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 link 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 lifetime cashflows break even. 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 — the number payback and NPV are measured against.
Depreciation tax benefit
Adds a yearly tax saving to the cashflow using straight-line depreciation: the net system cost (after upfront incentives like STCs, VEECs and PDRS) is spread evenly over the asset life, and each year's share is multiplied by the company tax rate. 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. It assumes the client is a business that can use the deduction — their accountant should confirm eligibility.
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.
Self-sufficiency
The share of the site's consumption met by its own solar and battery (self-used energy ÷ total load, capped at 100%). Distinct from load offset: self-sufficiency counts only energy you actually use on site, so exports never inflate it.
Load offset
Total solar generation as a share of the site's consumption, including exported energy — so it can exceed 100% on an oversized system. Compare with self-sufficiency, which counts only the generation used on site; the two coincide only when nothing is exported.
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.