Solar PV...Still worth it?

Verdigris

Car sound. Forget the underfloor heating. You won't get the free electricity when you need it, or in sufficient quantity.

You should about 1000kWh/kWp of panels per annum. So if you have 4kWp of panels (an "average UK installation) you should get 4000kWh of electricity, mostly in the summer, per year.

Spies

Evade said:

Hello. I’m just starting to think about the logistics and benefits of putting some panels on our large south facing roof. We’re unlikely to move out of this house for ten years or so. We have an electric car. We’re considering electric underfloor heating. I can’t even contemplate how to do the maths, but if we can reduce gas heating to just a couple of hours a day during winter for example, given that we both work from home, and power the car, feels like it would make sense. How do I go about working this out? Thanks

Go on the pvgis on website and work out the yield for each month, without a battery assume 36% self usage in the summer months and 60% in winter then work out your savings by multiplying that by the unit rate. 

arty688

Also if you are on say octopus go and you could charge your car off peak then when calculating the savings of charging your car on a sunny day you need to use the off peak rate. 

So the first question to ask yourself would be how much electricity do you use not including the EV ? 

arty688

Then the second question is when during the year and day do I use this electric ? And can I shift it to daylight hours or off peak hours.

Petriix

Spies said:

Evade said:

Hello. I’m just starting to think about the logistics and benefits of putting some panels on our large south facing roof. We’re unlikely to move out of this house for ten years or so. We have an electric car. We’re considering electric underfloor heating. I can’t even contemplate how to do the maths, but if we can reduce gas heating to just a couple of hours a day during winter for example, given that we both work from home, and power the car, feels like it would make sense. How do I go about working this out? Thanks

Go on the pvgis on website and work out the yield for each month, without a battery assume 36% self usage in the summer months and 60% in winter then work out your savings by multiplying that by the unit rate. 

With an EV + Zappi and working from home we manage to self-consume ~ 60% of our generation.

To calculate your ROI I'd work on the assumption that you will use about 2,000kWh of whatever you generate and export the rest. So, at the current cap, 2000 x 20p is £400 saving per year plus say 2000 x 5p SEG payments is £100 so roughly £500 per year return for a 4kWp system. If you pay £4k then that's 8 years at current prices.

arty688

Unfortunately not that simple , it will depend on the tariff you are on. Me for example an on octopus Go and pay 5p off peak 15p peak . I charge the car off peak atm probably about 10kwh per night if I were to charge with solar I would only save 50p not £1.50.I would say £5k is more realistic these days for a 4kw and self consumption around 30% peak if no battery and using a TOU tariff. 

Could still make sense I just depends how much electricity that you can’t move off peak you will use between say March to September. 

One the plus side for pv prices of energy seem to be only going one way.

arty688

with solar I would only save 50p not £1.50

bit of a miscalculation forgot about SEG @3p

so should be 20P not £1.20

Spies

In December, even though it was a very dull month, I saved £8.45 in energy costs (42.24kWh*20) and made £4.67 back from SEG and that's typically the worst month of the year,

QrizB

Spies said:

In December, even though it was a very dull month, I saved £8.45 in energy costs (42.24kWh*20) and made £4.67 back from SEG and that's typically the worst month of the year,

Agreed, I've got a smaller array but still saved (34*15.6p) £5.30 on electricity that I would otherwise have imported. (My export is deemed so there's no fair comparison to be made on that side.)

arty688

Spies said:

In December, even though it was a very dull month, I saved £8.45 in energy costs (42.24kWh*20) and made £4.67 back from SEG and that's typically the worst month of the year,

Although saving do heavily depend on your tariff for instance me on Go would have saved £6.3 on used and from the SEG of 3P not earned much I guess.

But with a few days in December over the 100Kwh being on Go is far better than the standard tariff.