You hold Bitcoin and never sell it. Instead, you borrow against it. As Bitcoin grows in value, you can borrow more — always keeping the loan at a safe 50% of your collateral. The borrowed money funds your retirement income.
Each year, the loan interest is paid out of a reserve pot that you set aside from day one and top up annually. The reserve pot itself earns savings interest (after tax), working a little harder for you while it sits there.
The Annual Cycle — Step by Step
1Bitcoin appreciates
Your BTC grows at the annual rate you've set (default 15%). This increases your collateral value — for example, 3 BTC at £237,000 = £711,000 in Year 1, rising to £817,650 in Year 2.
2Refinance to 50% LTV
The loan is refinanced so that the total balance equals exactly 50% of the new collateral value. You always maintain 50% loan-to-value — no more, no less. The gap between the new loan amount and last year's balance is your "new draw".
3Reserve pot earns interest
Before anything else happens, the reserve pot earns savings interest. The gross interest is taxed (default 40%), and the net amount is added to the pot. For example, £259,500 in the pot at 3% gross, taxed at 40%, earns £4,671 net.
4New draw goes into the reserve pot
The fresh money from refinancing flows into the reserve pot, topping it up for the year ahead.
5Loan interest is paid from the reserve pot
The annual interest on the full loan balance (default 10% APR) is deducted from the reserve pot. This is the cost of borrowing.
6Your income is taken from the reserve pot
Your inflation-linked income (starting at £5,000/month = £60,000/year, rising 2.5% annually) is withdrawn from the reserve pot. This is your retirement income — tax-free, because it's a loan, not a sale.
How the Reserve Pot Works
The reserve pot is the heart of the model. Think of it as a savings account that acts as a buffer between your Bitcoin-backed loan draws and your monthly spending. Here's what flows in and out each year:
+Net savings interest earned on last year's balance
+New draw from refinancing (BTC growth unlocks this)
−Loan interest for the year (10% of total loan balance)
−Your annual income (inflation-linked)
If the pot stays positive, you're golden. If it turns negative, the model flags that year as a shortfall — meaning BTC growth hasn't kept pace with your outgoings.
Worked Example — Year 1 (January 2028)
Using the default inputs:
Starting position
BTC held3.00 BTC
BTC price£237,000
Collateral value£711,000
50% LTV loan£355,500 available
Initial draw£355,000
Year 1 allocation from the £355,000 draw
Your income (12 × £5,000)£60,000
Loan interest (£355,000 × 10%)£35,500
Remaining in reserve pot£259,500
Why is the reserve pot so large in Year 1? Because BTC at £237,000 gives you a big initial draw (£355k), but your Year 1 costs are relatively modest (£95.5k). The surplus sits in the reserve pot, earning savings interest and acting as a buffer for future years when BTC growth may slow down or your inflation-linked income rises.
Worked Example — Year 2 (January 2029)
BTC has grown 15%
BTC price£272,550
Collateral value£817,650
New loan at 50% LTV£408,825
Previous loan balance£355,000
New draw (the growth)£53,825
Reserve pot for Year 2
Reserve from Year 1£259,500
+ Net savings interest (1.8%)+£4,671
+ New draw+£53,825
− Loan interest (£408,825 × 10%)−£40,883
− Income (£60,000 × 1.025)−£61,500
Reserve pot end of Year 2£215,613
The pattern repeats. Each year, BTC grows → loan refinances to 50% → new draw tops up the pot → interest and income come out. As long as BTC growth outpaces your rising costs, the reserve stays positive and the plan holds.
Reading the Dashboard Table
Each column in the year-by-year table on the dashboard maps directly to this cycle:
BTC Price
The projected Bitcoin price for that year, growing at your chosen annual rate from the start price.
Collateral
Your BTC holdings × that year's price. This is the total value backing your loan.
Loan Balance
Always exactly 50% of collateral. This is the total amount you owe. It grows each year as you refinance.
LTV %
Loan-to-value ratio. Should stay at 50% by design. Green means safe, amber means approaching limits.
Annual Income
Your inflation-linked income for the year. Starts at £60,000 (12 × £5,000) and rises 2.5% each year.
Interest Due
The annual cost of your loan (10% APR on the full balance). Paid from the reserve pot, not from your income.
