I've been doing a lot of research recently into solar, battery storage and electricity tariffs. I plan to install a new system at home to work with my electric Aga cooker. Why do I want to do this? 4 reasons.
- I want to reduce my emissions. No, the world is not ending but long term must shift to sustainable sources of energy as far as possible. The 'long term' eventually arrives, if not for me then certainly for my little girls who are 1 and 4. I want them to live in world of abundance and light powered by cheap green electricity.
- I want to save money. Using a combination of solar power, variable electricity tariffs and a battery I can massively reduce the amount I spend per kWh or electricity.
- I want to have a margin of safety from the grid. Even though the grid is more reliable then ever (more info here) it will be nice to be insulated from the effects of power cuts!
- I'd like to cool my home in the summer. Air conditioning is very much a luxury in the UK but I'd like cool bedrooms and to occasionally cool other parts of the house when it is super hot. Doing this powered by the summer sunshine means I don't have to feel guilty about it!
As I have an Aga cooker that runs on electric I use an above average amount of power compared to most UK households. In the winter it heats the house of course (none of the heat escapes up the flue like with fossil cookers) but there is no getting away from the fact that I use more than most. That is why the gains from installing a solar + battery system are that much bigger. The return on investment is higher.
As a great example of this my friend Mark, an early adopter of solar + battery tech, paid 9.35p/kWH for his electricity from the grid in March. I paid 29p/kWh, roughly 3 times more! That he pays less overall is because his battery automatically charges itself from the grid when electric is cheapest, overnight and into the really morning. It then discharges (is used by his home) during the day when prices are higher.
My aim is to at least halve my electricity costs over the year from £2,500 (10,000kWh at 25p/kWh) to £1,250. My Aga cooker (a 2 oven Blake & Bull cooker using the eControl system + Instaheat hob) uses 4200kWh annually at a cost (from June) of about £1,034. Oil cookers cost about £2,400 annually and gas about £1,900 (both including servicing).
A 6kWh solar system should generate 5000kWh annually and combined with a small battery, 8kWh, will allow me to 'shift' that power to when I need it. Too much solar and too big a battery becomes inefficient as selling power back to grid is worth so little money (only 5p/kWh).
Battery sizing: the optimum battery size is governed by whatever is the lower - your average surplus solar PV generation per day over the summer 6 months OR your electricity consumption outside sunshine hours (i.e. 6pm-8am) per day during the summer 6 months.
With this system my consumption of generated power would be approx 90% (10% exported to grid) and self generation of electricity requirements approx 50%.
The cost of this, on my 3 bed semi detached 1930's house in Bath should be around £10-11k. I'll let you know when I have the full quote! There is no VAT now on the installation of these systems. A huge and recent change.
At £1,250 saved annually that is up to a 12.5% return on investment. Thats far better than any savings account! I actually think I can do better too as hopefully the electricity I do buy from the grid each year (approx 5000kWh) will end up substantially cheaper than the standard rate assumed here of 25p/kWh. If it ends up at 9.35p/kWh my annual bill would be just under £500! Fingers crossed!
In environmental terms the return is much higher. By charging the battery on solar or at cheap times (normally this is when the grid is very green and the wind is blowing or sun is shining) almost all of my consumption over the year can be from low or zero carbon energy. On top of this I am insulated from power cuts and can cool my house guilt free in the summer using air conditioning units.
I've done a lot of research purely as a consumer (I have no commercial contacts in this area) and would recommend talking to Powervault about all this. They design and make the batteries and software needed to make them talk to the grid and charge at the best times etc. I'll keep you up to date as my journey progresses, let me know if you've done anything similar to this and have any advice for those considering it too!
