2023’s Best Oil Boilers [And A Complete Buyer’s Guide]
Considering a new oil boiler, and don’t know where to start? 
Good news — our 5-minute review of the best oil boiler models covers everything you need to know.
Here, we’ll cover the best oil boiler brands and help you size your appliance. We’ll also discuss warranties, price and even the cost of installation.
Sizing an Oil Boiler
Before reading this 5-minute review, bear in mind that different properties (even ones of the same size) may have differing demands for heating and hot water.
Choosing the wrong boiler size will mean one of two things:
- You’ve purchased a boiler that’s too big, and paid more than you should have.
- Your oil boiler ISN’T powerful enough, so it struggles to keep up with your central heating system and hot water demand.
Since you need an OFTEC-registered heating engineer to install an oil boiler, you should ask your engineer to survey your property and recommend a boiler size. You can get multiple quotes and advice from them here.
Types of Oil-Fired Boilers
When choosing a boiler, it’s not just the brand you need to consider.
Certain heating systems REQUIRE a specific type of boiler. Here are the 3 most common boiler types:
Combi Oil Boilers
An oil combi boiler doesn’t require a hot water storage tank, cylinder, or a cold-water tank. It heats water on demand.
The benefit here is that not having these water storage facilities is a HUGE space saver.
On the flip-side, oil combi boilers are only suitable for properties that don’t have high heating/hot-water demand (i.e. only one shower operating at once).
Regular Oil Boilers
A regular oil boiler (sometimes called a heat-only boiler, or a conventional boiler) fills up a large hot water storage tank, which makes it suitable for heating systems with robust hot water demand.
A regular boiler setup also requires a cold-water storage tank, which is usually fitted in your loft.
System Oil Boilers
System boilers work just like regular oil boilers — they just don’t require a cold storage tank in the loft. And whilst this doesn’t translate to a reduction in installation cost, it means one less thing to repair in the future.
If you live in a 4-5+ bedroom property and want to use 2+ showers at once, it’s advisable to go for a system oil boiler over its regular counterpart.
Best Oil Boiler Brands to Look Out for in 2024
There are a tonne of brands offering boilers, but finding the best oil boiler is no simple task. The problem? Most of them are mediocre quality, and over-priced.
At my time working in a plumbing merchant, most oil boilers were on an “order-in” basis. And, for the life of me, I can only remember ordering from three oil boiler brands.
That’s not to say there aren’t other brands out there that are high quality. It’s just confirmation that homeowners like you, and registered OFTEC oil boiler engineers, like these three brands more than any other.
3 Best Oil Boiler Brands in 2024
If I was upgrading my oil boiler, I’d only stick to the three brands below.
Warmflow Oil Boiler
Warmflow oil boilers are the most efficient on the market. That’s not opinion; that’s fact!
You’ll see plenty of manufacturers advertising their “A-rated” oil boilers. The problem? A-ratings are split between AA (the best) and A (the second best).
Warmflow produces the only AA-rated oil boiler in the UK & Ireland.
This means that AA-rated Warmflow oil boilers are up to 30% more efficient for hot water than A-rated oil boilers. And that translates to a noticeable drop in energy bills, as well as doing your bit for the environment!
But, there’s something else we like about Warmflow. A brand’s boilers are only as good as the parts they use. And, the brands Warmflow uses for components are ones we know and love. This is what separates an oil boiler brand making this “top” list from being a cheap “no-name” brand.
Across their range, Warmflow use well known branded components such as:
- Riello burners
- Honeywell diverter valves
- Grundfos pumps
We like 🙂
Warranty
So, Warmflow are the most efficient boilers on the market. But how does their warranty fair against leading brands? 
Well, it’s long. The warranty on their Titanium, for instance, is 5-years. That compares to some Worcester Bosch oil boilers that only come with a standard of 2 years.
Another note here is that Warmflow offer an “out-of-the-box” 5-year warranty. As long as it’s installed by qualified oil boiler heating engineers, that warranty is valid.
And that might seem normal, but it’s not. Other brands (Grant, for instance), only honour their 5-year warranty when the boiler is installed by their accredited heating engineers; you’ve been warned!
Warmflow Oil Boiler Range
And, Warmflow have an oil boiler to suit every property that’s located off the grid.
