Everything you need to know about the Ohm Equity energy efficiency calculator.
Ohm Equity is a free energy efficiency calculator that helps Australian homeowners figure out which energy upgrades deliver the best return on investment. You enter your postcode, home details, and energy setup, and it ranks every major upgrade (solar panels, battery storage, heat pumps, insulation, EVs, and more) by their total profit in today's dollars.
The calculator estimates your baseline energy usage based on your climate zone, home size, and whether you have gas. It then models each upgrade's upfront cost, annual energy savings, maintenance, and applicable government incentives. Crucially, it evaluates upgrades in sequence: each upgrade changes your energy profile, which affects the value of the next one. The algorithm finds the order that maximises total value across your whole upgrade roadmap. See our How We Calculate page for full details.
Simple mode asks for your postcode, number of bedrooms, home age, and a few toggles (gas, EV, smart meter). It uses sensible defaults for everything else. Advanced mode lets you enter your actual electricity bill, gas usage, tariff type (flat or time-of-use), appliance ages, floor area, roof orientation, and annual kilometres driven. The more detail you provide, the more accurate the estimates.
Ohm Equity does not require accounts. All calculations run in your browser; nothing is saved to our servers. Use the Download Report button if you want a copy.
No. All calculations run entirely in your browser. Your postcode, home details, and energy inputs are never sent to our servers or shared with third parties. We use Cloudflare Web Analytics for anonymous traffic data only. See our Privacy Policy for details.
The profit figure is the net present value (NPV) of the upgrade: your total gain in today's dollars after subtracting all costs from all savings. It accounts for the fact that money saved in the future is worth less than money saved today. If an upgrade shows $5,000 profit, that means it's $5,000 better than investing the same money in an index fund over the same period.
The 8% discount rate reflects the opportunity cost of capital, roughly what you could earn by investing the same money in a diversified index fund, adjusted downward slightly because home-energy savings are more certain than share returns. Long-run nominal equity returns sit around 8 to 10 percent; we use 8 percent so the bar is still high while giving the greater certainty of energy savings its due. If you prefer a different benchmark, you can adjust this in the "Under the Hood" panel.
The payback period is how many years it takes for an upgrade's cumulative savings to equal its upfront cost. A solar system with a 4-year payback means it pays for itself in 4 years, then everything after that is profit. Note that payback period doesn't account for the time value of money, that's what the profit figure is for. We show both so you can evaluate upgrades from different angles.
Because each upgrade changes your energy profile, which affects the value of the next one. For example, if you install ceiling insulation first, your heating and cooling costs drop, which means you need a smaller (cheaper) solar system. If you switch from gas to a heat pump hot water system, your electricity usage goes up, which increases the value of solar self-consumption. Our algorithm finds the order that maximises the total value across all upgrades.
Yes. Click "Under the Hood" on the calculator page to see and adjust all assumptions including your electricity rate, gas rate, discount rate, escalation rates, and equipment costs. Your overrides are used for that session only; we don't store them.
We size the system to offset roughly 80% of your annual electricity consumption, adjusted for your climate zone's peak sun hours (which range from 4.0 hours in cool climates to 5.5 in tropical areas). The cost is based on the current national average of $1.15 per watt before incentives, sourced from SolarChoice installer surveys. See our solar cost and savings breakdown for a state-by-state comparison.
Small-scale Technology Certificates (STCs) are a federal government incentive that effectively reduces the upfront cost of solar panels. The number of certificates you receive depends on your system size, location, and how many deeming years remain (currently 5 years, until 2031). At the current certificate price of around $39, STCs typically reduce the cost of a residential solar system by $2,000–$5,000. Our calculator factors this in automatically.
Yes, when the car can be home for it. We assume you optimise: on the days the car is at home in daylight (most days for households that are home, weekends for commuters, or your own answer in the refine panel) it charges first from a free daytime window if you are on one, then from surplus solar, then from the grid; the rest charges overnight at off-peak rates where you have them. Where a regulated free window is available (Solar Sharer in NSW, south-east Queensland and SA, the Midday Power Saver in Victoria from 1 October 2026) we assume you would take it if it saves money after the plan's dearer peak rate and higher supply charge. Set "On a free daytime power plan" in the refine panel if you already have one.
More often than it did a year ago. Installed prices have fallen to about $10,000 for 10 kWh and $14,250 for 15 kWh before the federal rebate, and on an existing solar system the battery sized to your evening load pays back in roughly six to eight years in most states. It does better again on a time-of-use plan, with the Cheaper Home Batteries rebate, in a Virtual Power Plant (VPP), or where a free daytime power window lets it charge from the grid for nothing. Our calculator models all of this for your specific situation and picks the size that earns the most, which is usually 10 to 20 kWh. For a full state-by-state breakdown, see our home battery deep-dive.
