Fuel and insurance are the costs people budget for, and depreciation is usually larger than both combined.
The first year
New vehicles lose a substantial proportion of value in the first twelve months.
Which is the single largest year of loss for almost every model.
The curve
Loss slows considerably after the first few years.
Which is why buying at two to three years old changes the ownership economics substantially.
What affects the rate
Brand reputation, reliability record, fuel type and how many were built.
Which is why identical-looking cars depreciate very differently.
Why the first year is worst
The transition from new to used removes a category of buyer.
Which is a step change rather than gradual wear.
Registration alone accounts for a meaningful part of it.
Mileage effects
Higher mileage reduces value at a decreasing rate.
Which means the first tens of thousands cost more than later ones.
Specification and colour
Options rarely return their cost at resale.
Which is worth knowing when configuring a new vehicle.
Unusual colours narrow the buyer pool and lengthen the sale.
Market shifts
Fuel prices, regulation and changing tastes.
Which have repeatedly moved residual values faster than anyone forecast.
The practical implication
Buying slightly used and holding longer avoids the steepest part of the curve entirely.
Measuring it
Retained value as a percentage after a set period.
Which is published by valuation firms and varies by market.
Three-year retained value is the conventional comparison point.
Which vehicles hold value
Strong reliability records, controlled supply and consistent demand.
Which is a short list in any given market.
Heavily discounted new cars depreciate from the discounted price, not the list price.
Condition and history
Documented maintenance, clean bodywork and matching interior.
Which affects the final few percent rather than the shape of the curve.
Selling method
Private sale, dealer part exchange and online buying services.
Which produce different prices for the same vehicle.
The spread is frequently larger than a year of depreciation.
The practical takeaway
Depreciation is a cost you can partly choose through what and when you buy.
Why it is the largest cost
A vehicle bought new and sold after three years typically loses a substantial share of its value.
Which over that period usually exceeds total spending on fuel, insurance and servicing combined.
Because it arrives as a lower sale price rather than as a bill, it does not feel like spending.
Fleet and rental supply
Large volumes returning to the market at predictable points.
Which suppresses used values for affected models.
This is why some models depreciate far faster than their quality would suggest.
Regulatory effects
Emissions zones, fuel duties and future sale restrictions.
Which have moved residual values for particular fuel types sharply.
Diesel values in several European markets are the clearest recent example.
Electric vehicle residuals
Falling new prices and improving specifications.
Which has pushed used values down faster than forecast.
Reducing your exposure
Buy used, hold longer, choose models with a record of retaining value, and sell privately where practical.
Timing a purchase
Model year changes, facelifts and end-of-line runs.
Which produce predictable dips in used values.
Buying just after a facelift means buying the older-looking version cheaply.
Nearly new
Pre-registered and ex-demonstrator vehicles.
Which have absorbed the first drop and are effectively new.
These are consistently among the better-value purchases available.
Long ownership
Keeping a vehicle beyond the point where depreciation flattens.
Which is the cheapest way to run a car and requires accepting an older vehicle.
Maintenance costs rise as depreciation falls, and the total usually still favours keeping it.
Tracking your own vehicle
Checking current trade and retail values annually.
Which informs the decision of when to change.
What to check before buying
Published three-year retained value figures for the models on your shortlist.
Which are available from valuation firms and motoring publications.
A difference of ten percentage points over three years is a substantial sum on a mid-priced vehicle.
The summary
Depreciation is the largest cost of new car ownership, it falls steeply then flattens, and the two decisions that affect it most are what you buy and how long you keep it.
Neither requires any expertise beyond looking the numbers up before committing.
A general note on sources
Figures in this area come from manufacturer publications, regulator test programmes, insurance claims data and independent consumer testing, and those four sources do not always agree.
Where they conflict, the independent testing and the real-world claims data are usually the more reliable guide, because manufacturer figures are produced under conditions chosen by the manufacturer.
Anything specific to your own vehicle should be checked against its handbook and against a qualified technician familiar with the model, since specifications differ between markets and between production years in ways that general articles cannot capture.
One last practical point
Almost everything above becomes easier if you keep a simple record for your own vehicle: what was done, when, at what mileage and by whom.
It takes a folder and about five minutes a year, and it improves resale value, makes warranty claims straightforward and turns vague worries about condition into questions you can actually answer.
Owners who do this rarely get caught out, and owners who do not almost always wish they had started earlier.