Ideal Classic Boiler Review
Ideal's ground breaking combi boiler

Company type: Manufacturer

HQ: Hull, England

Founded: 1906

CEO: Shaun Edwards

First launched in 1991, the Ideal Classic boiler was the UK’s first cast-iron combination boiler and, due to its easy installation, reliability, and simple design, it quickly became a popular choice in households. Since then, the Classic has gone through upgrades to become a highly efficient boiler. Let’s find out if the latest version of the Classic should be held in the same high regard as its predecessor.

Ideal Logo

What Ideal Classic boilers are there?


The Ideal Classic boiler is a High Efficiency (HE) combination boiler that is available in the following power outputs:

Max. Hot Water Output Max. Central Heating Output
Ideal Classic 24 24.2kW 24kW
Ideal Classic 30 30.3kW 24kW
Ideal Classic 35 35.3kW 24kW

What is a High Efficiency combination boiler?

A combination (or combi) boiler is a combination of a water heater and a central heating boiler in a single unit. A combi boiler uses water from the mains water supply and produces hot water on demand, rather than storing it in a tank or cylinder like conventional (heat only) and system boilers. The lack of a need for a tank or a cylinder, which takes up space, makes combi boilers a popular choice for properties with limited space as they don’t need a hot water storage tank or cylinder.

A High efficiency combination boiler recovers heat that was previously expelled through the flue and directs it back into the heating system. This process means that HE boilers use less gas to heat your home, which could save you money on utility bills.

What does power output mean?

A boiler’s power output refers to how much power it uses to heat water or the central heating system. A boiler’s power output is often referred to as boiler size and is measured in kilowatts (kW).

Hot water output refers to the maximum amount of power a boiler will use to heat up water for a home. Similarly, central heating output refers to the maximum amount of power a boiler will use to heat up a property’s central heating system.

As a general rule of thumb, the more heat and hot water a property needs, the higher the boiler’s power output, or “size”, needs to be.

What other differences are there between each Ideal Classic boiler?

Other than the different hot water power output, the main difference between each Ideal Classic boiler is their flow rates:

Ideal Classic 24 9.9 litres per minute
Ideal Classic 30 12.4 litres per minute
Ideal Classic 35 14.5 litres per minute

A boiler’s flow rate refers to how much hot water the boiler can send to the hot water taps or showerhead in one minute. A good flow rate for a shower is between 10 and 15 litres per minute.

Essentially, the more hot water outlets used at the same time in a household, the higher the boiler flow rate will need to be.

How energy efficient are Ideal Classic boilers?


Ideal Classic boilers have an ErP (Energy-related Products) rating of A, making them at least 90% efficient.

ErP ratings are given to all products that consume energy, such as appliances like boilers, and are graded from A-G, with A-rated products being at least 90% efficient and G-rated products being below 70% efficient. Products with a higher ErP rating have better performance standards and produce lower greenhouse gas emissions.

The efficiency of a boiler is what percentage of its power output it uses to generate heat. Many old boilers use as little as 60% of their energy to heat up a property, which means they waste as much as 40% in the process. To put this into money terms, for every £1 spent on the boiler’s energy usage, only 60p would have gone into heating a home, while 40p would just be wasted!

Having a high efficient condensing combi like an Ideal Classic boiler could reduce a household’s carbon footprint and save homeowners money on their heating bills every year.

Ideal Classic key features

Compact cupboard fit

Ideal Classic boiler measures 700mm high, 395mm wide, and 285mm deep and weighs between 30.85 and 31.05kg. These dimensions mean that an Ideal Classic boiler can be classified as a compact boiler.

A compact boiler is a boiler that is small enough to fit into a standard kitchen cupboard.

The Ideal Classic boiler’s modest size makes it a good choice for properties with limited space.

Can be installed in colder areas of the property

If the water in an Ideal Classic boiler falls below 5 °C, the frost protection feature will activate and switch the boiler on to prevent the water from freezing.

If the water in a boiler freezes, the boiler is in danger of breaking down, which could cost hundreds of pounds in boiler repairs or possibly a boiler replacement, which could cost a few thousand pounds!

Due to its frost protection feature, homeowners can have peace of mind knowing that they can have an Ideal Classic boiler installed in colder parts of their property, such as the garage or the loft, without running the risk of the water freezing.

