Unvented cylinders come in two flavours - direct, which are heated directly by heating elements, powered by mains electricity; and indirect, which are heated via hot water coming from a gas-powered boiler. (There are other options, but these are the two that I"m looking at).
On the face of it, a direct cylinder should be better for the environment than an indirect one, because electricity comes from nice things like solar panels and wind turbines, but gas is a fossil fuel and evil. But:
- Green Gas uses (some) biogas, so isn't all evil
- If using electricity, I'd be heating the water between midnight and 6am, so presumably none of that electricity is going to come from solar panels
- Gas is allegedly "more efficient" but that seems to be more about £ per Kw than anything else.
- Electricity production isn't perfect, with greenhouse gases used in high voltage equipment, etc.
In general, it seems hard to find a direct comparison between the two options, so I'd welcome any thoughts/facts that people can add.
At the moment I'm still erring towards using electricity to heat the water, but I'd welcome thoughts on which is "better" environmentally. I know that electricity is going to push up my costs a bit, from something like £30 pcm to £45pcm but I'm prepared to pay for something that's better for the planet... if it is better!