New Solar PV Installation

scorp_a

Anyone using SOFAR inverter? Not sure if this is better/worse than Solis.

scorp_a

some details from the 4th Quote(6.3KW system). Is their monthly estimate realistic?

Martyn1981

Prepare to get obsessed and loose 30 minutes playing around!

Try PVGIS, it's a great tool, I stuck a pin in Oxford (just for an example) and changed the system size to 7, clicked 'visualize' and got 6,900kWh, that's 986kWh/kWp so not far from your 1,022 per kWp quote, and a similar monthly spread.

scorp_a

Is there any disadvantage of going with higher rated panels if there is roof space? 
Particularly looking at JA460W panels. 16 of them would give me 7.3KW.  

Coastalwatch

Can't think of a disadvantage, apart from cost. Generally the bigger the better, providing you can get permission form the DNO for it. Option 2 looks good value of those quoted. With the higher rated panels working out £1150 more for an additional 300Watt's, I think I'd struggle to justify them. But of course the choice is yours entirely.

Hexane

If you're going to be selling surplus electricity back to the grid, it's hard to see how a iBoost can be worthwhile. By diverting electricity to heat water, you're losing out on the money you would get for selling that electricity, which means you're losing more than you're gaining. (Unless your usual methods of heating your domestic hot water are very expensive.)

Ectophile

Hexane said:

If you're going to be selling surplus electricity back to the grid, it's hard to see how a iBoost can be worthwhile. By diverting electricity to heat water, you're losing out on the money you would get for selling that electricity, which means you're losing more than you're gaining. (Unless your usual methods of heating your domestic hot water are very expensive.)

That depends on how the export tariff compared with the import tariff.  I was under the impression that the energy companies charged retail rate for imports, but wholesale rate for exports.

Petriix

If you have a gas boiler then the iboost will actually cost you money: 2.5p/kWh of gas at 60% round trip efficiency =  4.16p/kWh of heat vs 5.5p/kWh for exported electricity.

Hexane

Ectophile said:

Hexane said:

If you're going to be selling surplus electricity back to the grid, it's hard to see how a iBoost can be worthwhile. By diverting electricity to heat water, you're losing out on the money you would get for selling that electricity, which means you're losing more than you're gaining. (Unless your usual methods of heating your domestic hot water are very expensive.)

That depends on how the export tariff compared with the import tariff.  I was under the impression that the energy companies charged retail rate for imports, but wholesale rate for exports.

If his usual methods of heating his domestic hot water are to use an electric immersion heater, with no recourse to gas, oil, heat pumps, Economy 7 or any other alternative, then yes that would count as "very expensive". Such a setup would be quite unusual, and saving money (and carbon emissions) would probably involve resolving that problem first, rather than spending money on solar panels but leaving the DHW issue in place.

Like many others, I'm not on metered export, so I heat my DHW with an iBoost-equivalent, supplemented by gas central heating when necessary. As a new install without FiT, the proposed system under discussion here will have metered export, if they want to sell their surplus which they surely do. It is puzzling that installers keep including iBoosts in quotes without explaining the financial realities - as Petriix says, in most new install circumstances, an iBoost will lose money for the householder. I wonder how the calculations on the quotes explain this...

Coastalwatch

While I appreciate this website is a principally a money saving tool, accelerated global warming is clearly demonstrating it is a threat to the very existance of human life on this planet so making judgements based purely on economics and ignoring sustainability could be considered short sighted at best and maybe even reckless otherwise. Take your pick!

In case it assists the poster in coming to a decision on which system to adopt, I put some figures below of our journey to emission free energy consumption including the purchase of the largest pv array our roof would accommodate, 8.85 kW.

With full GCH, rads, hot water and gas hob in 2017, our first full year of occupancy, we consumed 8901kW of gas and with no pv, consumption of leccy was 2404kW so totalling 11305kWh's. Circa £906.

Since then we've installed a pv array, purchased an EV and gradually decommisioned all gas appliances. Apart from three months use of gas for cooking only, 2020 will be our first full year reliant purely on renewable leccy. Being three quarters of the way through we've so far imported 2402kWh's. There are three heavy months of import still to be added. If last years figures are anything to go by then these may amount to 1232 kWh's so making a possible total of 3634kW's of import. Circa £635 plus £64 for 3 months gas(incl 9 months S.C's)

So far 948 kWh's has been for space heating(2 x ashp's) and 304 for the EV or approx 50% of all that consumed to date.

PV generation typically 9500/yr so approx £260 received in export and approx £800/yr saved in not having to purchase the dreaded diesel!

The array covers all our domestic energy needs and approximately 75% of motoring mileage/year. Naturally import is unavoidable in winter when consumption is heaviest and generation weakest but hopefully the above figures give a flavour of what the future may hold given the opportunity.

We don't have iboost but certainly something to be considered as it's especially useful in the shoulder and winter months.