cautious self-consumption percentage and an optimistic one.
4. Value self-consumed kWh at your usage rate and exports at your feed-in tariff.
5. Compare your range with the quote. If the quote sits well above your optimistic case, ask why.

Then compare two or three quotes for a similar system size. Production estimates for the same roof should be broadly similar, so an outlier is a signal to dig deeper. Our guide to choosing an installer covers the other checks worth making before you sign.

Signs an estimate has been done carefully

Not every savings figure is inflated. A careful estimate usually shares some clear traits:

• It is based on your bills or interval data, not a generic household.
• It states production, self-consumption, usage rate and feed-in tariff separately.
• It reflects your roof's orientation and any shading seen at a site visit.
• It shows a range or a flat-price case rather than one large lifetime number.
• It uses cautious words such as "typically" and "estimated", not promises.

Next steps

Ask every installer for their savings assumptions in writing, and rerun the numbers with flat prices and a realistic self-consumption share. For a close look at your current usage and tariff first, the Electricity Bill Audit is listed at $99 in the energy market, an indicative price. For a quote based on an in-home assessment of your roof, shading and usage, request a free assessment from Blue Energy Solar; system prices are confirmed after the site assessment.

Frequently asked questions

Is it a warning sign if a quote has no savings estimate at all?

Not necessarily. Some installers prefer not to forecast savings without your bills or interval data, which can be more honest than a generic figure. What matters is whether they explain the expected production for your roof and help you understand how your usage affects savings. If you want an estimate, send your bills and ask for one with its assumptions listed.

What self-consumption percentage should I assume?

There is no single right figure, because it depends entirely on your household. Work from your own pattern: look at interval data if you have a smart meter, note when major appliances run and who is home during the day. Then test a cautious and an optimistic percentage. The gap between the two results shows how much your decision depends on this one assumption.

Can I complain about misleading savings claims?

Yes. Under the Australian Consumer Law, businesses must not make misleading claims. If you believe a quote or sales pitch misrepresented likely savings, keep copies of the quote and any written material, raise the issue with the business first and, if that does not resolve it, contact your state's fair trading office for guidance on your options.