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Case Study: How the Johnsons Saved £11,400 Across Four Debts

A household with £28,000 in mixed debt used the avalanche method to destroy over £11K in interest.

7 min read Pro Article

Key Results

£11,423

Interest Destroyed

4.7 yrs

Timeline Shortened

The Johnson Family Profile

David (41) and Claire (39) Johnson, from Swindon, had accumulated debt across four accounts over seven years. Two children in primary school, one car, a rented three-bedroom house, and a combined household income of £3,400/month after tax. They were not reckless spenders. The car loan was necessary for David's commute. The credit card started as a way to spread Christmas costs. The store card offered 20% off a sofa they needed. The personal loan bridged a gap when Claire went part-time after their second child was born.

Every individual decision was reasonable. The total was not.

Debt	Balance	APR	Min. Payment	Monthly Interest
Store card (sofa + appliances)	£4,500	29.9%	£95	£112.13
Credit card (general spending)	£6,500	22.9%	£130	£124.04
Car loan (used Ford Focus)	£8,000	8.9%	£250	£59.33
Personal loan (income gap)	£9,000	6.5%	£105	£48.75
Total	£28,000	—	£580	£344.25

Of their £580/month in combined minimum payments, £344.25 — or 59.4% — was pure interest. Only £235.75 was reducing their actual balances. At that rate, debt-free date: September 2031. Total interest bill over the full term: £18,900.

"When we added it all up," Claire said, "I cried. Not because of the number — I knew it was big. But because we'd been paying £580 a month for years and it felt like nothing had changed. Now I understood why."

The Johnsons chose the avalanche method for the same reason Sarah did — the interest-rate gap between their debts was enormous. The store card at 29.9% was bleeding more than twice as fast per pound as the personal loan at 6.5%. Ignoring the highest rate would have cost them thousands.

Their plan:

Find £200/month in household savings
Direct the full £200 at the store card (29.9% — highest APR)
Pay minimums on everything else
When a debt is cleared, roll its minimum payment into the next target
Continue until all four debts are eliminated

The Johnsons did not take on extra work. They did not sell their car. They found £222/month through targeted household changes:

Change	Monthly Saving
Meal planning — reduced food shop from £520 to £360	£160
Renegotiated mobile contracts (x2 phones)	£22
Cancelled gym membership (neither partner used it)	£40
Total	£222

The meal planning made the biggest difference. Claire described the old groceries approach as "winging it" — shopping without a list, buying duplicates, and throwing away food that went off. She started planning seven dinners each Sunday, writing a precise shopping list, and buying only what was on it. The family ate the same food — just with zero waste.

"It didn't feel like sacrifice," Claire noted. "We were already wasting that money. We just didn't know it."

They rounded down to £200/month for comfort and kept £22 as a small buffer. The £200 was set up as an automatic standing order to the store card on payday, before discretionary spending could absorb it.

Phase 1: The Store Card Kill (Months 1–8)

The store card carried £4,500 at 29.9%. With £200 extra plus the £95 minimum, the Johnsons were striking it with £295/month while it bled £112/month in interest. Net principal reduction: ~£183/month.

By month 8, the store card was dead. Total interest paid during this phase: £672 (versus the £3,800+ it would have cost over its natural lifetime).

The moment it hit zero, David cut the card in half at the kitchen table while the children watched. "I wanted them to see it," he said. "They don't need to understand the maths yet, but they should see that debt is something you can kill."

Phase 2: The Credit Card Cascade (Months 9–18)

With the store card eliminated, its £95 minimum rolled into the credit card. The Johnsons' monthly strike: £200 + £95 + £130 = £425/month against the credit card at 22.9%. At that pace, the £6,500 balance (now slightly reduced by minimums during Phase 1) was cleared by month 18.

Phase 3: The Car Loan Sprint (Months 19–27)

With two debts eliminated, the avalanche was now rolling at £200 + £95 + £130 + £250 = £675/month into the car loan at 8.9%. The £8,000 balance (reduced to ~£5,500 by this point) was destroyed by month 27.

Phase 4: The Final Assault (Months 28–34)

Everything — £200 + £95 + £130 + £250 + £105 = £780/month — smashed into the personal loan at 6.5%. With interest at just £25/month on the remaining ~£4,200, nearly every penny reduced the balance. The personal loan was cleared by month 34.

