Key facts: Lifetime mortgage interest compounds: at ~6.5%, a debt roughly doubles every 11 years. A £80,000 release at 65 can approach £160,000 by 76 and £320,000 by 87. Modern safeguards keep it controllable: no-negative-equity guarantees, optional interest payments, drawdown (interest only on what's taken) and inheritance protection.
Where the cost really lives
Set-up costs — arrangement, valuation, legal work, advice — are visible and modest. The engine is roll-up: no monthly payments means unpaid interest joins the balance and itself earns interest, silently, for as long as you live in the home. The result is exponential, and its scale depends on two things you partly control: the rate you fix, and — far more powerfully — how much you take, and when.
The worked example
A 65-year-old releases £80,000 from a £300,000 home at a fixed 6.5%, rolled up. Age 70: ~£110,000 owed. Age 76: ~£160,000 — the debt has doubled. Age 87: ~£320,000 — doubled again, now exceeding the home's original value (though house-price growth typically moves the other side of the ledger too). If the home appreciates at 2.5% annually it's worth ~£515,000 at 87: the estate keeps ~£195,000. Slower house growth or longer life squeezes that further — which is precisely what the no-negative-equity guarantee caps: the debt can never exceed the sale proceeds, whatever the arithmetic says.
The features that change the outcome
Drawdown is the big one: take £25,000 now and the rest only as needed, and compounding runs on a fraction of the money for years — routinely saving tens of thousands versus a day-one lump sum. Optional repayments (most modern plans allow ~10% a year penalty-free) can freeze or even reduce the balance — paying just the interest converts the product into, effectively, an interest-only loan. Inheritance protection ring-fences a percentage of the home's value at the cost of a smaller release. Together these turn "the debt doubles every 11 years" from destiny into a choice.
Costing it against the alternatives
The same need can often be met by downsizing (no interest at all), a retirement interest-only mortgage (income required, but no roll-up), or simply releasing less. Equity release wins when staying put matters and monthly payments don't fit — but it should win a comparison, not a default. Early repayment charges also deserve attention if your plans might change; fixed-ERC structures are the more predictable kind.
Running your own numbers
Regulated advice is mandatory for equity release — a specialist will project roll-up against your ages, rate and drawdown plan, with family in the room. Find an equity release adviser through Nesto — free, no obligation.
Frequently asked questions
How fast does equity release debt grow?
At the compound rate you fix — around 6.5% doubles the balance roughly every 11 years. Drawdown and voluntary payments slow it dramatically.
Can I owe more than my house is worth?
Not on Equity Release Council plans — the no-negative-equity guarantee caps the debt at sale proceeds.
Can I pay the interest to stop the roll-up?
Most modern plans allow voluntary payments (commonly up to 10%/year penalty-free) — paying the interest holds the balance flat.
Does equity release always wipe out inheritance?
No — house growth offsets roll-up, inheritance-protection features ring-fence value, and smaller/later releases leave more. It reduces estates; how much is largely a design choice.