what is the alternative to Gas boilers


What are the alternatives to gas/oil boilers?

If you are considering a more eco-friendly option for your gas heating we can help you make the decision.

At AHS, we believe Renewable Energy is the future, with rising energy costs and rising Co2 levels it has never made more sense, to see if renewable energy works for your home and your pocket. With technology constantly improving and changing, it’s a challenge to make an informed decision. In order to help make sense of the renewable energy marketplace we have explained the main choices available to the consumer:

There are a number of technologies, some of which provide heat, some electricity and some which provide both. We have broken the options down by the type of energy they produce.
  • Electricity only
  • Heat only
  • Heat and Electricity ( known as CHP, Combined Heat and Power )
Heat only

Air Source Heat Pump (ASHP)

These devices typically sit outside next to your home. Essentially ASHP uses the same technology as a fridge, only in reverse. Air Source Heat Pumps take the heat from the surrounding air via a fan, which gently heats a conducting liquid. This liquid is then compressed to raise the temperature to a useful level. This heat is then transferred to either a cylinder for storage or house heating and being deemed “low grade” heat is ideal for underfloor heating.

Another positive is installation is normally straight forward, the units themselves are often affordable (when compared to other renewable technologies), and uses technology which is tried and tested and very reliable.

The effectiveness of an Air Source Heat Pump is measured by its Coefficient of Performance (CoP) which provides the amount of Kw of electricity it takes to run the unit compared to the Kw of heat produced.

What are down sides to Air Source Heat Pumps?

Air temperature varies and the lower the ambient air temperature the less energy is available and typically, the lower the CoP, so whilst many ASHP’s can produce heat down to -15C, the efficiency drops off at low temperatures which is when you have the greatest need for heat. Also, the units themselves are not silent with different manufacturers ASHP’s producing varying noise output, and so it is worth checking the noise levels before deciding which ASHP.  Finally ASHP’s are best suited to under floor heating as this enables the unit to run at lower output temperatures (making them more effective in colder weather).

So when would an Air Source Heat Pump work for my home?

ASHP can deliver savings, especially when they are used in conjunction with underfloor heating ( wet systems ) and used in well insulated homes. In these circumstances an ASHP could provide heating all year round with significant savings during the spring, summer and autumn.

We recognise a key consideration for many is the initial cost, however, with the governments Renewable Heat Incentive (RHI) program house holders can receive 4 payments each year (quarterly) for 7 years which should offset the majority and potentially all of the initial outlay. There are conditions attached to receiving the RHI payments, many of which are explained in the attached FAQ’s document from Ofgem (2017) ;


If you would like to discuss ASHP and whether it could be right for you, please email (enquiries@ahs-heating.co.uk ) or call AHS who will be delighted to help.

Ground Source Heat Pump (GSHP)

This technology uses pipes that are buried in the ground to extract heat, and can be used for heating and hot water. A ground source heat pump circulates a mixture of water and anti-freeze around a loop of pipe which is passed through a heat exchanger into the heat pump. Since the ground stays at a fairly constant temperature under the surface the heat pump can be used throughout the year. The pipes used are typically either;
– ground mats which are a series of pipes buried not far below the surface (typically a metre or so). This requires a fairly large area (dependent on the heat requirement) and care when digging the garden! or
– Bore holes. These bore holes remove the ground mat concerns but the depth per bore hole can be between 60 metres to 150 metres and so the ground work costs are the most expensive part of the installation.


Currently available are either a biomass-only boiler, fueled by wood pellet, wood chip or logs, or a biomass pellet stove with a back burner (this includes boiler stoves). If you have your own wood supply or for those with good access to replenish the wood fuel this is a viable option but will naturally tend monitoring more than conventional heating and of course, burning wood releases the Co2 within the wood to the atmosphere so whilst renewable is not carbon free.

