The media tends to forget that some people are not on the gas network. Most who are off gas are acutely aware that this means high energy bills. But what are their options? Essentially the choices boils down to 4 options, each with some subsets. I’ll give a brief overview of each of these with some good and bad points.

Direct electric heating

The two options here are on-peak electric heating and off-peak storage heaters.

On-peak electric heating should be avoided in virtually all cases if possible – this includes panel radiators, electric underfloor, fan heaters and heated windows.  All are the  most expensive and most CO2 intensive way of heating your house. Do beware that less than honest salespeople will promote their ‘efficiency’. (please report them to the Advertising Standard Authority if you come across them – we can help you with this).  Whilst true that electric resistance heating is 100% efficient it’s just efficient at turning something very expensive into heat. They work out around 16p a kWh of heat delivered.

Electric storage heaters are slightly better from a cost point of view but a little worse in CO_2; they can lead to overheating as you have to guess tomorrow’s heating demands. Modern storage heaters have better controls and also can incorporate fans to allow them to heat up a room quickly when you want it.  You will need an off-peak tariff and this sometimes comes with a higher on-peak tariff. An off-peak storage heater works out somewhere between 5p and 11p per kWh as there are a large range of tariffs available.

Oil and LPG

Both of these require a tanker turning up every now and then and filling a tank. The difference between them is with oil the tank is owned by you and so you can shop around for the best oil price; with LPG the tank tends to be owned by someone else and so you get locked into a multi year contract. Other than having to have space for the tank and access to fill it, the system is similar to a gas central heating system in that it will have a boiler and radiators. Oil and LPG tend to be similar prices and about a 30-50% more than the price of mains gas. A new one of these boilers will be around 90% efficient so heating will be about 7p per kWh for oil and 8p for LPG.

Heat Pumps

The important thing to get your head around with heat pumps is that the energy they use is not for generating heat, but for moving low grade heat in the ground or the air into high grade heat in your radiators. For this reason they can have notional efficiencies of over 100% when you compare the energy you put in (electricity) to that which you get out (heat). There are two main options. Ground source heat pumps either require trenches to be dug and pipes laid over reasonably large area, or a borehole drilled – there are obviously land constraints involved.

Air source heat pumps are essentially air conditioning units running in reverse – i.e. not the most attractive and have some noise implications.

The closer the source temperature (air or ground) is to the radiator temperature the more efficient the heat pump. This means that air source tend to be both less efficient as the ground stays a steady 15 degrees a few feet down, and also air source efficiencies fluctuate and are at their lowest when it is coldest. Designing a system which requires low radiator temperatures, either oversized radiators, fan assisted radiators or underfloor heating helps efficiencies as it keep the temperature difference down from the demand end.  These sorts of radiators rely on a highly insulated and airtight houses or else the internal temperature never gets up to a desired level.

If also used for hot water then the efficiency is much reduced, as the temperature of the hot water has to be much higher.

A plus is that, if they are being installed into an off-gas property, heat pumps should be eligible for the Renewable Heat Incentive (RHI), if and when it actually launches.  The proportion of the energy that is from electricity will be netted off to give the amount that is eligible for the tariff, e.g. if a heat pump is deemed to be 250% efficient, then 150% of the heat is eligible.

Heat pumps efficiencies will probably be somewhere between 200 and 300 for air source and 300 and 400 for ground source.  This means air source works out around 5-8p and ground source around 4-5p per kWh.

Biomass

Again, this can be split into subsets. There is of course, the open fire/stove option which in most cases are only secondary or supplemental heating and will not be eligible for the RHI. A closed stove will be much more fuel efficient than an open fire.

For central heating, there are three main fuel sources – logs and coppice, wood chip and pellets. As a general rule, a biomass boiler is not a realistic option for a small property with little land.

Logs and coppice are the cheapest as they have the least processing. The downsides are that they have to be manually stored and loaded. On the plus side they can be a lot more forgiving on what you put in them. This also means that they are generally suited to batch burns with associated large thermal stores – a really big cylinder. The central heating then runs from the thermal store through a heat exchanger.

Woodchip can be a good option if you have storage space as they can be fed with an auger, whilst they are still a relatively cheap feedstock.

Pellet boilers are the most compact in terms of overall storage and can be fed from a hopper and can be a little more efficient – 90 rather than 85 for logs. As there is much more processing involved the pellets are more expensive and potentially harder to come by and potentially from wood from much further afield.

Both wood chip and pellet can be more ‘just in time’ heating and so some can get away with not have a thermal store.

Log, chip and pellet central heating boilers should be eligible for the most generous RHI tariffs but again we’d advise against banking on it happening.

This means that logs would be around 5-6p per kWh, pellet 7-8p and chip somewhere in between.