So, with an 18 yr payback on the battery storage and anywhere between 8.5 and 25 years for the PV installation, what am I missing that can turn this from a frivolous indulgence to a frivolous indulgence with a sporting payback.
What if we use the PV generated electricity for the hot water requirements instead of the current oil heating – having checked that we still have a working immersion heater.
The Energy Saving Trust, reckons that the average household of 2.4 humans and a dog would use 349 l per day, of which 25% goes on showers – say 87 l. If we throw in an additional, arbitrary 13 l for washing up, this give a nice round 100 l per day.
Assuming the water is heated from 10 to 60 degC and reaching back into my understanding of physics, gives a figure of around 5.75kWh / day.
An 88% efficient oil boiler, with current heating oil at 36p / l works converts to 4.2p / kWh. So, using 5.75kWh ‘free’ PV generated electricity per day, instead of heating oil, would contribute £88 / year.
Inching our way forward
Just found out from Green Energy that you can only get onto their TIDE tariff if you sign a dual fuel agreement – seeing as the nearest mains gas supply is about 2 miles away, that rules that out. So back to Economy 7 !
When you think about it, if everyone jumps on the time-of-use bandwagon, the big 6 will have to increase their tariff sharpish.
OK back to the head scratching.
So, let’s look at the big picture.
Excluding the standing charge ( a not insignificant £91 / year), we spend around £615 / year, which I am also going to assume is fairly consistent month-to-month.
If we add the water heating (£88 / year) we get to £700 / year
My Battery Challenge 