The visible assumptions define the boundary of this calculation.
This calculator is for planning and education, not legal, tax, medical, immigration, engineering or financial advice.
Use current official rates, contracts, carrier terms, statutes or professional guidance before relying on the result.
The default values are examples. Replace them with the figures from the job, invoice, contract, bill, service or record being checked.
Master’s Tip
How to use the result well
Professional note: print the input values, formula, result and date together so the calculation can be reviewed later.
Printable record
What belongs in the saved calculation
Save the inputs, result, formula, assumptions, page URL and date together so the calculation can be reviewed later.
System size
6.6 kW
System cost
8,000 $
Electricity tariff
0.28 $/kWh
Feed-in tariff
0.06 $/kWh
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Formula
Daily generation = system kW x 4. Self-used kWh = min(daily generation x 0.5, daily usage). Annual savings = (self-used x tariff + exported x feed-in tariff) x 365. Payback = system cost / annual savings.
Worked example
A 6.6 kW system at $8,000 with $0.28/kWh import tariff and $0.06/kWh feed-in tariff returns roughly a 6-year simple payback under the default assumptions.
Professional note
Professional note: print the input values, formula, result and date together so the calculation can be reviewed later.
Regional and unit assumptions
Basis: transparent planning arithmetic using the visible inputs and assumptions on this page.
Assumptions and limitations
This calculator is for planning and education, not legal, tax, medical, immigration, engineering or financial advice.
Use current official rates, contracts, carrier terms, statutes or professional guidance before relying on the result.
The default values are examples. Replace them with the figures from the job, invoice, contract, bill, service or record being checked.
Methodology & Accuracy
How this calculator is checked
CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.
Formula used
Daily generation = system kW x 4. Self-used kWh = min(daily generation x 0.5, daily usage). Annual savings = (self-used x tariff + exported x feed-in tariff) x 365. Payback = system cost / annual savings.
Standard or basis
Basis: transparent planning arithmetic using the visible inputs and assumptions on this page.
Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.
Master's Tip
Professional note: print the input values, formula, result and date together so the calculation can be reviewed later.
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