How Long Does an iPhone Battery Last Before It Needs Replacing?

“Your battery is significantly degraded.” Nobody wants to see that message, usually appearing about eighteen months into ownership — right when you’ve stopped thinking of the phone as new. So how long does an iPhone battery last before it needs replacing, really? Apple’s official line and the real-world experience differ slightly, and knowing the difference saves you from replacing too early or suffering too long.

I’ve tracked battery health across half a dozen iPhones in my household. Here’s what the numbers actually look like.

How Long Does iPhone Battery Last: Apple’s Numbers vs Reality

Apple designs iPhone batteries to retain 80% of original capacity after 500 complete charge cycles (1,000 cycles for iPhone 15 and later, thanks to improved battery chemistry). A “cycle” is a full 0–100% discharge — so two days of 50% use equals one cycle.

In real-world terms:

• Heavy user (full charge daily): ~500 cycles in 16–18 months → noticeable degradation around the 1.5-year mark
• Average user (charge every 1.5 days): ~500 cycles in 2–2.5 years → degradation becomes annoying around year 2–3
• Light user (charge every 2+ days): 3–4 years before it matters
• iPhone 15 and newer: roughly double these figures — 1,000 cycles means 3+ years for most users before hitting 80%

That 80% figure is the key threshold: below it, Apple considers the battery “consumed,” iOS may throttle performance to prevent shutdowns, and you’ll feel the difference in daily use.

How to Check Your Battery Health

Settings > Battery > Battery Health & Charging. You’ll see:

• Maximum Capacity: the percentage of original capacity remaining. 100% is new; anything above 90% is healthy; 85–90% is ageing but fine; below 85% and you’ll notice; below 80% triggers Apple’s “Service” recommendation.
• Peak Performance Capability: if this says anything other than “Normal,” your phone has been throttling to cope with a weak battery.
• Cycle count (iPhone 15+: Settings > General > About): the raw number of cycles. Useful for confirming where you are against the 500/1,000 design target.
• 80% Limit / Optimised Charging: iPhone 15+ can cap charging at 80%, dramatically extending lifespan. Turn it on if you charge overnight — you don’t need 100% for a normal day.

Signs It’s Time for a Replacement (Beyond the Percentage)

• You’re charging twice a day with normal use
• The phone dies at 20–30% without warning
• It gets hot during light tasks (failing batteries generate excess heat)
• Apps stutter and the phone feels slow (performance throttling)
• It only works reliably when plugged in
• The back is bulging — stop using it immediately. A swollen battery is a fire risk; take it to Apple or a repair shop straight away, don’t put it in the bin.

UK Replacement Costs in 2026

• Apple Store (out of warranty): £75–£105 depending on model (£75 for SE/older, £95–£105 for recent Pro models)
• AppleCare+: Free if battery health is below 80%
• Independent repair shop: £40–£70 — fine for older models, but be aware non-genuine batteries trigger a “non-genuine part” warning and may affect battery health reporting
• DIY kits: £20–£40 — not recommended for most people; iPhone batteries are glued in and puncturing one is dangerous

The maths usually favours replacement over upgrade: £85 for a new battery buys 2+ more years on a phone that still does everything you need. Our guide on repairing vs replacing a cracked iPhone covers the broader decision, and if you’re considering going second-hand instead, read what to check before buying a used iPhone first.

Making Your Battery Last Longer

• Enable the 80% charge limit (iPhone 15+) or Optimised Charging (older) — the single biggest lifespan extender
• Avoid heat: don’t leave it on a sunny dashboard or under a pillow while charging; heat is batteries’ worst enemy
• Don’t stress about 0%: modern batteries handle occasional full discharges fine; it’s sustained heat and constant 100% that age them
• Update iOS: Apple regularly improves power management; staying current helps
• Check Apple’s official battery service pages for current pricing and the mail-in service option if there’s no Apple Store near you

iPhone Battery FAQs

Should I charge to 100% or stop at 80%?

For daily use, 80% is better for long-term battery health — lithium-ion batteries degrade faster when held at maximum charge, especially with heat. The 80% limit on iPhone 15+ automates this. Exception: charge to 100% before days you know you’ll need maximum runtime (travel, long events). Occasional full charges are harmless; constant 100% is what ages batteries.

Is wireless charging bad for the battery?

Slightly — wireless charging generates more heat than wired, and heat is the enemy. For overnight charging it’s fine (slow, cool enough), but fast wireless charging daily adds measurable wear over years. If battery longevity is your priority, wired charging (especially slow wired) is gentler.

Why does my battery drain faster in winter?

Cold temporarily reduces battery capacity — it’s chemistry, not damage. The phone may shut down at 20–30% in freezing weather and recover indoors. This is normal and doesn’t permanently harm the battery (though repeated extreme cold isn’t ideal). Keep the phone in an inside pocket on cold days.

Does dark mode save battery?

On OLED iPhones (X and later, except SE models), yes — measurably. OLED pixels turn off for black, so dark mode can save 10–30% depending on usage. On LCD iPhones (older models, SE), dark mode saves nothing — the backlight is always on regardless. Check which screen type you have before expecting miracles.

How do I know if an app is draining my battery?

Settings > Battery shows per-app consumption over the last 24 hours and 10 days. Look for background activity percentages — an app with high background drain that you rarely open is misbehaving. Restrict its background refresh (Settings > General > Background App Refresh) or delete it.

Is it worth replacing the battery on an old iPhone?

If the phone is otherwise fine and does everything you need: absolutely. £75–£105 at Apple buys 2+ more years. If the phone is also struggling with performance, missing iOS updates, or has other faults, put the money towards a newer model instead. The battery decision is really a phone-lifespan decision.

The Bottom Line

Expect 2–3 years of good battery life (3–4 on iPhone 15+), with 80% maximum capacity as the replacement threshold. A £75–£105 Apple battery replacement is almost always better value than upgrading a phone you’re otherwise happy with. Enable the 80% charge limit tonight, keep it cool, and your next battery will outlast this one. Batteries are consumables — replacing them is maintenance, not failure.