Your estimated electricity and gas bills for one year, before and after every recommended upgrade is in place. The before year is at your current rates, and if you enter your last 12 months of bills (or kWh) in the refine panel it is your bill rather than an estimate. The after year is at whichever is cheaper for your home once the upgrades are in: the flat rate, or the free daytime window plan with its dearer evening peak and lower feed-in. We replay the roadmap to its end state, price the electricity you would still import, add the daily supply charge, and subtract what your exports earn at the feed-in tariff. Gas disappears once the last gas appliance is switched. The figure almost never reaches zero: the supply charge stays as long as you are connected, and some winter-evening imports remain even with a battery. If the roadmap adds an EV, its charging is in the electricity figure while the petrol it replaces is counted in the EV step. It is an estimate of running costs, not advice.
A Virtual Power Plant is a network of home batteries that can be coordinated to supply power back to the grid during peak demand. In return, you earn credits or payments, typically around $300 per year. Our calculator includes VPP revenue for battery upgrades in NEM states where you also have solar installed.
Most households save $300–$600 per year by switching from gas to a heat pump hot water system, depending on your gas rate, usage, and climate zone. Heat pumps use a compressor (like a reverse-cycle air conditioner) to heat water, making them 3–4.5 times more efficient than gas. Combined with government rebates (which vary by state), many households see a payback period of 3–5 years.
If you have gas, we break the "switch off gas" into three independent upgrades: cooktop to induction, hot water to heat pump, and heating to reverse cycle. This is because each has a different cost, payback, and priority. For example, an induction cooktop is the cheapest switch and often makes sense first, while reverse-cycle heating is a larger investment that depends on your climate zone. The sequencing algorithm evaluates them independently so you can do them in the order that delivers the best return.
Your electricity bill will go up because you're replacing gas energy with electrical energy. However, the key insight is that heat pumps and induction cooktops are far more efficient than their gas equivalents: a heat pump delivers 3–4.5 units of heat for every unit of electricity, while a gas heater converts less than 1 unit of gas to 1 unit of heat. So while your electricity bill increases, your total energy cost drops. Plus, you eliminate your gas supply charge (typically $0.50–$0.85/day), which saves $180–$310 per year just in fixed charges.
We only recommend ceiling insulation for homes older than about 15 years. Homes built after 2010 are required to meet minimum insulation standards under the National Construction Code, so adding more insulation typically doesn't deliver a meaningful return. Older homes benefit the most: a pre-1960s home can save 30–40% on heating and cooling costs with proper ceiling insulation.
For older homes, draught sealing is often the highest-return, lowest-cost upgrade available. At around $1,000 for a typical home, it can reduce heating and cooling energy by up to 18–27% by stopping air leaks around doors, windows, vents, and floorboards. It's especially effective in pre-1980s homes where gaps accumulate over decades. Like insulation, it's not recommended for newer homes (less than 10 years old) that were built to modern sealing standards.
Unlike other upgrades, we don't assume you'll buy an EV immediately. The calculator looks at the age of your current car and estimates when it will reach end of life (based on an average 7-year lifespan). At that point, you'll be buying a car anyway, so we only count the price premium of choosing an EV over a comparable petrol car, not the full EV price. This "incremental cost" approach gives a more realistic picture of whether going electric is worth it.
If your current car is relatively new, it doesn't make financial sense to replace it early just to get an EV. The calculator delays the EV upgrade until your current car reaches end of life. For example, if your car is 3 years old, the EV upgrade is deferred by about 4 years. During sequencing, other immediate upgrades (like solar or insulation) are prioritised first, with the EV slotting in at the right time.
When your current car reaches end of life, you'll spend money on a replacement regardless. The incremental cost is the extra amount you'd pay to choose an EV over a similar petrol car. We model three tiers: budget (~$5,000 premium), mid-range (~$8,250), and premium (~$15,000). The savings come from cheaper fuel (electricity vs petrol at $2.30/L), lower maintenance (~$500/year less), and reduced servicing costs over the EV's 12-year lifespan.
Our estimates are based on publicly available data from the Australian Energy Regulator, Clean Energy Regulator, Bureau of Meteorology, and state government incentive programs. Equipment costs come from industry installer surveys and manufacturer pricing. The estimates are designed to give you a reliable ballpark for comparing upgrades. Your actual costs will vary based on installer quotes, specific equipment, and your usage patterns. We always recommend getting 2–3 quotes for any upgrade you decide to pursue.
Electricity rates are sourced from the Australian Energy Regulator's Default Market Offer and state-specific reference prices. We use state-level defaults ranging from 27c/kWh in Victoria and Tasmania to 43c/kWh in South Australia. Gas rates come from state energy comparators and published tariff schedules. All rates can be overridden in the "Under the Hood" panel if you know your exact tariff.
We model the major federal and state incentive programs including: federal STCs for solar, Victoria's Solar Homes and VEU programs, NSW Energy Savings Scheme, Queensland's interest-free loan scheme, ACT's Sustainable Household Scheme, South Australia's Retailer Energy Productivity Scheme, and Tasmania's Energy Saver Loan Scheme. Rebate amounts and eligibility rules are based on the latest published program guidelines. If a program has changed recently, please let us know.
Currently Australia, all states and territories. We plan to add more countries in the future.
We update electricity rates, gas rates, incentive programs, and equipment costs regularly as new data becomes available. Government incentive changes are typically reflected within a few weeks of announcement. If you spot an outdated rate or incentive, please contact us.
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