Glossary
Plain-English definitions for the financial and energy terms used across Amperage: NPV, IRR, payback, export ratio, self-sufficiency, time-of-use tariffs, demand charges and more. Each term has a stable link so explainers elsewhere in the app can point straight at it.
Every term below is defined once, here. The in-app explainer popups render these exact definitions and link back to this page. Anchors are stable, so you can send a customer straight to a term.
NPV (Net Present Value)
The lifetime dollar value of a system in today's money: every year of modelled savings (minus the upfront cost) discounted back to the present at the discount rate. A positive NPV means the system earns more over its life than it costs; the "NPV Maximising" scenario simply picks the system with the largest one.
IRR (Internal Rate of Return)
The effective annual return the system earns on its upfront cost: the discount rate at which the system's cashflows break even. Amperage quotes the 10-year IRR, from the first 10 years of cashflow with nothing counted after year 10, the same figure on every page and export. Useful for comparing solar against other uses of the same capital: an IRR of 15% beats a term deposit at 5%.
Payback period
The number of years until cumulative savings repay the net upfront cost (after upfront incentives). Amperage uses escalated, degradation-aware savings plus any time-limited LGC revenue (not a naive cost ÷ year-one-savings division), so the figure matches the full cashflow model.
Capex (capital expenditure)
The upfront installed cost of the system. "Net capex" is that cost after upfront incentives (STCs, VEECs, PDRS) are deducted, and that is the number payback and NPV are measured against.
Depreciation tax benefit
Adds a yearly tax saving to the cashflow from depreciating the net system cost (after upfront incentives like STCs, VEECs and PDRS). Two methods: Straight line spreads the deduction evenly over the asset life: yearly benefit = net cost ÷ asset life × tax rate, e.g. $100,000 over 20 years at 30% adds $1,500 a year for each of those 20 years. Diminishing value front-loads it instead, using the ATO's 200% method on the reducing balance: each year's deduction = remaining balance × (200% ÷ asset life), so the tax benefit is largest in year 1 and shrinks every year after. Both assume the client is a business that can use the deduction, and their accountant should confirm eligibility and which method suits the asset. Instant Asset Write-off may let eligible businesses deduct the full cost in year one instead - thresholds and eligibility change, so confirm current rules with the client's accountant.
Export ratio
The share of the system's total generation that is exported to the grid rather than used on site. A low export ratio means most generation offsets your own (expensive) consumption; a high one means surplus is being sold at the (much lower) feed-in rate. The "Energy Ideal" scenario targets the export share that suits the site's load shape.
Use met on site (self-sufficiency)
The share of the site's consumption met on site: solar used as it is generated plus battery discharge to the load, ÷ total load, so it never exceeds 100%. This is the "N% of your use" figure on proposals and decks. Distinct from load offset: exports never inflate it. Battery discharge counts whether the battery was charged from solar or the grid.
Load offset (incl. exports)
Total solar generation as a share of the site's consumption, including exported energy, so it can exceed 100% on an oversized system. It is not the share of your use the system meets: compare use met on site, which counts only energy used on site. The two coincide only when nothing is exported and there is no battery.
Time-of-use (TOU) tariff
A tariff that charges different rates by time window, typically peak, shoulder and off-peak. Solar generates during daytime shoulder/peak windows, so each self-consumed kilowatt-hour on a TOU tariff is usually worth more than on a flat rate.
Demand charge
A charge based on your highest power draw (kW or kVA) in a billing period, separate from the energy (kWh) you consume. Solar only reduces it when the peak lands during generation hours; shaving an evening peak usually needs a battery discharging in the demand window.
Daily (supply) charges
Fixed charges billed per day regardless of consumption: the retailer supply charge, metering charges and similar. On bills Amperage extracts, all daily and fixed charges are unified into one list with a name, days, rate and total for each row.
Feed-in tariff (FiT)
The rate paid for each kilowatt-hour exported to the grid, typically a fraction of the retail import rate for commercial sites. Because exports earn so much less than self-use saves, sizing to maximise self-consumption usually beats sizing for generation alone.
ROI (Return on Investment)
Total lifetime savings as a multiple of the upfront cost, before any discounting. ROI ignores when the money arrives, so a system that pays back slowly can still show a high ROI. Read it alongside payback and IRR, which do account for timing.
LCOE (Levelised Cost of Energy)
The system's total lifetime cost divided by the energy it generates over its life, in cents per kilowatt-hour. It is the break-even price of your own solar power: when it lands below your grid import rate, every self-consumed kilowatt-hour saves money.
Discount rate
The annual rate that converts future savings into today's money in the NPV calculation. A higher discount rate weights near-term savings more heavily and distant ones less. Amperage defaults to a commercial figure you can override per project or per company.
