How to Choose an Efficient Gas Boiler

December 15, 2020 7:16 am

Choosing a gas boiler can be a daunting task when faced with so many makes, models, kW ratings available, and optional extras to choose from. To help we’ve some information for you to consider, depending on your needs and budget.

First questions why do you want to change your boiler? Is it broken, just old and tired, needs upgrading to a more efficient one, better accessibility with an app linking to your smartphone, something more eco friendly, more compact, or a higher efficiency rating, etc? The list goes on.

A new boiler installation is a big investment, it’s important you choose one that exactly fits your needs. The purpose of new modern boilers is to provide reliable heating and hot water on demand, and be more Eco friendly, no surprises there?

Modern-day boilers can last for 10-15 years if serviced and maintained regularly. A boiler may show signs that it’s near the end of service life when breakdowns occur more often and the cost of a repair nearly exceeds the cost of replacing the boiler? If your boiler is insured the insurance company may cease to insure it, or increase the insurance premium, condemn it, if it’s too old and beyond economical repair (BER).

We at Marvel Property Solutions understand how confusing choosing a boiler can, so the following information we hope will help to identify the best boiler to satisfy your needs. Elements like size, energy-efficiency, fuel compatibility, and boiler position are a few considerations. Here we go.

Boiler Types

There are three main types of boilers available; Combination, System and Conventional.

Combi Boiler

This provides instant hot water when a tap (connected to the main water supply) is turned on, no waiting for the water to run hot before you get under the shower, it heats within seconds, unlike a conventional system. A combi could also save on your energy bills and water bills (if your water is metered?). The other benefit is a space-saving one. You can dispense with the hot water cylinder in the airing cupboard and the water feed tank in the loft.


There are a few: If more than one outlet requires hot water at the same time there can be a reduction in water pressure. Also, if the boiler breaks down you don’t have the benefit of an immersion heater (water heater) as backup!

Conventional Boiler

Also referred to as a ‘regular’ or ‘heat-only’ boiler. Quite a large number of households have moved away from this type of boiler in favor of the ‘combi’. It consists of a hot water cylinder and a tank making water available on demand. However, it does take a short while for the hot water to travel the pipes to the outlet. They have a central heating header tank and hot water feed tank both concealed(usually in the loft.


A conventional boiler is capable of producing hot water a home requires. Of course, this will depend on the boiler size you choose (kW rating) but is more than able to heat up copious amounts of water to manage your heating and hot water requirements. Unlike a combi boiler, there are no problems with water flow reducing when using multiple outlets.


The tanks take up room! If you’re pushed for loft space it’s a bit inconvenient. So, you may want a rethink if space is limited? The hot water cylinder will also require insulation, although many cylinders today come pre-insulated with a hardened foam jacket.
Water isn’t heated on-demand, like a combi boiler, it takes an amount of time to heat.

If there is a water supply problem at least you have a water supply in ‘storage’ as it were, to tide you over until the supply is reconnected. Just make sure your hot water demands do not exceed what’s stored in the feed tank or hot water cylinder, otherwise, you will have to wait for it to refill and heat up!

System Boiler

Coldwater enters the boiler straight from the mains water supply. The water is heated by means of a heat exchanger. The heated water is then pumped into a hot water cylinder for storage until required.


Installation tends to be much easier than other boilers as it has many individual features already designed it. This makes it quite compact, but the white box slightly bigger. Other benefits include: –

  • Strong water pressure
  • Good for high water demands
  • Can dispense with the cold water feed tank
  • Quick and economical
  • Cheaper running costs


  • Usually, take up more space
  • Longer waiting time if the cylinder empties to heat water
  • The cylinder needs insulation (if not supplied wrapped in hardened foam)
  • Pre programming the boiler each time if the water is needed at a certain time

So, there are a few things to consider when investing in a new boiler.

Buyer’s Guide

If you have concerns about consuming fossil fuels (natural gas being one of them) and the impact they have on the environment, then it’s going to be an influencer when selecting your new boiler. You may live in a rural location where oil or solar energy is the only option? There are many solar energy schemes available that need to be researched to see if the benefits outweigh that of a conventional natural gas or oil heating system? If they do, it could well be the system you plumb for?

Natural gas is the most common source of energy available for domestic central heating systems and typically available in the majority of areas. Rural areas that are ‘off-grid’ find it more expensive to heat their homes, which causes a problem for the rural poor. However, if you really want to be eco-friendly and prefer a green and clean environment then you can switch to biomass, but storage space might be an issue.