Avoid unexpected costs.

With a Smart Plan cover policy, you can rest easy knowing if there's an issue with your boiler, we'll usually have you back up and running within 48 hours.

OR Find out more

Increase efficiency and save money with Ideal weather compensation feature

When an Ideal Classic boiler is fitted with the weather compensation feature, it increases its efficiency and, as a result, could save the homeowner money on their energy bills.

Weather compensation is an energy saving feature that measures the outside temperature and sends a signal to the boiler, which adjusts its power output or water flow in response. For example, if it is warm outside, less heat will be needed to keep the rooms at the desired temperature, so the boiler will reduce its water flow to reach the ideal temperature for your household.

This innovative feature helps to keep the temperature consistent throughout your home, increases the boiler’s efficiency, and could lead to savings on your energy bills.

Is an Ideal Classic boiler suitable for my home?

Ideal Classic boilers are available with hot water outputs of 24kW, 30kW and 35kW.

Below is a rough guide to which Ideal Classic boiler model is best suited to a property, based on its power output.

Property Type Suitable Ideal combi boiler
  • 1-2 bedrooms
  • 1 bathroom
  • Fewer than 5 radiators
  • Ideal Classic 24
Small house
  • 1-2 bedrooms
  • 1 bathroom
  • 5-7 radiators
  • Ideal Classic 24
Medium house
  • 2-3 bedrooms
  • 1 bathroom
  • 6-7 radiators
  • Ideal Classic 30
Family house
  • 3-4 bedrooms
  • 1 bathroom
  • 1 ensuite
  • Up to 10 radiators
  • Ideal Classic 35
Large family house
  • 4-5 bedrooms
  • 2 bathroom
  • 1 ensuite
  • Up to 15 radiators
  • N/A

Get the right boiler size for your home

When it comes to boiler size, bigger isn't always better. If the boiler’s power output is too high, then you may end up paying more money on your energy bills as the boiler may use more power than necessary. On the other hand, if the boiler is too small, it may find it difficult to meet your property’s heat and hot water demands. This is why it is so important to get the right size boiler for your property.

At Smart-Plan, we have Gas Safe registered engineers who will assess your property and heating demands and determine the right size boiler for you.

Does your home have high hot water demands?

Although Ideal Classic boilers come in a range of different power outputs to suit a number of different sized properties, they are not the best choice for larger properties with very high hot water demands. As with all combi boilers, Ideal Classic boilers heat water on demand, and if the demand is too high, the flow rate to each water outlet will be reduced considerably.

If you have high hot water demands, then a conventional or system boiler may be a better choice for you as they store large amounts of hot water in a tank or cylinder for later use.

How long is the warranty on an Ideal Classic boiler?

Ideal Classic boilers come with Ideal’s lowest extended warranty duration of 2 years.

As standard, a boiler will have at least a 1 year warranty, but often manufacturers offer extended warranties to give customers added peace of mind.

If your Ideal Classic boiler has a mechanical or electrical breakdown due to its materials or installation, then your Ideal warranty will provide you with full parts and labour repair services or a replacement boiler, free of charge, subject to the terms and conditions.

If you would like to find more information on Ideal’s warranties, click here.

Give your boiler a service.

Make sure you don't invalidate your warranty. Call Smart Plan to get a boiler checkup to see if everything is in good working order.

OR 020 8146 3960

Ideal Classic boiler Specifications

Ideal Classic 24 Ideal Classic 30 Ideal Classic 35
Width 395mm 395mm 395mm
Height 700mm 700mm 700mm
Depth 285mm 285mm 285mm
Weight 30.85kg 30.95kg 31.05kg
Fuel Type Gas Gas Gas
Energy Rating (Heating) A A A
Energy Rating (Water) A A A
Flow Rate 9.9 l/min 12.4 l/min 14.5 l/min
Central Heating Max. Output 24 kW 24 kW 24 kW
Hot Water Max Output 24.2 kW 30.3 kW 35.3 kW
Sound Power Level 45 dB 46 dB 44 dB
Warranty 2 years 2 years 2 years

Still need help with your Ideal boiler?

Call Smart Plan and speak to our expert engineering team free of charge.

0333 772 6247