Short answer
How to check a heating engineer or HVAC contractor: Gas Safe and MCS in the UK, licences, load calculations and permits in the US and Canada, and warranties.
Heating and cooling jobs combine three risks: gas or refrigerant safety, a large bill, and equipment that will be in your home for many years. Getting the right installer matters more than getting the right brand. This guide covers boilers and heat pumps in the UK, and furnaces, air conditioning and heat pumps in the US and Canada.
UK: boilers and gas work
Gas Safe Register
Anyone doing gas work in your home in Great Britain, Northern Ireland, the Isle of Man or Guernsey must by law be on the Gas Safe Register. That includes fitting, moving, servicing or repairing a gas boiler, hob, fire or gas pipework. There is no grey area here, and a handyman who "knows gas" is not enough.
Check properly:
- Ask to see the Gas Safe ID card of the engineer who will actually do the work, not just the company owner. It carries a photo, a licence number and an expiry date.
- Turn the card over. The back lists the categories of gas work the engineer is qualified for, such as domestic boilers, cookers or fires. An engineer qualified for cookers is not automatically qualified for boilers.
- Check the number on the Gas Safe Register website or by phone with the Register, and confirm the categories match your job.
Oil boilers are a different trade; installers are commonly registered with OFTEC. Ask which scheme applies if you are not on mains gas.
Building Regulations notification
Installing a new boiler is notifiable work under the Building Regulations. A Gas Safe registered engineer can notify it through the Register, after which you should receive a Building Regulations compliance certificate in the post. If it does not arrive, ask the installer. You will want it when you sell the house.
Warranty registration and servicing
Manufacturer warranties on boilers usually depend on two things: the boiler being registered with the manufacturer after installation, and annual servicing by a Gas Safe engineer. Ask the installer whether they register the warranty for you, or whether you need to do it, and get the warranty terms in writing. Some longer warranties are only offered through approved installers.
The installer should also complete the commissioning checklist (often called the Benchmark checklist) in the boiler manual. Keep it with the manual.
Heat pumps
For air source and ground source heat pumps, look for an installer certified under the Microgeneration Certification Scheme (MCS). Government grants for heat pumps, such as the Boiler Upgrade Scheme in England and Wales, require an MCS certified installer, and the installer normally applies for the grant on your behalf. Ask how they calculated the heat loss of your home, what radiator changes they propose, and how the system will be set up to run efficiently. A heat pump quote that skips the heat loss survey is a weak quote.
US and Canada: furnaces, AC and heat pumps
Licences
HVAC licensing is set by states in the US, sometimes with extra local rules, and by provinces in Canada. Some states license HVAC contractors directly, others through a general or mechanical contractor licence. Technicians who handle refrigerant must also hold EPA refrigerant handling certification in the US. In Canada, gas fitting is licensed provincially; in Ontario, fuel safety is regulated by the Technical Standards and Safety Authority (TSSA). Check the licence on your state or provincial lookup rather than taking a number on a business card at face value.
Sizing: ask for a load calculation
Equipment that is too large short-cycles, wears faster and can leave a house humid; equipment that is too small cannot keep up on the coldest or hottest days. The standard method in North America is a room-by-room load calculation, commonly done to ACCA Manual J. Ask each contractor:
- Did you do a load calculation, and can I have a copy?
- How did you account for insulation, windows and air leakage?
- Will the existing ductwork suit the new equipment, and if not, what changes are included?
A contractor who sizes the new unit only by reading the label on the old one is guessing.
Permits and inspection
Replacing a furnace, boiler, air conditioner or heat pump usually needs a mechanical permit, and gas work may need a separate permit, followed by an inspection. Ask who pulls the permit and whether its cost is in the quote. Skipping the permit can cause problems with insurance, resale and some rebate programmes.
Comparing heating and cooling quotes
Quotes in this trade vary widely because they often describe different systems. Put them side by side and check:
- Exact make, model and capacity of each piece of equipment.
- What is included: removal and disposal of old equipment, flue, controls, thermostat, pipework, ductwork, electrical connections, condensate drain.
- Permits, notification and commissioning.
- Manufacturer warranty, and any separate labour warranty from the installer, with the terms written down.
- Who registers the warranty and what servicing it requires.
- Payment stages, and how much is due before the equipment is installed.
- Any grants, rebates or tax credits the contractor claims you qualify for, and who applies.
Be cautious with high-pressure sales visits that offer a discount only if you sign today. A real price will still be valid next week. For a step-by-step method, see getting quotes.
Repairs and servicing
For a breakdown, ask for the call-out or diagnostic charge up front and whether it is deducted from the repair. Ask for the faulty part to be named and, if it is replaced, to see the old one. If a technician says the whole system must be replaced, get a second opinion unless there is an immediate safety issue, such as a gas leak or a carbon monoxide risk, in which case follow the engineer's safety advice and the gas emergency service's instructions.
For servicing, ask what the service includes and get a written record each time. It supports your warranty and helps the next engineer.
Before you pay the final bill
- The system has been commissioned and demonstrated to you, including the controls.
- You have the manuals, commissioning record and warranty details.
- Notification or permit and inspection are done, or you know when the certificate will arrive.
- The old equipment has been removed if that was agreed.
For the paperwork to check on any trade, see how to vet a builder. If your job also needs pipework changes, our plumber guide covers what to ask.