Choosing the right boiler

a quick guide by Chris O’Keefe

We all know our heating system is the heart of our home. Without heating and hot water in our homes (especially in the cold months) we wouldn’t survive, but it’s difficult to know what size, type, brand etc. to choose - and hard to find impartial advice!

Installing a new boiler is a large (but necessary) investment and not something we do every week (hopefully!), so it’s important to make the right choices. We’ve made this guide to help answer some of the many questions that will arise when you’re pondering on a choice of new boiler.

What type of boiler do I need?

Combination Boilers.

Commonly known as Combi boilers, these are often the first port of call most people make, because they don’t require a separate hot water storage cylinder. Combi boilers are generally more suited to smaller properties (one to two bathrooms) with a lower hot water demand but won’t be suited to all properties. It largely depends if your mains water supply is sufficient to cope with a combi boiler.

System Boilers and Regular Boilers.

Both these types of boilers use a hot water storage cylinder to heat your hot water and are perfectly suited to larger properties or properties with a high hot water demand due to the number of occupants.

What size boiler do I need?

An oversized boiler will have a negative impact on efficiency and more importantly on your fuel bill. While an undersized boiler won’t be able to cope with the demand you put on it and will always underperform.

The following are key points you should be discussing with your installer when getting quotes for a new boiler.

  • Number of radiators?
  • Number of regular occupants?
  • Number of baths, showers etc
  • Size of building
  • How well insulated your property is?
  • Where in the UK you live? (There may be grant support available)

What fuel shall I choose if I don’t have mains gas?

If you live off the gas grid, choosing a new boiler or heating system can be slightly more complex as you need to choose the fuel you’re going to use. Don’t forget fuel prices fluctuate constantly, so do your research before you choose a fuel.

Here a few of the most common options

Oil (usually kerosene)

Fuel prices vary throughout the year, right now oil is a fairly attractive option for off-grid customers when comparing running costs. It generally has a higher installation cost compared to LPG and you’ll need to consider if you have enough room for an oil storage tank.

Liquified Petroleum Gas (LPG)

Installing an LPG boiler will generally involve a lower outlay than an oil-fired boiler. There are also more options when considering fuel storage, but it will have higher running costs than an oil boiler.


If you’re (rightly) conscious about the environment, fossil fuels and your carbon footprint, have a little money to invest in a green heating system, then renewables can be an attractive option. The UK Government is banning gas boilers in New Builds from 2025, as an example of their commitment to climate change. There might well be similar restrictions in the pipeline for all residential properties in future…

Environmentally friendly heating options

Solar uses the suns energy to generate electricity, is constantly improving. With developments in domestic battery storage and greater efficiency of solar panels it can be an option.

Solar thermal combines electricity generation with heating your water though using jacketed tubes, it does have limited capacity for hot water generation and might need to be combined with other technologies.

Ground source heat pumps use the latent heat difference stored in the soil to create energy for heat and power.

Air source heat pumps do the same with the air around us. BOTH technologies are very well established and use the principle of a fridge working in reverse. They will both however increase your electricity costs substantially. BUT…you wont ever have any other fuel costs…

Renewables can especially attractive if you’re eligible to take advantage of the UK governments RHI Scheme.

Air Conditioning

Most people are pleasantly surprised when they find out the running costs of air conditioning, even when taking in to account the installation costs. It also adds the luxury of being able to cool your home in the summer, handy in these times of climate change.


Electric heating will generally have a lower installation cost, but a higher running cost than the other options. It does however offer a better level of flexibility, many options of appliances and is a desirable (or even necessary) option for clients with solar PV panels.

What brand of boiler should I pick?

The brand of boiler you install may be dictated by your budget. Obviously try to avoid going for the cheapest you can afford, because ultimately, you’ll get what you pay for. This can also apply to your installation quote… Its best to undertake research online, read reviews etc and possibly speak to family and friends about their experiences. Make sure you have a conversation with your installer about this, after all we spend all day installing and repairing boilers of all brands.

What controls should I use?

Fitting the correct size of boiler and radiators without the correct controls will undo all the good work you’ve done choosing the right boiler.

The controls you fit may be governed by how old or tech savvy you are but installing high spec, high quality controls will add to your systems efficiency and comfort levels. Again ask your installer about what the most efficient option is for your system.

Below is a brief description of the most common controls used in domestic heating systems.

Thermostatic Radiator Valve (TRV) This is a self-regulating valve fitted to radiators; it controls the temperature of a room by stopping the flow of hot water to the radiator when a set ambient temperature is reached.

Room Thermostat A room thermostat is a basic thermometer and a switch that is used to switch your boiler on or off automatically when a set ambient temperature is reached.

Heating Programmer A heating timer or Programmer sets when the central heating and/or hot water will be switched on (of off) automatically.

Programmable Room Thermostat A programmable room thermostat is basically a room thermostat and programmer combined. It will allow you to set your heating to come on at different temperatures at different times of the day.

Weather Compensation Weather compensation controls assist the heat source and help it to work at its optimum operation which will help lower running costs and boost comfort levels by sensing the outside weather temperature regulate your heating.

Optimum Start Optimum Start is a feature which will be built into your programmer. Normally, you set the program times when you want the heating to come on. With optimum start you set the program times for when you want to be warm, then the system decides when it needs to turn your heating on (or up) by sensing the outside and inside room temperatures.

That’s a brief overview of the options. Before deciding on any option, speak to a professional about it. Make sure they’re correctly trained, experienced and have appropriate credentials. Also, research to see reviews on their past installs.

Take advice, ask for a couple of quotes so you have a benchmark, but please use an appropriately qualified and experienced engineer. Someone who will freely offer advice based on years of hard-won knowledge.

Good luck (and please get in touch if you want help or advice)


Commercial Heating

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