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I've been considering getting solar PV installed but I'm now wondering if the money would be better spent on batteries. I want to reduce carbon and also save money. We use between 30 and 50 kWh per day in winter (depending on the weather and if we charge the car). This will reduce in summer but our water heating is still electric.

 

Solar PV - our roof isn't ideal for panels. We're in the South East and might manage to fit 3.5kW facing ESE. There is some shading so we will have the extra cost of optimised panels.

 

Batteries - if we just had a battery we could charge at low rates and use the electricity during the day. A simple setup would use a tariff such as Octopus Go to charge at a fixed time overnight. A more sophisticated setup would link to Octopus Agile to decide the best time to charge.

 

I should add that we currently have a time shifting heating system as part of a trial. This charges heat batteries during low demand periods. The system has some problems so it's possible that we'll reconfigure it at the end of the trial and remove the heat batteries.

 

Should we fit both solar PV and a battery or forget the solar and buy a bigger battery? Or something else?

 

Your ideas and suggestions please ☺️

I think the name of game is to use solar to charge battery with over night imports form grid if needed. Was with Ovo's EV everywhere but have switched to 4 hours at £0.075 kWh. You do need a large battery for winter when low solar. The round trip with Tesla battery is 10% loss. 

Incidentally @M.isterW over the time we’ve had our system, I would now say that solar PV pays back quicker and more effectively than battery storage although the option to charge off peak is obviously a game changer with battery added. 
I think I saw earlier or on another thread something about the losses or efficiency of converting solar to battery and then use which is why I’d recommend solar before battery. 
It’s also why I still hesitate to move my peak use without an off peak incentive although I will look very carefully once our current contract ends

I’ve been pondering this question - with a heat pump the winter electricity use goes up hugely just when the solar output would be at its worst. But charging a battery during off peak times relies on the tariffs being available. If the battery didn’t last the whole day then peak time costs could be astronomical. Probably the best thing to spend on would be more insulation.

I’ve been pondering this question - with a heat pump the winter electricity use goes up hugely just when the solar output would be at its worst. But charging a battery during off peak times relies on the tariffs being available. If the battery didn’t last the whole day then peak time costs could be astronomical. Probably the best thing to spend on would be more insulation.

Agreed - insulation (cavity wall, loft etc), draft proofing is key. You can get battery storage to last a whole day but what isn’t said a lot is the peak output level that you can get - do it’s important to factor that in as well otherwise you might still use power at peak times. 

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