Energy price escalation
The assumed yearly rise in grid electricity prices. Solar savings track the price you avoid paying, so a higher escalation makes the same system save more over time. Export (feed-in) prices escalate on their own path, and usually far slower, often flat.
Export price escalation
The assumed yearly change in the feed-in rate you are paid for exported energy. Feed-in tariffs rarely rise, so 0%/yr is typical; a negative value models a declining feed-in rate. It moves only the export side of the savings, never the grid price you avoid.
Self-consumption
The share of your solar generation kept on site (used as it is produced, or stored in the battery and used later) rather than exported. Self-used energy offsets expensive grid power while exports earn only the low feed-in rate, so high self-consumption is what makes solar pay. It divides by generation; use met on site divides by your consumption instead.
Panel degradation
The slow decline in a panel's output as it ages, quoted as a percent per year, commonly around 0.5%/yr. Amperage applies it across every year of the analysis, so later years generate, and save, a little less than the first.
DC/AC ratio
The ratio of panel (DC) capacity to inverter (AC) capacity. Above 1 the array is oversized against the inverter, which lifts output in weak light but clips a sliver of the midday peak the inverter cannot pass through. A modest amount of clipping is normal and usually worth it.
Battery dispatch
The rule that decides when a battery charges and discharges each hour. Storing surplus solar for the evening is always on; extra strategies (shaving a demand peak, or arbitraging cheap-to-expensive tariff windows) layer on where the tariff rewards them.
Battery dispatch modes
The three things a behind-the-meter battery can do for the site, and every active battery models all three unless you switch one off. Self-consumption stores surplus solar for the evening and is always on. Peak demand reduction holds charge back for the billed demand window and only earns where the bill has a demand charge. Energy arbitrage charges in cheap hours and discharges in dear ones, so it only earns when the price spread beats the arbitrage threshold: on a flat tariff it earns nothing. Grid charge off-peak lets the battery top up from the grid overnight for the next day’s peak, rather than from solar alone. The modes you leave on are what the sizing sweep ranks systems with: self-consumption alone gives the conservative ranking, any extra mode counts its dollars.
Battery adds value (matrix filter)
Hides battery squares worth less than the solar-only square at the same size. Display only: it does not change which systems are recommended.
Energy arbitrage
Charging a battery when power is cheap and discharging when it is dear, to earn the gap. On a time-of-use tariff that means charging off-peak and covering the evening peak; on a wholesale/spot tariff it means tracking the market price. Modelled capture sits below a perfect-foresight ideal because real dispatch cannot see the future.
Charge mix (bill breakdown)
Now figures are read straight from your bill, ex GST. With The System recomputes each category from your modelled post-solar usage at the same tariff rates, not a flat percentage cut applied to the old bill, so different categories can fall by different amounts. Any credit for solar exported to the grid is shown separately in the annual savings figures, not netted into any one category here.
Network tariff review
Where the site sits on its network tariff after your picked system goes in, and whether another tariff on the same network would be cheaper. Grid import before and after install is checked against the tariff's consumption band; every priced tariff for the segment is costed on both loads and badged Electable, Network assigned, Unverified or Not eligible. Network charges only, from the published FY2026-27 price list; any switch is arranged between the retailer and the network.
Additional loads (option adjustments)
An extra load a comparison option adds to the site before it is sized, so you can answer "what if they also put in an EV charger?" without touching Base. A profile load (from the Library, a typed pattern or an uploaded interval file) is added to the site load hour by hour; a growth load compounds the bill savings by a percentage a year for a set number of years. Each carries its own upfront cost, which is added to the option’s system price after incentives. An added load earns no STCs or LGCs. The added load is listed on the option card, the Options compared table, the deck’s comparison slide and the assumptions footer.
Export limit (option adjustment)
A network export cap applied to one comparison option: in every hour, solar export above the cap is curtailed and earns nothing, after the battery has taken what it can of the surplus. Self-consumption, grid import and the battery’s behaviour are unchanged; only the feed-in credit and the option’s payback and NPV move. 0 kW models a zero-export site. Most distributors set a fixed export limit for commercial connections, so an option with the cap shows what the sizing is worth once that is applied.
Period earnings (Energy Schedule)
The bill saving for one real day or week of the site’s interval data, split the same way as the annual savings composition. Every hour is priced at that hour’s import rate: solar direct to load is what the array met on site, battery to load is the import the battery avoided, export income is the feed-in credit, and grid charging is what the battery bought. The four add up to the grid cost before the system minus the grid cost with it, and summed over the whole year they equal the annual energy saving on the scenario card. Solar direct is solar’s own value and battery to load plus grid charging is what the battery adds, the same solar and battery slices as the card. Demand is billed on the month’s window peak, never on a day, so the demand tile shows the month’s saving and the day and hour that set the billed peak.