Most Australian homeowners know that solar panels, batteries, and heat pumps can save money. The data is everywhere. Government rebate programs are well publicised. Energy bills arrive quarterly with a sting that gets harder to ignore. And yet, the most common response is still "I'll get around to it."
That's understandable. These are big purchases. They require research, quotes, and a willingness to spend thousands upfront. It is easier to wait. But waiting has a cost, and it is not a vague or theoretical one. It is a specific dollar figure that compounds every year.
This post uses real calculator data for three cities (Sydney, Melbourne, and Brisbane) to show what that cost looks like. Not projections. Not hypotheticals. Just the numbers, run through the same model anyone can use on the calculator.
How these numbers were calculated
All figures come from the Ohm Equity calculator. The analysis uses a 10% discount rate, which matches the long-run return of a broad stock market index. This is a high bar: if an upgrade beats the 10% benchmark, it is genuinely a better use of your money than investing it. The time horizon is 15 years. All profit figures are in today's dollars. Federal and state rebates are current as of April 2026.
The full picture: what all upgrades save over 15 years
Before looking at what delay costs, here is the baseline. The calculator sequences every worthwhile upgrade in optimal order: solar and battery first, then EV, heat pump hot water, gas appliance switching, and other applicable improvements. The total savings across all upgrades, after accounting for upfront costs and rebates, look like this:
| City | Total investment | 15-year savings | Profit (today's $) |
|---|---|---|---|
| Sydney (2150) | $34,109 | $128,839 | $31,044 |
| Melbourne (3150) | $39,597 | $125,459 | $23,458 |
| Brisbane (4122) | $30,244 | $107,609 | $24,730 |
These savings reflect all upgrades combined, not just solar panels. They include reduced electricity bills from solar and battery, eliminated gas supply charges and gas usage (for homes that switch off gas entirely), lower fuel costs from switching to an EV, feed-in credits from excess solar exported to the grid, and efficiency gains from heat pump hot water. The profit column is what remains after subtracting the total investment and discounting everything at 10% per year. In other words, this full portfolio of upgrades beats the stock market.
That is the prize. Now, what happens if you delay claiming it?
The compounding effect
Missing one year of savings is bad enough. But the real cost of waiting is that the gap keeps widening. You lose the early savings entirely, and you also lose the benefit of those savings compounding (or, more precisely, of not paying compounding energy costs). On top of that, federal STC rebates decline each year by design. A system installed in 2027 gets fewer STCs than the same system installed in 2026, which means the upfront cost goes up.
Here is how the total portfolio savings accumulate over time for each city, starting today versus delaying by 1, 2, or 3 years. These figures cover the full upgrade portfolio (solar, battery, EV, heat pump, and other applicable upgrades).
| City | Start now (15 yr savings) | Delay 1 yr | Delay 2 yr | Delay 3 yr |
|---|---|---|---|---|
| Sydney | $128,839 | $119,820 | $112,090 | $103,070 |
| Melbourne | $125,459 | $116,677 | $109,149 | $100,367 |
| Brisbane | $107,609 | $100,076 | $93,620 | $86,087 |
In Sydney, waiting three years costs roughly $25,800 in total portfolio savings. That is not a rounding error. It is enough to buy a decent used car. In Brisbane, the gap is about $21,500. In Melbourne, about $25,100. The pattern is consistent across all three cities: each year of delay costs roughly $7,500 to $9,000 in forgone savings from the combined upgrade portfolio. These estimates are conservative: they do not account for declining federal STC rebates or expiring state programs, which would push the upfront cost higher each year you wait. The real cost of delay is likely worse than the table shows.
But what about the upfront cost?
This is the most common objection, and it deserves an honest answer. Solar and battery systems (specifically) are not cheap. The net cost after rebates is $18,084 in Sydney, $18,964 in Brisbane, and $21,732 in Melbourne. That is real money.
But look at the solar and battery payback periods:
- Sydney: 4.5 years (saving $3,887 in year one)
- Brisbane: 5.0 years (saving $3,669 in year one)
- Melbourne: 7.4 years (saving $2,808 in year one)
It is also worth noting that the total investment figures show actual out-of-pocket costs, but many of these upgrades replace appliances you would need to replace anyway. For example, if your gas hot water system is at end of life, you would spend around $2,300 on a new gas unit regardless. The real incremental cost of switching to a heat pump is the difference: roughly $1,700. Similarly, the EV cost shown ($8,250) already reflects only the premium over buying an equivalent petrol car. So the true additional cost of electrification, above what you would spend anyway on replacements, is significantly lower than the total investment figure suggests.
After the payback period, the solar and battery system is effectively free. Every dollar it saves after that point is pure profit. In Sydney, that means 10.5 years of profit on a 15-year analysis. When you add the remaining upgrades (EV, heat pump, gas switching, and others), the total portfolio profit (all upgrades combined, discounted at 10%) is $31,044 in Sydney, $23,458 in Melbourne, and $24,730 in Brisbane.
To be clear: these profits are calculated after discounting future savings at 10% per year. That means these upgrades beat investing the same money in the stock market. Not by a little. By tens of thousands of dollars.
For homeowners who cannot pay upfront, financing options exist. Green loans and state-backed programs (like the ACT's Sustainable Household Scheme) offer low-interest pathways. Even with interest costs, the maths tends to work when the payback period is under 5 years.
Rebates won't last forever
The federal Small-scale Technology Certificate (STC) scheme is designed to phase out. Every year, the number of deeming years decreases, which means fewer STCs per system, which means a smaller rebate. The scheme ends entirely in 2030. A system installed in 2026 gets more STCs than the same system installed in 2027, 2028, or 2029.
State programs have their own constraints. Victoria's Solar Homes program has household income caps and a limited budget. Queensland's Battery Booster ended in 2024. Programs that exist today are not guaranteed to exist next year.
None of this is speculation or fear-mongering. It is how the programs are structured. The incentive landscape for home energy upgrades is, by design, the best it will ever be right now. Next year it will be slightly worse. The year after, worse again. This is written into the legislation.
What if I'm selling soon?
Even on a short time horizon, the numbers tend to work. Solar and battery pays for itself in 4.5 years in Sydney and 5.0 years in Brisbane. If you are planning to sell in 5 to 6 years, you will have recouped your investment and then some.
There is also the resale value question. Upgraded homes sell for more. The ACT already requires Energy Efficiency Rating (EER) disclosure at the point of sale, and other states are expected to follow. A home with solar, battery, and a heat pump is a more attractive purchase than one running on grid electricity and gas.
The upgrade order post covers which upgrades to prioritise if you have a shorter time horizon.
The bottom line
The cost of waiting is not abstract. A typical Sydney home stands to save $128,839 over 15 years by completing all worthwhile upgrades (solar, battery, EV, heat pump, gas switching, and more). Melbourne: $125,459. Brisbane: $107,609. Every year you delay, you lose a share of those savings permanently, and the rebates available to offset the upfront cost get smaller.
Over a full 15-year analysis, starting today versus waiting three years costs roughly $21,500 to $25,800 in forgone savings across the full upgrade portfolio, depending on where you live. That is the price of procrastination, calculated in today's dollars.
The calculator will show you the exact figures for your postcode, your energy rates, and your specific appliances. The numbers in this post are for typical homes. Yours may be higher or lower. But the direction is always the same: the best time to start is now.