Metric	Minimum Payments Only	With £200 Avalanche
Total interest paid	£18,900	£7,477
Interest saved	—	£11,423
Debt-free date	September 2031	January 2027
Years saved	—	4 years, 8 months
Monthly cashflow after debt-free	+£580	+£780

£11,423 in interest destroyed. 4.7 years of payments eliminated. £780/month freed. All from £200/month of spending they did not even notice losing.

The acceleration in later phases was dramatic because of how the avalanche works:

Month 1: £200 extra payment fighting 29.9% interest. Roughly 62% of each extra pound reduced principal.
Month 9: £425/month hitting a 22.9% card. About 71% hit principal.
Month 19: £675/month fighting 8.9% interest. About 93% hit principal.
Month 28: £780/month against 6.5%. 97% of every pound reduced the actual balance.

By systematically eliminating the highest-rate debts first, the Johnsons ensured that more money hit principal with each phase. The interest bleed dropped from £344/month to £240, then £95, then £25. The acceleration was not linear — it was exponential. The last debt fell faster than the first despite being the largest.

The Johnsons described the psychological journey in three words: "control changes everything." Before the plan, monthly arguments about money were routine. After month 3, when they could see the store card balance visibly dropping in DaysBack, the arguments stopped. They were not fighting each other any more — they were fighting the debt. Together.

The children noticed too. "Mum and Dad aren't stressed about money any more," their eldest said, unprompted, at dinner one evening around month 12. Claire described that moment as the most powerful motivation she experienced during the entire journey.

By month 34, the Johnsons were debt-free. They redirected their £780/month into an emergency fund (reached £1,000 in six weeks), then into a savings account for a family holiday — their first in four years, paid for with cash, not credit.

Research from the Money and Mental Health Policy Institute confirms what the Johnsons experienced: debt is a leading cause of relationship strain, and structured repayment plans significantly reduce conflict because both partners share a clear, measurable goal. When you are fighting debt together, you stop fighting each other.

The alternative timeline is sobering:

Minimum payments would have continued until September 2031 — over 9 years of monthly payments.
Total interest paid: £18,900 — equivalent to a reliable used car, a year of childcare, or two family holidays.
The daily interest bleed of £11.32 would have continued draining £344/month — money the family could never redirect, invest, or enjoy.
Psychological weight: 9 more years of debt-related stress, reduced financial flexibility, and the ever-present risk that one emergency would add to the pile.

The difference between acting and not acting was £11,423 in saved interest, 4.7 years of freedom, and a fundamental change in the family's relationship with money. The only cost was £200/month (primarily from food waste they were already throwing away) and 34 months of focused execution.

£28,000 of debt was terrifying. £200/month of extra payments was not. The total was paralysing; the action was manageable.
The real enemy was the £344/month in interest, not the £28,000 balance. Kill the interest bleed and the balance follows.
The avalanche methodology was decisive. By targeting 29.9% first, the Johnsons reduced their daily interest faster than any other ordering would have.
Meal planning was worth more than a pay rise. £160/month in food waste elimination was the single largest saving.
Tracking progress in DaysBack kept them going. Seeing "days deleted" climb every month turned a 34-month slog into a game they were winning.
The cascade was the secret weapon. Each eliminated debt freed up its minimum payment, which rolled into the next target. By Phase 4, the Johnsons were throwing £780/month at their final debt — 290% more than they started with.
Communication made it a team effort. David and Claire agreed on the plan together, celebrated kills together, and held each other accountable. Debt plans fail when one partner is not on board.

What Happened After Debt Freedom

Six months after clearing their final debt, the Johnsons had:

Built a £3,000 emergency fund (from the redirected £780/month, it took less than 4 months)
Taken a family holiday to Cornwall — paid in cash, no credit card, no BNPL. Cost: £850. "It felt like the most expensive holiday we'd ever had," Claire said, "because we actually paid for it. And it felt like the cheapest, because we had zero guilt."
Started pension contributions. David increased his workplace pension from 3% to 8%, and Claire opened a personal pension with £100/month.
Taught their children about money. The eldest now has a savings jar with three sections: Spend, Save, Give. "We didn't have that growing up," David said. "If we can break the cycle for them, the whole journey was worth it twice over."

The Johnsons' story is not exceptional. It is replicable. The numbers change, the debts change, the timelines change — but the principles do not: concentrate extra payments on the highest-rate debt, roll freed payments forward, track everything, and do not quit.

If your household has multiple debts, run them through the Overpayment Squeezer to see your version of the Johnsons' story. Even £50/month of extra payments will move your debt-free date forward.

For free, confidential family debt advice, contact StepChange (0800 138 1111) or Citizens Advice.