Domestic and small commercial combined heat and power (CHP) boilers are starting to reach the market from multiple companies. Is this the next step for consumers and businesses after solar PV?
Some historical context

Solar PV was available for decades in small volumes and at high prices before it reached a tipping point where volumes quickly rose and prices quickly fell. Domestic scale CHP boilers may well be on the same path.

Originally CHP (combined heat and power, i.e. generating electricity at the same time and with the same fuel as the generation of heat) was only for large industrial sites. Then slightly smaller scale CHP boilers came in for commercial buildings which were still relatively large for their output, were very noisy and required lots of servicing. Most recently micro CHP boilers have become available which are quieter, more efficient and need less servicing. In case you were wondering, in this context “micro” means domestic scale, not microscopically small!

In the early 2000s domestic scale micro CHP boilers were first announced and even trialled by the Carbon Trust. The trial confirmed the potential of micro CHP boilers, particularly in small commercial buildings, and also the performance improvements required to make them commercially viable. The companies involved set to work on improving those real world results.

Government support

Some years later, in 2010, domestic or ‘micro’ CHP boilers were included in the UK Government’s feed in tariff. This was the first real incentive and as a result some hundreds of CHP boilers were installed in the first few months and it looked like the market had finally started, albeit with just one product from one company. This dependence on one manufacturer meant that when sales suddenly collapsed no other substitute products were available and even an increase in the feed in tariff couldn’t stimulate the market.

Most recently the mood has changed again to a much more positive one. The huge success of solar PV has convinced investors that low carbon and renewable technologies are here to stay and some really innovative business models have been developed. At the same time more and more companies are lining up to bring new micro CHP boilers to market. This time around the feed in tariff is already higher, energy prices are higher, savings are therefore higher and the market has a better idea as to what to expect.

The next generation of boilers

But, I hear you say, why would anyone want a CHP boiler anyway, if modern boilers are already so efficient? The answer is very simple – it’s all about the electricity.

A gas boiler uses gas to create heat and uses a small amount of electricity for its control systems. So, if the lights go out, the boiler goes off too, even though there is no break in the gas supply.

A CHP boiler uses gas to create heat with electricity as a by-product. It’s also 90% efficient, just like a modern gas boiler. The proportion of heat to electricity produced depends on the technology and individual product, with Stirling engines (such as the Inspirit Charger) producing 5 units of heat to 1 of electricity. This mirrors the demand profile of the average UK home, which consumes 15,000 units of heat and 3,300 units of electricity every year (source: Ofgem). In essence the Inspirit Charger could generate all the heat and all the power used by the average UK home, with almost no electricity taken from the grid.

In reality, of course, life isn’t that simple. Electricity storage is only just starting with products like Tesla’s Powerwall and heat and power isn’t always needed in that nice, easy, 5 to 1 ratio. Nevertheless, gas is typically around one quarter of the price of electricity and the electricity generated by a CHP boiler is produced at only slightly more than the cost of gas, say under one third of the cost of electricity. Wouldn’t you like to lower your electricity bill by more than two thirds?!

National impact

Once sales of micro CHP boilers start to scale up (and remember that around 1.6 million boilers are sold in the UK every year, more than in any other European country) then these products will have a national impact. 1 million Inspirit Chargers could generate in one hour about as much electricity as the proposed nuclear power station at Hinkley Point C and approximately 6% of the UK’s peak winter demand. Unlike solar PV this electricity is generated when there is a demand for heat, which is typically during the cold winter months when the sun shines least and when the UK experiences most demand for electricity.

Hinkley Point C is estimated by EDF to be operational in 2023 but that’s assuming no more delays, whilst our Inspirit Charger micro CHP boiler will be at market long before then. As we’ve seen with solar PV, the market often reacts quicker than energy companies can keep up.

Source: Carbon Trust

Combined heat and power boilers are inherently efficient as they use less fuel by doing two things at the same time. Even when burning natural gas they reduce carbon emissions. In fact the average home will save more carbon with an Inspirit Charger than with solar panels and the larger the home, the more carbon it will save. The same goes for saving money on utility bills, with the Inspirit Charger coming in ahead of the solar PV equipped home, with larger and “hard to heat” homes saving most. Even better, for someone who already has solar PV installed, a micro CHP boiler reduces carbon emissions and energy bills still further with the micro CHP boiler running during times and seasons when the sun doesn’t shine, or only dimly.

Typical Profile of Residential Use Building
  • 4kW PV electricity generation (kWh)
  • Building electrical power consumption (kWh)
  • 2kW heat led Inspirit Charger 2.0 electricity generation (kWh)

Graph is an illustrative comparison of generation and consumption only. Actual figures may vary according to building size and use

For anyone doing a ‘self build’, i.e. planning to build their own home, and for professional housebuilders and developers, the carbon savings from micro CHP boilers can help them achieve compliance with Part L of the Building Regulations through SAP (or SBEM for commercial buildings). This can sometimes make the difference between a project going ahead or not, particularly where solar PV panels are not suitable or not sufficient.

Homes and businesses

One of the great advantages of a micro CHP boiler is control. The micro CHP boiler will come on in response to heat demand but you can adjust your demand for heat fairly easily using a thermal store. The heat is stored until you need it and the micro CHP boiler can be made to run when you most want the electricity. Often the two happen at the same time but sometimes not. Why not charge the hot water tank up in the evening when you can use most of the electricity generated instead of during the early hours of the morning when everyone is asleep and electricity demand is at its lowest? It’s great being in control!

Importantly, it’s not only about individual homeowners. Just like solar PV, there is also a large market in commercial buildings such as hotels, gyms, sports centres, restaurants, pubs, nursing homes, care homes, schools, student accommodation and affordable housing. Commercial properties represent about one fifth of the total boiler market. The owners of these properties tend to have access to money to invest now for long-term benefit in a way in which most homeowners do not. These are likely to be the early adopters whose lead gives confidence to this emerging market.