Most efficient way to use solar?

YorkshireJames

markin said:

Im not sure if you should be on economy 7, you should do the math on if you should be on a normal tariff, The heating will be running almost 24hrs not just at night, You may even end up with a temperature set back at night so are using less power at night than day, unless the summer solar makes up for winter day costs, and you charge an EV at night in summer?

And look at going with octopus agile

https://www.energy-stats.uk/octopus-agile-outgoing-export/

That's interesting. The £1+ per unit export is very high! I was looking at batteries and this article was talking about how powervault batteries are optimised to use octopus agile to buy from the grid when its cheap and sell it back when it's highest (in the day):

https://www.solarguide.co.uk/solar-batteries/powervault-g200#/

If the battery was buying at 5p per unit and selling at £1, it would more than pay for itself over 10 years.

YorkshireJames

I take it back now I've looked closer at the numbers.

Buying at 7.5p per kWh and selling 3.2kwh (4kwh at 80%) at 35p per kWh, that's only 88p per day.

25p standing charge brings that down to 63p. Over 10 years that's £2,300 - so a £5k 4khw battery doesn't break even.

That's with no solar.

Petriix

YorkshireJames said:

I take it back now I've looked closer at the numbers.

Buying at 7.5p per kWh and selling 3.2kwh (4kwh at 80%) at 35p per kWh, that's only 88p per day.

25p standing charge brings that down to 63p. Over 10 years that's £2,300 - so a £5k 4khw battery doesn't break even.

That's with no solar.

It's more about buying at 7.5p and using to avoid importing at 30p. An 8.2kWh battery for £4k saving 22.5p (at 90% efficiency) is £1.66 per day, £606 per year, < 7 years ROI. That's before you consider storing and using your own solar as well. You might have to consider that saving at 7.5p minus your SEG rate (not for those of us on deemed exports) but it all adds up.

The unknown factor is the longevity of the cheap overnight rate. As long as there's a large differential the batteries will look like a good investment.