Solar Cost per kWh Generated Calculator

How the solar cost per kwh generated works

Lifetime generation is annual output times the number of years. Lifetime cost is the system cost plus yearly maintenance across the same period. Dividing lifetime cost by lifetime generation gives the levelised cost of each kWh the system produces. If you enter a grid price, the tool shows whether solar comes in cheaper or dearer per kWh.

What you enter

Enter the system cost, annual generation, lifespan and maintenance; the calculator returns the lifetime cost per kWh and compares it with a grid price. Every field is editable, and the result recalculates the moment you change a value.

Reading the result

A cost per kWh below your grid price means the system generates cheaper energy than you buy. The figure ignores the time value of money, so treat it as a simple levelised cost rather than a discounted one.

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

This is undiscounted — it does not apply an interest or inflation rate to future years. Grid prices and tariffs change and are entered by you, not embedded. Panel output also drifts down slowly over the years, which a flat annual figure does not capture.

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.