The fuel used is wood logs, chips, or pellets all of which are renewable, unlike gas, coal, or oil that took millions of years to form.

Another consideration is an electric boiler?. Electric boilers typically have similar functions to a natural gas boiler. An element heats the water as opposed to a flame. Electric boilers are easier to fit and compact in size that’s why many newly build apartment blocks prefer to install electric boilers. There are no combustible fuels within the boiler so no risk of gas leaks or explosions. An important safety feature. (Serviceteam electrical and installation department cover electric boilers).

Boiler Size

The kW rating of a boiler depends on the size of your property (small, medium, large). Once the calculations are complete the size of the boiler becomes clear. Providing your heating and hot water requirements are adequately met you can make the decision. However, the new boiler might not fit into the space occupied by the old boiler, which may mean a different location for the new one? A point to bear in mind.

A boiler of 24 to 27 kW is just right for a house with three bedrooms a single bath and a shower. For a 3 – 4 bedroom house (medium/large) with a couple of bathrooms, the 28 to 34 kW output is better. Contact service team for any advice on boiler size before making a decision, extra advice might throw up a few factors not considered? Nobody wants a substantial outlay on the wrong boiler!

You will have considered, the number of bathrooms, number of radiators, the number of inhabitants, and estimated water usage. Lastly, be mindful of the property’s insulation, as it can affect the load on your boiler and ultimately the boiler size.
When you have made your choice be open to the fact that you might have to make some adjustments to the level of insulation within your property.

Boiler Position

With the modern design of boilers, you can choose between a wall-mounted or free-standing boiler. Repositioning a boiler may incur additional modifications i.e. extended pipe run/s etc.

Water pressure

Is the water pressure supply to your property sufficient for the boiler of your choice? Serviceteam will do a thorough check on water pressure, siting of the boiler, kW rating, and much more during a survey. This ensures the boiler can cope with the current circumstances and family needs.


Always check the conditions outlined in the Manufacturer’s warranty to make sure you do not fall foul of the small print that can invalidate a boilers warranty! When a new boiler is installed the manufacturers will insist that the boiler is serviced annually to comply with the guarantee/warranty conditions. Guarantees offered by most manufacturers can range from 5 – 10 years (subject to conditions).


Efficiency saves expense costs while keeping the emission of harmful gases to a minimum. Low-temperature gas boilers and condensing boilers containing these features might seem pricey but tend to be more economical to run.
Boiler ratings use a SEDBUK rating (Seasonal Efficiency of a Domestic Boiler UK). Every new boiler has an ErP sticker ranking its efficiency. The rating is from ‘A’ – ‘G’ it’s always advisable you check this when making your selection. Many modern gas boilers will be ‘A’ rated (or close to it) See the guide below.

Top-rated boilers can reach 90% inefficiency, as vast improvement and better than ever.

Heating Controls

Smart technology has already reached the humble gas boiler. A thermostat switches off the heating when the ‘set’ temperature is reached. The latest thermostats are smarter and more intelligent, when connected to your boiler – via your existing thermostat wired connection – and your home Wi-Fi network.

Moreover, the temperature in each room in the house can be set differently. This helps in rooms that are seldom used or not used at all saving on heating costs.

Whoa! just a minute, TRV’s (Thermostatic Radiator Valves) fitted to radiators also control a room’s temperature independently and can shut off a single radiator if required, can’t they?

Okay, we admit you have to manually adjust each individual radiator valve in a room every time the temperature needs adjusting, which might be inconvenient for some? With smart technology, you can do it all via the app on your smartphone, and you don’t have to physically ‘lay hands-on’ anything (other than your smartphone keyboard).

You can also be in a different location, at work, on holiday many miles from home, and still, control your heating 24/7 (providing you have a decent signal). Which is a fair point!
So, is remote smart technology for you? Something else for you to consider?

Decision time?

We’ve covered a few key influencers to consider when shopping for a ‘new boiler’ and hope you will bear them in mind prior to your purchase?
You know a new boiler, plus installation costs are never going to be a cheap investment (no doubt you’ve already trawled boiler prices), but with the right selection, it can prove to be beneficial over the long term saving energy and running costs, not to mention your contribution to the environment.
If your still unsure, remember you are never alone, call Marvel Property Solutions, we will offer the best possible solution once we’ve investigated your heating needs, evaluated your situation, and presented the pros and cons. We will formulate the best option for your family’s needs and then plan the installation.
Call Marvel Property Solutions now on 020 3925 6453

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