Patio heaters might impress Dragons, but green credentials are hot air

Eddie Middleton told the Dragons' Den his electric heaters produce less CO2 than the gas version. But can it be true?

Fred Pearce
guardian.co.uk, Thursday 30 July 2009 11.00 BST
Anybody watching the BBC's Dragons' Den a couple of weeks ago may have sat up straight when Eddie Middleton walked in and pitched for money to invest in making his eco-friendly patio heating.
Eddie claims that his heaters, which have names such as Zeus and Neptune, produce 50% less carbon dioxide than regular patio heaters because they run on electricity rather than burning LPG gas.
This matters. Demand for his products is good. His company website says that "due to very high demand", Neptune is out of stock.
Also, according to the Energy Saving Trust, a non-profit adviser on low-energy living, there is a "patio pandemic" going on, with more than 1m of these backyard Humvees polluting the skies above British suburbia during summer evenings.
Eddie told me he is not quite saying it is climate friendly to heat the air over your back garden. More that, if you are going to heat the atmosphere, then you should buy one of his heaters to do it.
But is it true? According to the Carbon Trust, another government-backed advisory body, grid electricity produces more than twice as much carbon dioxide to deliver a unit of energy than LPG.
So how can Eddie make his electric heaters produce less CO2 than their gas rivals? His number crunching is carried out by Andy Lowe at Carbon Clear, a private "carbon management" company. Eddie sent me Andy's calculations.
They start with an estimate provided by the Energy Saving Trust that a typical British gas patio heater produces 50kg of carbon dioxide during a typical year's use.
Andy reckons that, given how much gas an average patio heater consumes, this means it burns for 21 hours in a typical summer. He then says that if you run Eddie's Neptune heater for 21 hours, it produces just 26kg of CO2. Only half as much.
Fair enough. I have no problem with any of those numbers. But there is an obvious question. Does the Neptune produce as much heat as a regular gas heater? If it doesn't, then surely the comparison is invalid.
Here comes a bit of maths, so bear with me. If the average gas-powered heater emits 50 kilograms of CO2 during 21 hours of operation, then it must emit 2.38 kilograms for every hour it is switched on. Now, according to the Carbon Trust's Greenhouse Gas Conversion tables, a kilowatt hour of energy from burning LPG produces 0.214 kilograms of CO2. So to emit 2.38 kilograms of CO2 in an hour, the "average" heater in Andy's calculation must have a heat output of 11.1 kilowatts.
But Eddie's Neptune – which is advertised, I notice, as "the baby of the range" – is a 2.3 kilowatt heater. It has not much more than a fifth of the heat-generating power of the "average" gas-fired patio heater. It is no wonder it kicks out less CO2, because it kicks out a very great deal less heat as well.
When I put this to Andy, he insisted that the Neptune heater is "a direct replacement" for bigger gas heaters. "Advances in technology have made it possible to deliver a comparable heater which uses only a fraction of the energy."
How's that? He said that "70% of the heat generated from a gas patio heater is lost". It heats the air and not people sitting close by, he said, whereas his infra-red electric heater heated only the people.
Well, he has a point here. Physicists among you will know that radiant heat from an electric heater is more efficient at warming objects, like people. But I am still hoping for the documentation to back up that claim that there is a 70% difference in heat delivery.
Even assuming he is correct though, Eddie's Neptune heater is still producing substantially less heat than its rival. So his claim to produce 50% fewer emissions is not justified.
I don't think Eddie is trying to pull a fast one. He is an enthusiast. But if you make such claims about a product selling out after TV exposure, you need to be able to back them up. He may be a straight guy, but his claim is greenwash.
Actually, though, isn't this all nuts? Isn't the truth that the world does not need patio heaters? Back in the real world, they are a disgraceful waste of energy, however they are powered. And calling them environmentally friendly is an insult. What's wrong with a pullover?
• Do you know of any green claims that deserve closer examination? Email your examples to greenwash@guardian.co.uk or add your comments below