The 50% Rule: How to Decide Whether to Repair or Replace Anything

Published 14 March 2026 · 8 min read · By Mend or End

Every homeowner faces the same dilemma eventually: your appliance breaks down, the repair quote arrives, and you're left wondering whether it's worth fixing or whether you should just buy a new one. The decision feels complicated, but there's a surprisingly simple rule that consumer organisations and repair professionals alike have relied on for decades — the 50% rule.

In this guide, we'll explain exactly what the 50% rule is, why it works, how to apply it to common UK appliances and items, and when you should consider modifying it based on age and other factors.

What is the 50% Rule?

The 50% rule is simple: if the cost of repairing an item exceeds 50% of the cost of replacing it with a new equivalent, you should replace it. If the repair costs less than 50% of a replacement, it's generally worth repairing.

The logic is intuitive: if you're spending half the price of a new item to fix an old one, you're getting a poor deal. The repaired item still has an older body, worn components, and no warranty — yet you've paid significantly for the privilege of keeping it. At that cost level, a new item with a full manufacturer's warranty and improved energy efficiency almost always represents better value.

The 50% rule has been endorsed by consumer organisations including Which? and the Energy Saving Trust, and is widely used by appliance repair professionals when advising customers on whether to proceed with a repair. It's not a hard scientific formula, but it captures real-world economics in a way that's quick to apply.

Why the 50% Rule Works

The rule works for several practical reasons. First, it sidesteps the sunk cost fallacy — the very human tendency to throw good money after bad because you've already invested in something. "But I've already paid £300 in repairs this year" is not a good reason to spend another £400. The 50% rule focuses on future value, not past expenditure.

Second, the rule implicitly accounts for remaining useful lifespan. A repair that costs 30% of replacement value is clearly worth doing if the item will then last another 5–7 years. But as repair costs creep toward the 50% threshold, you need to be increasingly confident the item will last long enough to justify the investment — and with older appliances, that confidence is harder to justify.

Third, it creates a clear decision boundary. Without a rule like this, the decision becomes emotionally clouded. The 50% rule removes ambiguity and gives you a defensible, rational answer you can act on quickly.

The 50% Rule Applied to Common UK Items

Here's how the 50% rule plays out across the most common items UK households repair or replace. Replacement costs are typical mid-range values for 2026:

Notice how the same rule produces different answers depending on the relative costs. TV screen repairs often cost more than 50% of a new TV — especially budget models — which is why it rarely makes financial sense to repair a TV screen. By contrast, most phone screen repairs on mid-to-high-end devices fall comfortably below the 50% threshold.

When the 50% Rule Isn't Enough

The 50% rule is an excellent starting point, but it doesn't capture everything. There are situations where you should adjust your decision based on additional factors:

Age of the item: The 50% rule assumes the item, once repaired, has a reasonable amount of useful life remaining. If you're repairing a 12-year-old boiler at 45% of replacement cost, you might technically pass the 50% test — but with only 1–3 years of life remaining, the economics are questionable. Age matters enormously.

Recurring faults: If an item has been repaired multiple times already, each repair is less likely to be the last one. A washing machine that's had three separate repairs in two years is showing systemic wear. Even if the latest repair quote passes the 50% test, the cumulative spend is what matters.

Energy efficiency: Older appliances — particularly boilers, washing machines, and dishwashers — often have significantly lower efficiency ratings than their modern counterparts. A 15-year-old boiler running at 75% efficiency versus a new A-rated boiler at 93% can mean £200–£400 more in energy bills each year. Over 5 years, that's £1,000–£2,000 extra — which changes the economics of the repair decision substantially.

Emotional or practical value: The 50% rule is a financial tool, not a moral one. If an item has sentimental value, is difficult to replace (a rare model, a specialist tool), or serves a purpose that a new equivalent wouldn't replicate, it's perfectly rational to invest more in repair than the rule would normally recommend.

The Modified 50% Rule — Adding the Age Factor

A more nuanced version of the 50% rule adjusts the threshold based on how far through its expected lifespan an item is. The idea is simple: the older an item, the lower the percentage of replacement cost you should be willing to spend on a repair, because the remaining useful life is shorter.

• New to mid-life (0–40% of expected lifespan): Apply the standard 50% rule — repair if it costs less than half of replacement.
• Mid-life (40–70% of expected lifespan): Apply a 40% threshold — only repair if the cost is under 40% of replacement.
• Late life (70–100% of expected lifespan): Apply a 25–30% threshold — only minor, cheap repairs are justified.

For example: a washing machine with a 10-year expected lifespan that's 8 years old is at 80% of its lifespan. Using the modified rule, you'd apply a 25–30% threshold. If it costs £400 to replace, you'd only repair it for £100–£120 or less — not the full £200 the standard 50% rule would allow.

This modified approach more accurately reflects the real-world economics of ageing appliances and helps avoid the scenario where you spend £180 repairing something that fails again three months later.