My dreams for a Solar Powered life

Qyburn

Just thinking of this thread over the last few weeks. Our 8.1kWp system has been only making 30 to 60W for a lot of the time, and only for 6 or 7 hours a day. How big a system would be needed to cover consumption without top up from the grid? Then the waste in Summer, when we'd be exporting up to 1,000kWh a month. .

QrizB

Just thinking of this thread over the last few weeks.

I didn't read it as the OP planning to go off-grid, just net grid-zero.

I agree that going entirely off-grid is impractical and economic madness for 95%+ of households, OP included.

I even think HertsLad would be better off (financially and lifestyle-wise) with grid-tied PV, but it's his choice to make.

Scot_39

https://forums.moneysavingexpert.com/discussion/comment/81876327#Comment_81876327

Too little in winter - too much in summer.

And sadly the grid solar numbers pretty much are almost as dire some days / so tend to back up your personal system experience.

As per the domestic solar quandary - such is the now I suspect even bigger grid solar level quandary.

21.5GW total solar - in summer peak sense - butting up against current UK summer demand in the 26-27GW range.

And £10s bns invested in a technology - ultimately at our expense - that wont keep our lights on - our factories operating - and in the "green" nirvana - our home ASHP's heating - in the depth of winter.

All whilst the grid solar operators will of course be protected by their CfD contracts - now term extended 5 yrs - for 20 yrs as of AR7

QrizB

How big a system would be needed to cover consumption without top up from the grid?

Coming back to this for a moment.

If the OP needs 3000kWh for house-and-car, split evenly across the year, that's 250kWh a month. If they also need 2000kWh foir heating, over the four coldest months, that's 500kWh a month.

So say 750kWh for a winter month, like December.

My 2.7kWp solar array makes about 70kWh in a typical December. It would need to be almost 11 times larger, about 30kWp, to supply 750kWh in December.

If it was 11 times larger it would generate more than 3000kWh in a typical June, and almost 30,000kWh over the course of a year; six times more than the OP actually requires.

If the OP was going to do this, and never import from the grid, it would still make sense to keep a grid connection simply to sell the excesss 25,000kWh back to the grid. Even at one penny per kWh of export they'd recoup the cost of the grid connection; at 5p/kWh they'd be in profit by £1000/year.

Of course 30kWp of panels wouldn't fit on their garage roof, would cost maybe £20k to install and would almost certainly need a three-phase supply, so I suspect it's not really practical for the OP to do.

Scot_39

I make Qyburns figures about 20x worse though - efficiency / or rather load factor wise.

3x the array nominal rating for c 1/7th the energy generated.

Could the ops garage and n/s orientation be as poor vs perhaps your more optimal arrangement ?

Thats quite an output difference.

and not sure £1000 is profit - its return on bills yes - given even £20k if financed likeky to cost more in loan interest on a long term loan.

But its an unfortunate trigger word to raise - when it comes to uk energy - high electricity prices and so the now majority view against expense of net zero focus of approach in uk.

Qyburn

https://forums.moneysavingexpert.com/discussion/comment/81876914#Comment_81876914

My figures are recent, when we've had a sustained SE airflow meaning thick overcast for the last couple of weeks. Near to worst case rather than average Jan / Feb. But true self sufficiency needs to ride out the worst case in one way or another.