U-Series
The U-Series is modern and stylish. It’s designed as an internal unit, fitting most kitchen and utility applications. And, the fact it’s easily accessible helps to reduce oil boiler service costs.
K-Series
Struggling to find space in your property? That’s where the K-Series comes into play; it’s Warmflow’s external oil boiler.
They’re quick and easy to install (reducing installation costs), and are fully insulated from the elements. If you need a boiler fitted externally; the K-Series is for you.
B-Series
The B-Series has been designed for indoor installation, in areas such as boiler houses and garages. It’s got a highly efficient heat exchanger, and like the U-Series, easy access means reduced servicing time (and costs).
But it doesn’t stop there. Unlike cheap oil boilers, Warmflow have gone all out with the B-Series. They’ve fitted a Riello burner (the best in the business), meaning it’s not just efficient, but quiet too.
Grant Oil Boilers
Grant offer some of the best oil boilers for home heating. No surprise there — they’re an oil boiler specialist. 
They absolutely kill it with their Grant Vortex and VortexBlue, which boast ridiculously high energy efficiency levels (up to 93.3%) gross.
Warranty
Their bragging rights don’t stop there.
When investing this amount of cash in your property with a new boiler, you want to make sure your back is covered with a long warranty. Many of the cheap oil boiler brands offer little in terms of warranty (1-year) or no warranty AT ALL!
No, thanks.
Grant oil boilers, like the Vortex and VortexBlue, come with a huge 5-year warranty — when installed by an accredited engineer.
Oil Boiler Range
Due to Grant’s extensive range, it’s not a case of finding the “most” suitable oil boiler for your property. Their range is so vast, your oil boiler engineer will be able to pinpoint the EXACT boiler for your home. The range includes:
VortexBlue
- Internal
- External
- Combi
Vortex Eco
- Utility
- External
- Wall Hung (Internal)
- Wall Hung (External)
Vortex Pro
- Utility
- External
- Internal Comi
Worcester Bosch Oil Boilers
Worcester Bosch need little introduction. They’re the most popular brand manufacturing combi gas boiler models, and they’re just as popular in the oil boiler market.
Warranty
Worcester Bosch oil boiler’s warranty starts at 2 years. Confirm with your engineer the exact warranty term for the model you’re installing.
Typically, Worcester will increase a warranty up to 5 years during promotional periods, and when the boiler is fitted alongside other Worcester branded products (heating controls and boiler filters, for instance).
Oil Boiler Range
Like Grant, Worcester Bosch oil boilers come in all shapes and sizes. It’s definitely worth speaking to an OFTEC registered oil boiler engineer before deciding on an exact Worcester boiler model. They’ll be able to recommend the most suitable Worcester oil boiler for your property.
You’ll have their two ranges from which to choose:
- Worcester Bosch Greenstar Danesmoor
- Worcester Bosch Greenstar Heatslave II
And, you’ll be able to install them externally or internally.
Like with Grant, you’ll be able to choose a boiler that’s a straight swap for your existing appliance in terms of kW output. However, you can also choose between combi, system, and regular boiler types.
Warmflow, Grant, or Worcester Bosch?
There’s no definitive way to pick the best oil boiler brand out of these three industry titans. Some installers (and homeowners) will prefer one brand over the other.
We’d be happy to fit any of the top 3 oil brands on our list. However, if you’re going for all-out warranty, efficiency, and therefore the best value for money, then Warmflow is a solid pick.
Oil Boiler Installation Costs
Oil boiler installation costs vary considerably. The variation in price (depending on kw output and type of boiler) varies much more than it does with gas boilers. Typical purchases costs can be £1,200-2,000 with installation in the £1,200-2,200 range.
There’s more details on oil boiler installation costs here.
Oil Boiler Installers
To install a gas or LPG boiler, fitters need to be registered with Gas Safe.
That’s not the case with oil boilers. Fitters need to be registered with the OFTEC (Oil Firing Technical Association).
OFTEC are responsible for managing over 8,000 trade professionals in the UK. If your oil boiler installer isn’t registered with OFTEC, they’re not qualified to fit your boiler.
What’s Next?
Thanks for reading our 5-minute review of the best oil boiler models in 2024, as well as the top brands, installation costs, and the types of boilers you can install on your property.
Still got questions about oil boilers? Leave a comment below and we’ll do our best to help you out.