Reserve Pot
Your buffer account balance after all inflows and outflows for the year. This is the number to watch — if it stays positive, the plan works.
New Draw
Fresh money from refinancing — the difference between this year's 50% LTV loan and last year's balance. This is what BTC growth gives you.
Status Indicators
The final column tells you how each year is doing:
FundedReserve pot has enough to cover at least one more year of income. You're comfortable.
TightReserve pot is still positive but has less than one year's income as buffer. The plan works, but there's no margin for error.
ShortfallReserve pot has gone negative. BTC growth hasn't kept pace with your income + interest costs. You'd need to reduce spending, sell some BTC, or find other income.
What You Can Change
Every input on the left panel recalculates the entire model instantly. Here's what each one does:
Monthly income neededYour target take-home per month — the whole plan is built around this number
Annual inflation %How fast your income rises each year to maintain purchasing power
Retirement yearsHow long the plan needs to last (25 or 30 years typically)
Start yearWhen the loan begins (default January 2028)
BTC heldHow many Bitcoin you pledge as collateral — "Use my BTC holdings" fills this from your portfolio
Start BTC priceProjected BTC price at the start year — "Use live BTC price" fills today's price
Default BTC growth %Sets the starting growth rate for every year — changing this resets all per-year rates
LTV %Loan-to-value target — 50% is conservative, lower is safer, higher is riskier
Loan interest rateThe APR charged on your Bitcoin-backed loan
Savings interest rateWhat the reserve pot earns while it sits in a savings account
Tax on savings interestYour marginal tax rate on savings interest (e.g. 40% for higher-rate taxpayers)
Year 1 loan drawThe initial lump sum — can be less than 50% LTV if you want a smaller starting loan
Per-Year BTC Growth — Scenario Planning
Real life doesn't deliver a smooth 15% every year. Bitcoin might crash 30% one year and rally 80% the next. The model lets you play with this.
In the year-by-year table, every row has an editable Growth % field. Change any single year's rate and the entire model recalculates instantly from that point forward — all downstream BTC prices, collateral values, draws, and reserve pot balances cascade accordingly.
Default growth (left panel)Changing this resets every per-year rate to the new value
Per-year growth (table)Override any individual year — highlighted in orange when edited
Negative growthEnter a negative number (e.g. −20) to model a crash — the input turns red
Reset defaultsThe "Reset defaults" button restores all years to the default rate
Try these scenarios: Set Year 3 to −40% (a deep bear market), then see how the reserve pot absorbs the shock. Or set years 5–8 to 30% (a strong bull run) and watch how the surplus builds. The model shows you exactly where the plan bends and where it breaks — so you can decide how much buffer you need.
End of Plan — Clear the Loan & Walk Away
The dashboard shows an exit summary with a year slider. Drag it to any year to answer the question: if I sold just enough Bitcoin to pay off the loan at this point, what would I leave behind for my children?
The calculation is straightforward:
1Work out how much BTC clears the loan
Divide the final loan balance by the final BTC price. For example, if the loan is £9.6M and BTC is £15.7M per coin, you'd need to sell about 0.61 BTC.
2Subtract from your stack
You started with 3 BTC. Selling 0.61 BTC leaves you with 2.39 BTC — roughly 80% of your original holdings still intact.
3Value what's left
Your remaining BTC at that year's price, plus any money left in the reserve pot, gives you your total pre-tax wealth. This is the number shown in the orange-bordered box on the dashboard.
Tax note. The BTC sale to clear the loan would be subject to Capital Gains Tax. The model shows the pre-tax figure — your actual take-home would depend on your CGT allowance, rate band, and any reliefs available at the time. This is one to discuss with a tax adviser.
The beauty of the model is that even after 30 years of drawing a comfortable inflation-linked income, a large portion of your original Bitcoin stack remains — because the loan was always funded by BTC appreciation, not by selling coins.
Key Assumptions
This is a projection, not a guarantee. Bitcoin may not grow at 15% every year — it could do much better or much worse. The model assumes steady compound growth for simplicity. In reality, you'd want to stress-test with lower growth rates (try 10% or even 5%) to see when the plan starts to strain. The loan interest rate could also change over time. Use the inputs to explore different scenarios and find the point where your plan breaks.
The model also assumes you can always refinance to 50% LTV each year without friction, which in practice depends on your lending platform's policies and Bitcoin market conditions.