Electricity only

Solar PhotoVoltaic (PV) panels

The most common form of renewable electricity generation are Solar PhotoVoltaic (PV) panels. Typically installed on the roof these PV panels make electricity using the sun’s UV so work even on cloudy days. PV panels are a truly renewable energy source and usually have a long life span, they can be 25 years or more, so there is a great opportunity to get a good return on your initial installation investment. They also require minimal maintenance so the overheads are low. All sounds good so far, but of course the downside is they rely on sunlight. This means zero power is produced at night, and very low light levels can drop their efficiency by a large degree. Since many households often require more electricity in the evenings (lights on, watching TV, putting the washing on, etc ) the lack of available electricity means reliance on the national grid. One way to minimise this is to use battery storage, so that excess power created during the day is stored and used when its dark. We at Alexandra Heating Services believe battery technology will need to be an ever increasing part of a renewable energy solution.

Solar Photovotiac Systems Hampshire
Electricity only

Hydro Power

If you are fortunate enough to have a stream or river in your garden, and you have permission, the power of flowing water can drive a turbine which drives a generator to produce electricity. This is a true renewable and has the advantage of being constant, so can produce electricity day and night, and depending on the amount of water and its speed, can produce really useful power. Installation costs will vary but Hydro has the potential for a good return. The key is ensure you have all the permissions (probably planning permission and the environmental agency should be engaged).

There are many other technologies which produce electricity such as wave, tidal and wind turbine but we have limited our information to those technologies which have a reasonable opportunity to be available to domestic customers. Should you interested in installing any other technologies, call or email us and we would be delighted to discuss.

Heat only

Solar Power Water Heating.

Solar water heating systems contain a solar collector that faces the sun and either heats water directly or heats a “working fluid” that, in turn, is used to heat water. These are sometimes referred to as wet systems (for obvious reasons). This is a well known and well used technology and is a true renewable and efficient, however the same downsides as PV exist (no energy produced when its dark) but also has a higher maintenance cost.

Another form of Solar roof panel uses vacuum tubes instead of silicon based (semi conductor) panels. These are glass tubes with an absorber inside within a vacuum. These tubes achieve a higher energy absorption and therefore offer greater efficiency however they are typically more expensive.

Solar Thermal installation for your business
Heat & Electricity

CHP – Combined Heat & Power

CHP is a process in which both space/water heating and electricity are produced at the same time. Traditional CHP units have been operating at an industrial / community scale since the 1970s. Now since 2000, with rising energy prices, micro CHP designed for individual buildings has become economically viable. Effectively the micro CHP unit replaces the conventional gas central heating boiler providing heat and hot water as usual, but additionally providing some of the building’s electricity needs. The European Cogeneration Directive defines micro-CHP as all units with an electrical capacity of less than 50kW.

Fuel Cell

There are several types of fuel cell ( SOFC, PAFC and PEMFC ) but only one of these is currently available for the domestic market which uses PEMFC ( Proton Exchange Membrane Fuel Cell ) and is made by Viessmann and houses a Panasonic fuel cell. PEMFC is favoured as it requires much lower temperatures to operate, has a large install base in Japan ( we understand more than 200,000 units ) and provides an excellent ratio between heat and power ( nearly 1 : 1 ). Currently Fuel Cells need natural gas to provide the Hydrogen so if you do not have a gas supply this solution will not ( currently ) work in your home. For information and installation regarding the Viessmann Vitovalor please call or email Alexandra Heating Services.

CHP great heating in your home
Heat & Electricity

Internal Combustion Engine (ICE)

Another and more established form of CHP is the Internal Combustion Engine (ICE). ICs are more often used in small commercial premises and in large residential developments such as care homes. The internal combustion engine is a tried and tested technology, but engines in practice produce relatively high emissions when compared to other renewables, as well as noise.


Another form of combustion engine is the Stirling engine. These engines are external combustion engines (ECE), which allow continuous, controlled combustion resulting in very low pollutant emissions and high combustion efficiency. In comparison with ICE engines, Stirling engines have relatively long service intervals as well as lower running costs as well as being quieter – which makes them more suitable for domestic applications.

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