Financial Planning

Financing vs Cash Calculator

See whether it's better to pay cash (and lose savings interest) or finance the system — including loan interest, the savings interest you forgo, and energy price escalation. Every assumption is an input you can change.

System & Cost

System Cost (£)

Annual Energy Savings (£/yr)

System Lifespan (years)

Finance Details

Finance APR (%)

Finance Term (years)

Deposit (£)

Economic Assumptions

Savings Interest Rate (% — what your cash earns in the bank)

Advanced Options

Energy Price Escalation (%/yr)

Tax Rate on Savings Interest (%)

Cash — Net Benefit Over Life

Finance — Net Benefit Over Life

Winner

Cash Opportunity Cost

Monthly Finance Payment

Total Interest Paid

Cash Payback Period

Finance Payback Period

Net Benefit — Cash (nominal)

Detailed Comparison

Metric	Cash Purchase	Finance	Difference
Upfront Cost	-	-	-
Total Finance Costs	£0	-	-
Total Energy Savings (life)	-	-	-
Interest Forgone on Purchase Cash	-	£0	-
Interest Earned on Retained Cash	£0	-	-
Net Position (incl. interest effects)	-	-	-

How this is calculated

Both scenarios receive identical energy savings, escalated annually at the rate you set. The cash buyer pays the full cost up front and forgoes the after-tax interest that money would have earned over the system life. The finance buyer pays the deposit, keeps the remainder in savings earning after-tax interest, and draws the monthly repayments from that pot until it is exhausted. The winner is whoever ends the system life in the better net position. No inflation adjustment is applied to the headline figures — they are nominal. Finance APR, fees and eligibility vary by lender; this tool is for comparison, not a quote.