Talk Morgan Forums Community The Malvern Arms Is your PV solar array generating more

Tim,

we use about 7200kwh a year, we generate about 4000kwh and get paid 56p/kwh for doing so. So we generate a bit more than half we use.

Peter

That's amazing, I'm quite envious. So on a day like today the more you're exporting to the grid the more money you're making. We do the opposite, anything we export is seen as a waste so we try to balance generation with consumption and use the batteries to spread the consumption across the day so we use every scrap of solar output we can.

Tim,

We don't have to export anything to get paid... the Feed In Tariff is simply a payment for Generating.... it is assumed that 50% is exported, the payment for that is much less. It is a 25 year, index linked, untaxed payment that started in November 2011. Since then we have generated 34,477kwh.

We have a 3kw battery pack and a device to turn the electric immersion heater on when the we are generating more than we are using.
The best bit is that the annual income from the Feed In Tariff and export tariff together cover the full cost of the electricity and gas we use.

As I type we are generating at just under 2kwh, the "Smart Meter" display shows that we are buying no power from the grid.

Peter and Tim, I am curious as to what is the payback period for your installations and are there maintenance costs that have to be included in that costing e.g. new batteries, panels, etc? I realise the costs can be somewhat subjective dependent on the system/consumption, we have over 300 days of sun a year and are South facing so an ideal candidate but would have to convert the house from gas to electricity which is quite a cost to add.

Bruce it really depends here on the government subsidy to produce power. The scheme was very generous but lately has reduced. So when I moved the FIT fell from 45p / kWh old system to 4p / kWh on a new system. You also get 5p /kWh for export (the power companies assume you export 50% of what you make).
The other varianble is what you buy power for , I am pay 18p /KWh but in April that will jump on contract renewal.
I also have a device to divert power to heat hot water. That has saved 2,500 kWh roughly, but we would otherwise heat water by gas which is cheaper than electricity.

My 3.9kW array cost £5,500 is Dec 2018. We have since generated 8654 KWh of power.
My estimate is roughly 6 years payback, but of course power prices will only climb & at best you can get 0.5% interest on cash.

I hope that helps a bit.
John

Hoping to move into a new bungalow shortly. This has heat pump powered under floor heating and 12 pv panels on the roof. Was expecting 3+kW with such an array but electrician doing first fit reckons they are low power ones and to expect around 2kW. Guess its the minimum the builder could install to benefit from government incentives. No feed in either, apparently tariffs so low nowadays its no longer worth it. Big hot water tank so that will be useful dump of excess power although not sure what programming is possible.

I've experience of pv power generation on a sailing yacht having installed 2 x 150 watt panels myself hooked up to mppt controller, but home systems will present a new learning curve for me.

I have no FiT contract or Smart Export Guarantee scheme (its successor) payments, so the payback calculation for our system is not brilliant.

We paid a smidgeon over £33k for 2 installations giving a total maximum output of 9.6KW and 14KWh of storage capacity, with an estimated generation of around 9000KWh/year. There's a 25 year guarantee on the panels and 12 years on the battery (including labour) with free remote management and software upgrades.

If we use all the generated power ourselves a projection based on £0.20/KWh rising at 2%/year (average UK inflation) then we end up with a 15 year payback - but of course we won't be able to do that, in the summer we'll have far more power than we use. If we cut the usable output down to half, ie 4500KWh/year then it's a fairly nonsensical 25 year payback.

BUT (and it's a big but) - the energy inflation rate is much higher than the average, it's been 5% for the last 5 years, and I have no confidence it's going to fall any time soon. So plug in a 5% inflation rate into the calculation and you get a payback of 20 years - which is a bit more palatable. If the UK messes up its energy strategy (quite likely) then I wouldn't be surprised if we get higher inflation figures as we run out of generation capacity (nukes going offline and nobody building replacements).

Either way as I said it's not brilliant, but what the hell, we aren't doing it for the money.

Ah yes, I was confusing it with the SEG payment which is on actual KWh exported rather than the 50% of capacity that you have.

Richard,
if the move goes ahead then let me know if you need the details of our auto switch system to heat the water. Our from memory kicks in once we start exporting over 250W. The house background usage on fridges etc is around 100-150 W
John

Bruce,

when we bought the system in 2011 we opted got the more expensive "high efficiency" panels from Sanyo. They, the inverter and installation were £15,234. They reached payback in September 2019. The later battery pack and inverter was £4,500 and comparing 2018 with 2020 consumption of electricity I'm not convinced it was a good investment, the payback seems to be about 10 years, although if as Tim predicts electricity costs go up the payback may be shorter. I will not be adding any additional batteries, at the moment!

The panels are still generating at more than 90% of their specified output, despite not having been washed.
The Inverter was estimated to have a life of 10 to 15 years, but it is mounted on a NE facing wall that gets no sunlight, so it will not be heat stressed. So far, so good...