Solar Cost
Off-Grid vs Grid-Tie Comparison Calculator
Compare 25-year cost of off-grid against grid-tie
Updated 12 July 2026 · Live
What this tool does
Compares the long-run total cost of ownership of an off-grid system against a grid-tied one, including standing charges and grid usage.
Enter the cost of each path plus grid connection, standing charge, usage and price; the calculator returns the long-run total for both and the break-even.
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Formula Used
How the off-grid vs grid-tie comparison works
The off-grid total is its up-front cost plus an allowance for replacing batteries once over the period, since it buys no grid energy. The grid-tie total is its up-front cost plus the connection fee plus, for every year, the standing charge and the cost of the energy still imported. The break-even is how many years of grid running cost it takes to match the off-grid premium.
What you enter
Enter the cost of each path plus grid connection, standing charge, usage and price; the calculator returns the long-run total for both and the break-even. Every field is editable, and the result recalculates the moment you change a value.
Reading the result
Whichever total is lower wins over the period you set. The break-even year tells you how long the off-grid premium takes to pay back through avoided standing charges and imports — shorter is better for going off-grid.
Safe by design
This calculator does the arithmetic of sizing — quantities, geometry and cost. It deliberately stops at the line a certified installer must sign off. It will never tell you a cable or fuse size, an earthing arrangement, a battery charge voltage, or a roof structural load: those are regulated calculations where a wrong number causes fire, electrocution or collapse. All electrical work must be carried out by a qualified, certified installer, and this page is not an installation guide.
Assumptions and limits
All prices and charges are your own — tariffs and standing charges change and are not embedded. The comparison is undiscounted and uses a single battery-replacement allowance; real off-grid systems may replace batteries more than once, and grid prices rarely stay flat for 25 years.
Using it with the rest of BuildMetricLab
This calculator is one step in planning a system. Pair it with the other solar sizing, geometry and cost tools to go from an energy figure to a panel count, a layout and a costed bill of materials. Every BuildMetricLab tool runs entirely in your browser — no sign-up, nothing sent to a server, and the formula is shown on the page so the maths can be audited.
Sources & methodology
Compares the long-run total cost of ownership of an off-grid system against a grid-tied one, including standing charges and grid usage. Every result is calculated from the values you enter, all inputs are editable, and no time-sensitive prices or tariffs are embedded.
Frequently asked questions
Why is off-grid usually dearer up front?
Off-grid needs a much larger battery and often more panels to survive cloudy spells with no grid to fall back on, which raises the up-front cost.
What is the break-even year?
It is how many years of avoided standing charges and grid imports it takes to recover the extra up-front cost of going off-grid.
Are future price rises included?
No. The comparison holds prices flat and undiscounted. If you expect grid prices to rise, off-grid looks better than this simple figure suggests.
Why enter my own tariff?
Standing charges and unit prices differ by supplier and region and change often, so embedding them would mislead. Your own figures keep the comparison honest.
Spotted something off?
Calculations or display — let us know.