Heat pumps – Air / Ground Source
Heat pumps are an effective replacement for a traditional boiler, they do not burn oil or gas so have a smaller carbon footprint. They work by extracting heat from the air, ground or water and use a compressor to increase its temperature and transfer the heat into the hot water and central heating systems. For hot water they are just as good as a gas boiler. For heating, they work most efficiently at a slightly lower temperature, so some homes may require radiators with higher outputs (not necessarily larger).
Their key advantage is in the efficiency as they typically produce 3 or 4 times the amount of heat energy than the energy required to power them, in percentage terms this is 300-400%. This compares favourably to gas/oil which can be 85% at best for a new modern boiler and a 20 year old boiler is likely to be as low as 60% efficient. Air Source Heat Pumps are fairly compact and quiet, so can be easily located in most gardens.
A cold weather test to see if you are Heat Pump ready
Many who are interested in the idea of installing an Air Source Heat Pump (ASHP) in their home are unsure if their property is suitable. Much has been written concerning the need to ensure that your property is adequately insulated and fitted with radiators of sufficient size before undertaking the work.
A test to give an idea whether your home is ASHP ready, without embarking on a potentially expensive survey from a specialist firm, can be made during cold weather. In fact, it’s best carried out for a few days when the weather is at its coldest. This test is not perfect, but can give you an idea of whether you can heat your home with the lower output temperature of water, typically 50°C, in an ASHP system.
To perform the test, you can easily turn your gas boiler output temperature from its normal operating temperature of 60-70°C down to 50°C. You then need to change the programmer settings so that the boiler is on permanently, all radiators are fully open, and the system is controlled by a room thermostat set to your usual preferred temperature. In this way your boiler is mimicking an ASHP which normally runs continuously. If the house remains at your set temperature regardless of the cold weather then your house can be said to be heat pump ready. If only one or two rooms fail to reach the set temperature it may be that installing larger radiators in those rooms could remedy that problem. If, however, the whole house gets too cold then more insulation and larger radiators are probably required.
Further information:
Which ‘Warming up to change: Homeowners’ uptake and attitudes towards home energy technology’
Electricity
Electricity is the cleanest form of energy to use in your home, particularly where the supplier generates power from renewable sources such as wind, hydro and solar. You will have heard that the market is competitive for electricity so it is worth getting the right tariff that suits your needs which will depend on your lifestyle and how much time the home is occupied. The best deals tend to require a smart meter so you can use cheap energy at off peak times and they encourage you to use less electricity when demand on the national grid is highest.
Solar panels on a house can power electrical appliances and charge an electric car, so can save money and reduce the burning of fossil fuels. Solar panels can be retro fitted to most properties, though planning regulations must be observed, depending on the location and category of the property.
Batteries / Energy storage
Changes in how we power our homes has evolved considerably in recent years. Houses with solar panels are likely to generate excess electricity on long sunny days so having energy storage is a sensible way to manage production using either batteries or thermal storage (heating water in a cylinder or heat storage batteries). Electric cars can provide additional battery storage for a house, being charged from solar or charging with cheap power via smart tariffs from energy providers.
Additionally batteries can be used to reduce energy cost by charging them at off peak times and using the stored electricity in the home at peak times. An increasing number of electric cars offer this functionality, to the extent that a car battery can power a home for upto two days. This concept of bi-directional flow was first used for Vehicle to Grid (V2G) which enables the energy company to balance supply and demand so may buy electricity from your battery at peak times and top up the battery during off-peak hours.
Gas
In cities like Edinburgh, the network of mains gas makes it the most common way to heat properties and produce hot water. They do burn fossil fuels so are not good for the environment and the UK government intends to ban the selling/installing of new gas boilers in the UK from 2035.
To optimise the efficiency of your gas boiler, you might want to consider:
- Regular maintenance of the boiler by an approved plumber
- Use the boiler regularly
- Insulate the hot water cylinder and pipes
- Ensure the system has sufficient pressure
- Regularly bleed the radiators
- Use a smart thermostat
If your gas boiler is over 15 years old, it will be less efficient and you might want to consider replacement with a heat pump or at least a more efficient system.
Oil
Oil is less common in Edinburgh but some homes do use it. Burning oil produces much more carbon than burning gas, so it is important to take steps to optimise its efficiency, as mentioned for gas. If the system is over 15 years old the best action would be to replace it, ideally with a heat pump.
The table below compares the amount of CO2 emitted per unit of energy/heat output in pounds of CO2 emitted per million British thermal units (Btu) of energy for various fuels.
| Anthracite coal | 228.6 |
| Heating oil | 161.3 |
| Propane gas | 139.0 |
| Natural gas | 117.0 |
| Heat pump (with renewable electricity) | 0 |
Ventilation / Heat Recovery Fans
Most bathrooms have an extractor fan that sends warm air out of your home. Ventilation with heat recovery works by extracting heat from expelled air that would normally just go into the atmosphere. It then transfers this heat to incoming fresh air as it comes into the home with a heat exchanger. The system then distributes this warmed air throughout your home. They generally save more money than the cost of running them.
Waste Water Heat Recovery (WWHR)
This is an effective way of recycling the heat from waste water, by using it to raise the temperature of water going into your system. In an average home about 34% of energy used is in making hot water and half of that is used for showers. WWHR can reduce the energy used by a shower by 55%. Showers typically run with water at 40c, when the hot water reaches the drain it has only lost a few degrees (around 34-37c). So installing a heat recovery system can preheat mains water from around 10c to around 25c, so reduces energy requirements, lowering CO2 emissions and reduces energy bills.