What sets an auto repair shop's insurance cost
A shop's premium is not one price. It is four policies on four different meters: workers compensation on payroll, general liability on payroll or receipts, property on the values you declare, and the auto and custody side on what you drive and what you hold. There are no dollar figures on this page, because no published range names its methodology. Every input behind the figure you will be quoted is here instead.
Garage liability vs garage keepersFour policies, four meters
The single number on a proposal is a total. Underneath it, each line is measured against something different, and knowing which meter a line runs on tells you which answers you gave changed the price.
Workers compensation runs on payroll. The Texas Department of Insurance describes the arithmetic on its own rate guide: an employer is assigned one or more classifications by type of business, each employee's payroll is assigned to the appropriate classification, and the payroll in each classification is multiplied by the rate for that classification per $100 of payroll (Texas Department of Insurance, workers compensation rate guide). General liability runs on payroll or on gross receipts depending on the classification, which is why an insurer asks for last year's sales and this year's estimate (IRMI, payroll). Property runs on the values you put on the schedule, building and contents both, and a shop's contents are lifts, alignment racks, diagnostic equipment, and a parts inventory rather than desks. The vehicle and custody side is its own conversation and it is the one most specific to this trade, covered further down.
The classification is the first number, and it follows the work
Before any rate is applied, the rating system has to decide what kind of business you are. That decision is the largest lever on a workers compensation premium and a large one on general liability, and it is made on the work performed rather than the sign over the door. Brakes and oil changes, collision and refinish, glass, tires, and mobile service calls are all "auto repair" in conversation and are not one category to a rater.
Two consequences for a shop owner. The first: adding a service line can move you into a different classification, and finding that out at renewal is worse than raising it when you add the line. The second: if the classification on your declarations page does not describe your work, that is worth arguing before binding rather than at the audit, when the money has already been spent. Class codes are assigned under rules published by a state's rating bureau, and the bureau's wording is what an argument is settled against.
Shop type is where the differences show up in coverage as well as price. The paint booth, refinish, and structural work that separate a body shop are on auto body shop insurance; the working set for a general repair operation is on auto repair shop insurance; and a shop with no premises at all is rated on a different picture again, which is the subject of mobile mechanic insurance.
The number you pay at binding is a deposit, not the price
This surprises shop owners more than anything else on the bill. IRMI defines a premium audit as an audit of the exposure base after the policy period ends, to determine actual exposure and make a final calculation of premium (IRMI, premium audit). The standard general liability form says it about itself, in the premium condition: the premium shown as advance premium is a deposit premium only, and at the close of each audit period the insurer computes the earned premium for that period (ISO CG 00 01 specimen, New York OGS). A deposit premium is exactly that: an estimate collected up front against a figure nobody can know yet (IRMI, deposit premium).
Practically, this means a busy year bills you for the growth. A shop that estimated payroll for four technicians and finished the year with six will see the difference on the audit. It also means the estimate you give at binding is not a place to be optimistic in either direction: too low and the audit collects it later, too high and you have financed the insurer for a year.
Your loss history rides along: the experience modifier
Once a shop has been insured long enough to have a record, the record itself becomes a multiplier. IRMI defines the experience modifier as a factor developed by measuring the difference between an insured's actual past experience and the expected or actual experience of its class, applied as a credit or a debit against standard premium (IRMI, experience modifier). Average experience for the class is 1.0 and pays the manual premium. Worse than average produces a factor above it, better than average produces one below, and Texas names the same mechanism in its own description of workers compensation pricing (TDI, workers compensation rate guide).
The practical reading: a lift accident or a rash of small strain claims is not a one year event on the bill. It follows the shop into the years after it, which is the argument for treating a modest claim as a decision rather than a reflex.
What moves a repair shop's quote more than its floor plan
Customer vehicles are the exposure that makes this trade different, and they are priced separately from everything above. Garagekeepers offers three causes of loss, each selected and rated on its own: the comprehensive option, specified causes of loss (fire, lightning, explosion, theft, mischief or vandalism), and collision. The deductible structure differs between them, with a per-event maximum available on the first two and the collision deductible applying per auto (RNC-Pro, CA 99 37 garagekeepers analysis). On top of that sits the basis: legal liability by default, or one of the direct options, which drop the requirement that you be legally at fault before the customer's car is paid for. Direct primary responds before other available coverage and costs more than direct excess (IRMI, garagekeepers extra legal liability). Three separate choices, all of them yours, all of them on the price. The coverage itself is taken apart on garage keepers insurance, and which of the two coverages a shop needs is settled on garage liability vs garage keepers.
Four more things a shop does that change the picture. Towing customer vehicles in: ISO's commercial auto program defines towing operations as attending, servicing, or repairing a customer's auto where it became disabled, including transporting it from there to the repair garage (IRMI, towing operations), and how your policy treats the vehicle while it is on the hook is a question to ask by name. Loaner cars, which put your customer in your vehicle on a public road. Overnight storage, which decides the limit you need rather than the rate you pay. And hot work, welding, and refinishing, which change both the property and the liability side.
One structural note that reaches the price without appearing on it. ISO stopped supporting the garage coverage form for non-dealer service risks in its 2013 revision, and standard carriers moved repair shops to a general liability policy plus a business auto policy with garagekeepers added by endorsement, while dealers went to the auto dealers form (RNC-Pro, ISO auto dealers coverage form overview). Two quotes for the same shop can therefore be built out of different paper. Comparing them on the bottom line alone compares two things that are not the same product, which is what what garage insurance costs works through.
No state license sets the floor for a repair shop
Dealers are told what to carry. Repair shops usually are not, and Texas is a clean example: the Department of Licensing and Regulation runs a towing and vehicle storage facility program and lists no license for auto repair (TDLR), so what governs a Texas shop is the Deceptive Trade Practices Act rather than a coverage condition. The Attorney General's car repair page names the conduct: it is illegal to knowingly make a false or misleading statement about the need for parts, replacement, or repair service (Texas Attorney General, Car Repair Tips).
Which is the point worth carrying into a quote conversation. Nobody is going to hand a shop a required limit, so the limits are chosen against the exposure: the value of the cars on the lot on the busiest night of the year, the lease you signed, and the size of the claim a bad repair can produce after the vehicle leaves. Dealers work from the other direction, and their license conditions are on garage liability requirements.
When the inputs are assembled, the conversation to have is with an agent who writes garage business regularly and can say which form your quote is built on. Start at the overview if you want the coverage map first.