It depends on a lot of different factors, batteries lose capacity as they age and do more cycles, what you see as 'range' also depends on how the battery is managed and how you drive the car.
If you are driving the same route at the same time in similar conditions at the same speed and the range has dropped by a 3rd then you may have a problem. if you are now driving at high speeds then a drop from 21 to 14 miles is not unreasonable. Range is highly dependant on driving style and is difficult to predict with any acuracy.

 

Thank you all. I am more concerned that the battery no longer charges up to 21 miles, but now caps out at only 14. My commute to and from work is approx 16 miles driving surface streets. So if I can only charge 14 miles I run out of e- power sooner now.

 

Let's not forget it's a PHEV. By their very nature (and assuming they are used correctly, i.e. always charge the battery when you can and drive as many km in EV mode only), they will be more prone to degradation than an EV (more cycles). So once a PHEV battery reaches 80% degradation, the range will start diminishing in a notable manner.

A 5 year old car could easily have 2000 cycles on the battery. For an NCM battery that is quite a lot, even more so in a PHEV use case so I would not be surprised if that battery is reaching the knee point.

 

Let's not forget it's a PHEV. By their very nature (and assuming they are used correctly, i.e. always charge the battery when you can and drive as many km in EV mode only), they will be more prone to degradation than an EV

Plus of course, they are virtually always charged to 100%. My 2016 PHEV is now down to 70% SOH but still gives me about 16 miles on battery. As the car always keeps a 30% buffer before starting the engine, that is effectively 40% instead of 70% when new.

 

I drive a 2018 530e, 80k miles, I’ve consistently managed 20 miles in summer months and around around 10-15 in winter depending on heater use. If you’re driving with zero aircon and taking it easy on speed/acceleration then I’d say you have an issue.
GF

 

Many PHEVs are sold with 5-8 year battery warranties - it may be worth investigating if this warranty covers capacity degradation.

 

I’m pretty sure the 530e is £60k miles, not ideal at all!

 

The confusion caused by charging being stated in miles keeps coming up. When you fill a petrol car you fill with litres or gallons not miles and the same with EVs, except here it's called kWh. How far you go on your litre / gallon / kWh is down to the driver. The difference is the tank size of the ev or phev slowly decreases ovr time.

Once the phev is at 0 battery miles remaining ie the battery is empty then charge and note the kWh used. Compare to the number of kWh used when new to fully charge. Any change is a shrinkage of capacity. A sudden drop-off in capacity is a symptom of battery failure maybe a faulty cell. Gradual capacity reduction is expected.
Edit I believe the original capacity charging from 0 to 100% was 11kWh. Check what it is now, your chargepoint should have the info after the car is charged.