The ultimate guide to being efficient with heating and hot water

04 January 2017 | OVO Energy

Unless you’re running a full-spec recording studio and car maintenance workshop in your garage, the [majority of your monthly energy bill] probably goes towards providing heat and hot water in your home – particularly during the winter.

So if you’re trying to be more [energy-efficient] and cut back on costs, it makes sense to concentrate your efforts on streamlining your heating and hot water systems.

To start with, you need to know a bit about your heating and hot water systems (they may well be the same thing) and have a top-line understanding of how they work.

Typical combi boiler

You might have:

  • A central heating system made up of radiators and a boiler that also provides your hot water – this is the most usual kind of heating system in the UK[1].
  • Individual storage heaters, or standalone heaters, plus a boiler for your hot water.
  • A heating system that pumps warm air into rooms through vents in the walls, generated from a boiler that also provides your hot water.
  • [Underfloor heating] – but you’re unlikely to have this in every room, so it would probably work with one of the other systems listed above.

What is central heating?

With central heating, you have a single boiler heating up your water. This water is then pumped through pipes to radiators installed in different rooms around the house. The same boiler also provides hot water in the bathroom(s), kitchen and utility room.

The majority of central heating boilers run on mains gas, which usually works out [cheapest] and has the lowest carbon dioxide emissions of any fuel apart from wood. They can be either a [‘combi’ (combination) boiler] or a regular boiler:


A combi boiler provides hot water instantly, as soon as you turn on a tap. The water is heated as it passes through the boiler, so there’s no need for a cylinder, and you can have hot water for baths or washing up whenever you want.

A regular boiler works with a hot water cylinder. You programme it to heat the water in the cylinder at certain times of day, so there’s enough hot water at times when you want a bath or to do the washing up and so on. However, you can’t spontaneously decide to have a bath at random times of the day, as the water in the cylinder may have cooled down by then.

Has your boiler broken down? Don't panic: read our guide to common boiler problems, and how to fix them.

My home doesn’t get mains gas – what sort of boiler should I get?

If your home isn’t on the mains gas grid, your boiler could run on oil, [biomass] (basically wood), or liquid petroleum gas (LPG) stored in a tank outside your home.

Around a million homes in the UK use heating oil as an alternative to gas. Find out more in our complete guide. 

Electric boilers are also available. Although electricity is generally more expensive than gas, electric boilers can be programmed to make use of [off-peak electricity], and they can last longer than gas boilers. They can also be adapted to use renewable energy sources, making them very energy-efficient.

What is a condensing boiler?

Condensing boilers can be either [combi] or regular boilers. If you’ve had a new boiler since 2005, it’s almost certainly a condensing boiler. They’re more efficient than their predecessors as they have bigger heat exchangers that can recover more heat from the gas they’re burning.

Not sure whether yours is a condensing boiler? If you can answer ‘yes’ to these questions, then it is:

  • Does it have a plastic flue? (If it has a metal one it’s probably not a condensing boiler.)
  • Is there a plastic pipe coming out of the boiler, going through the wall and into a drain?
  • Was it installed after 2005 (if it’s a gas boiler) or 2007 (if it’s an oil boiler)?

Most people are very happy with their condensing boilers, but they do occasionally have a ‘plumage’ issue. Plumage is the flue gas that looks like white smoke and wafts around your garden (and your neighbours’, which is how problems sometimes arise). It’s more noticeable than the gases produced by older, less efficient boilers because it’s much cooler and concentrated in water vapour.

Having trouble with low pressure on your boiler? Save yourself the hassle and cost of calling out a professional and solve the problem yourself with our easy-to-follow guide.

How can I create a more energy-efficient heating system in my home?

  • Turn down the thermostat. According to the Energy Saving Trust, just 1 centigrade could save a typical home around £90 per year.
  • If you haven’t had a new boiler within the last 10 years, look into replacing it with a newer model. Boilers are improving and becoming more energy efficient all the time.
  • Radiators have also improved over the years, so look into replacing your current system with newer, more energy-efficient radiators. And if you haven't bled them recently, find out why that's a good idea, and how to do it, with our handy guide.
  • Use the timer controls to make sure your system isn’t providing heating when you’re out. Set it to switch off a while before you’re due to go out to work, or go to bed, so that your home is just starting to cool down as you leave/snuggle down.
  • Fit individual thermostats on every radiator, so you can control the heat levels in each room.
  • If you have a regular boiler, make sure it’s only set to provide as much hot water as you need, when you need it, and not wasting energy by heating up water that then just cools down overnight or during the day while you’re out.
  • Find out whether your controls or thermostat will work remotely, so you can switch on the heating exactly half an hour before you’re due to arrive home, rather than always switching on at the same time each day, whether you’re in or not.
  • Make sure your home is well insulated and draught proofed.
  • Change to a cheaper or lower-carbon fuel or technology – this is a great way to create totally energy-efficient heating systems, but it may be expensive and disruptive, so do plenty of research before you decide.
  • Add chemical inhibitors into your radiator system to make sure it keeps flowing freely.

We've also put together an ultimate guide to help you improve your boiler efficiency, and an explainer on how to use your heating efficiently during the winter. Plus learn how to stay warm over winter without using so much heating. And if you ever have a problem with your boiler, check out our guides on how to reset your boiler when it locks out, and how to decide when to repair or replace your boiler.

I have electric storage heaters – how can I use them more efficiently?

Electric storage heaters are one of the most expensive heating choices in the UK, and their CO2 emissions are worse than most other systems. They’re also not as controllable as other systems, so they tend to waste energy by heating rooms at times when it’s not needed.

However, there are a few ways you can improve your storage heaters’ performance:

  • Replace them altogether with a different system! (Expensive but effective.)
  • Upgrade to newer, more controllable models.
  • Fit extra thermostats and controls, if your heaters can work with them.
  • Make your home more energy efficient by installing draught proofing and insulation to reduce heat loss.

Is it more energy efficient to use individual heaters rather than switch on the central heating?

[Individual heat sources] that work separately from your central heating and water heating systems could be portable heaters, wood-burning stove, open fires, range cookers or gas fires. They’re not usually as energy efficient as a central heating system, but if you only need to heat one room for a while, it may make sense to use a single heater rather than switch on the whole system.

Portable heaters are also useful if your central heating system heats most of the house very effectively, but there’s one area that’s always chilly. There’s no point in turning up the whole heating system for a single room, so adding a portable fire or other heat source in the cooler space can be the most energy-saving way to make the room comfortable. It’s worth checking the insulation as well, though, to find out why it’s so chilly.

Find out more by reading our guide to energy-efficient heaters that can be used at home.

*Source and notes