ity and building-heating.

I’m going to build up a diagram in three steps. The diagram shows
how much electrical energy or heat energy can be delivered from chemical
energy. The horizontal axis shows the electrical efficiency and the vertical
axis shows the heat efficiency.

### The standard solution with no CHP

In the first step, we show simple power stations and heating systems that
deliver pure electricity or pure heat.

Condensing boilers (the top-left dot, A) are 90% efficient because 10%
of the heat goes up the chimney. Britain’s gas power stations (the bottom-
right dot, B) are currently 49% efficient at turning the chemical energy of
gas into electricity. If you want any mix of electricity and heat from natural
gas, you can obtain it by burning appropriate quantities of gas in the
electricity power station and in the boiler. Thus the new standard solution
can deliver any electrical efficiency and heat efficiency on the line A–B by
making the electricity and heat using two separate pieces of hardware.

To give historical perspective, the diagram also shows the old standard
heating solution (an ordinary non-condensing boiler, with an efficiency of
79%) and the standard way of making electricity a few decades ago (a coal
power station with an electrical efficiency of 37% or so).

### Combined heat and power

Next we add combined heat and power systems to the diagram. These
simultaneously deliver, from chemical energy, both electricity and heat.