It can be hard to tell which form of heating will work best for you. There is a government grant, called the Boiler Upgrade Scheme, or BUS scheme for short. It pays £5,000 towards installing a biomass boiler, or air source heat pump, or £6,000 towards a ground source heat pump, but what are the pros and cons, and is it worth changing over to renewable heat sources, or should you stick with your old fossil fuel heat sources? Of course it depends upon why you’re considering change and what your views are on the environment, and what type of property you’re trying to heat.
As with most things, the answer depends upon your budget and your circumstances. If you were starting from scratch I would say you couldn’t do much better than building a passive house with an air to air source heat pump, solar panels and battery storage. This will give you the lowest build cost and long term stability in terms of cost. The heat pump can also be reversed during hot weather to provide cooling.
Example scenarios:
1970s house, mains gas boiler, open fire, just want the quickest, cheapest way of getting the heating bill down.
You can’t get BUS grant for biomass because of the gas main connection (you’re not eligible for biomass if the property is or has ever been connected to the gas grid). You can get BUS grant on an air source heat pump (ASHP). If your heating needs are low, at around 4kWh and below, it may be possible to get an ASHP installed with the BUS grant fully covering the cost. Assuming the house needs 14kW down to 4kW (you can work this out by taking the annual kWh usage and dividing by 2,000). Your cheapest option is probably a wood burning stove. Stoke it up and leave all the internal doors open, prices start around £1,500 installed with a flue liner.
1850’s solid stone walled thatched cottage with outbuildings, oil heating
Difficult one. Depending upon your post code and proximity to the gas grid, you would probably be eligible for the BUS grant on biomass. To change to biomass is going to cost you a minimum of £5,000. If you go for a log boiler, and you have cheap or free access to seasoned wood the future running costs will be very low, but it will need stoking at least once a day during the colder months and it will become a chore if you’re the only person doing it. An entry level pellet boiler will come in around the same budget, but fuel cost is about the same as oil at the moment. ASHPs probably aren’t going to work well or be cheap to run, as the property is likely to be draughty and poorly insulated.
Best advice: Insulation, insulation, insulation
The best investment you’ll ever make to help with future heating bills is insulation and draught proofing. You may think there is nothing you can do with the type of construction your property was made with, but there are many types of insulation you can retrofit:
Cavity wall
- Glass fibre fill
- Polyurethane foam fill
- Polystyrene fill
Solid wall
- Internal insulation, such as foam backed plasterboard on dabs, or an internal timber framed wall, multilayer type blanket on battens that are plasterboarded over
- External insulation, such as a multilayer type blanket on battens that is boarded over with a wood finish, composite board, or ply, steel scrim and render
- Polystyrene block insulation with resin render finish (necessitates eaves extension in most cases)
Roof insulation
- Layer up with fibreglass blanket
- Multilayer foil blanket
- Polyurethane foam boards
Draught proofing
- The usual door and window seals, such as foam sticky-backed tape
- Secondary glazing
- Chimney bag, to stop chimney draw when the fireplace isn’t being used (don’t forget to remove when lighting a fire)
- Plug random gaps with caulk
- Install underfloor semi permeable membranes (these can go under carpet if you don’t feel like lifting boards)
Heat recovery systems
- It can be difficult to retrofit a heat recovery system, but the idea is that it expels warm wet air from places such as the bathroom or kitchen through a heat exchanger that replenishes fresh air in the property and uses the heat from the expelled air to warm the fresh air before it is discharged into the property
Watch points
With insulation, in each case you should bear in mind vapour barriers to avoid interstitial condensation, which can cause mysterious damp patches and timber rot. With draught proofing, please bear in mind that gas and solid fuel appliances need air for combustion and cooling, so check with a trade professional that any air bricks are of a correct size once you have draught proofed.
How much heat do you need?
Assuming you’ve got insulation covered, you can look at the cost of heating with various technologies. We talk in terms of kilowatts per hour, so if you’re looking to work out how much heat your home needs, the first step is to work out how much heat your home loses per hour. There are various free radiator and boiler sizing tools on the internet that will help you work out the heat loss for your home and the size of the boiler you will need in kilowatts per hour output, or kWh for short.
Currently, there’s an energy price cap, which was introduced by the government on the 1st October 2022 and will run until the 31st of March 2023 (it’s been extended). It limits the price domestic customers pay for gas at 10.3 pence per kWh, and 34 pence per kWh for electricity. Sadly it doesn’t apply to LPG for gas, and kerosene (also known as heating oil) is also excluded. For working out your cost per kWh for electricity is as simple as looking at the data badge of whatever you’re planning to use and it’ll tell you what its rating is. Something like an old tungsten filament light bulb might say 100W on it, so that’s a tenth of a kWh. Under the new price cap it’ll cost you a tenth of 10.3p for every hour that you use it, or a penny and a bit per hour. It’s not quite that simple, because energy companies have cottoned on that they can put up your daily charge for having electricity, but it’s generally no more than 50p per day on top of your usage, so about 2p per hour whether you’re using it or not. You might as well blow another penny and have the light on then.
With gas, biomass and oil boilers it’s slightly more difficult to work out, unless you’ve got a heat meter installed. Reason being the boilers aren’t working at full load all the time. All you can do is measure the amount of fuel it’s using and from that you can work out the number of kilowatts of heat energy being produced. If you’ve bought the property recently, or it’s rented, there should be an EPC (energy performance certificate) for the property, unless it’s listed. This will tell you roughly how many kWh of heat the property will use in a year and will often make recommendations on how the bills can be reduced and how much difference each measure will make.
The low down at the moment is:
Gas 10.3p/kWh
Electricity 34p/kWh
Heating oil 10p/kWh
Wood pellets bagged 13p/kW
Wood pellets bulk 10p/kW
Wood chips 3p/kW
Wood logs 5p/kW
These are the best prices I could find, and the chip price is for wood bought in the round, stored and chipped when seasoned. This will change throughout the summer months as demand drops.