Free solar power system. Is it a scam?

keith_r59 wrote: »

However, from a personal point of view, if I had a choice of similar houses in the same street I wouldn't buy the property with rental panels installed on the roof especially if it was more expensive than the one which didn't have them.

I'm of the same opinion.

For those determined to have installed solar panels on their next house in the coming years, the relative attraction of a house with a purchased system (with no lease assigned to the property, and attracting fits of around an index linked £1200pa, together with a small reduction in their electricity bills) seems overwhelming compared to a house with a 'free' system (with the complication and obligations of a lease, and just a small reduction in electricity bills).

If the 'free' system had the benefit of a reasonable buyout clause, then the situation wouldn't be too bad, but if there is no buyout clause, it's very possible that buyers would be put off and look elsewhere.

anxious_mum wrote: »

The representative explained very well that, on a sunny day, if you have a dishwasher, washing machine and tumble dryer on all at the same time, you will easily use up the power generated by the panels, but if you re clever with how you use your appliances you should be able to make considerable savings over a 12 month period.

I've gone for it anyway, if anyone is interested how I get on I can re-post in the spring when they have been fitted.

By all accounts the ASG system is one of the best 'rent a roof' systems.

Their large systems are 3.3kWp and should produce around 3,000kWh a year - the minimum they expect is 2,800kWh I believe.

I suggest it is far more difficult to be 'clever with the use of appliances' than most people envisage.

The output of the panels will vary from about 3kW on a sunny summer midday to zero, and 'matching' usage to the generated electricity is almost impossible.

I suspect few people will be able to use more than 1,000kWh a year even if they are home during the day.

noncom wrote: »

Why is it difficult to be clever with the use of appliances? Both my washing machine and tumble dryer have a Delay Start facility, which means I can load them in the morning before I go to work, knowing that the washing machine will set off about 11am and run for an hour, then the tumble dryer will come on about 1230 and go for however long that needs.

It's also very easy to have a timer switch on a multiway mains socket so that all our laptops charge up around in daylight and then we can use them off battery in the evening.

I can also do the same with the slow cooker so that it comes on around the time we start generating and makes me a lovely casserole before the sun goes down.

My system's new, so I don't know how much all this will save, but it will achieve something at least.

Timers are great if they can tell you when the sun is shining and consequently generating electric but what happens when you set your washing machine for 11 and the sun doesn't shine until 12? If you're at home you've got half a chance (as long as you don't have anything else to occupy your mind) but otherwise Cardew is right it's not as easy as you might think to be clever with the electric. Slow cookers use minimal electric and tumble dryers use loads of electric at a time of the year when even in full sun you won't be generating much power.

I work from home and have a 3.9kwp system installed but I expect to make my moeny from FiT and maybe make 30% savings on my electrci if I'm lucky. I'm not knocking the free systems but you do need to be realistic with what you can expect to save.

noncom wrote: »

Why is it difficult to be clever with the use of appliances? Both my washing machine and tumble dryer have a Delay Start facility, which means I can load them in the morning before I go to work, knowing that the washing machine will set off about 11am and run for an hour, then the tumble dryer will come on about 1230 and go for however long that needs.

It's also very easy to have a timer switch on a multiway mains socket so that all our laptops charge up around in daylight and then we can use them off battery in the evening.

I can also do the same with the slow cooker so that it comes on around the time we start generating and makes me a lovely casserole before the sun goes down.

My system's new, so I don't know how much all this will save, but it will achieve something at least.

Hi noncom

I agree, there is no problem with setting timers, the problem is the weather forecasting ... when you set the timers do you know that it will be sunny when they switch the appliances on. Using timers for low power devices and using low power devices in gerneral (such as a slow cooker) is the best way of utilising the pv power available, also, most (?) with pv arrays will gain when using high energy units such as washing machines, unless they are on dual tariff electricity, when, on the majority of occasions, it would be cheaper to set the timer for nighttime use.

I think that most people miss the point that is often made by those who maintain that it is very hard to use a high proportion of what grid tied pv arrays produce. Take your example of washing and we'll explore what would happen .....

To keep things simple, lets say that it's a really good day and a 3.3kWp array produces exactly 2.5kW continuously for 1.5 hours. Now let's say that the washing machine is the only device which can draw power in the house, it runs for the 1.5 hours and has a maximum AC power requirement of 2.5kW, made up of a 2.25kW heating element and the motor draws 250W when washing and 2.5kW when spinning resulting in a power consumption for the full cycle of 1kWh ..... the figures are massaged to simplify, but this would be close enough to a typical scenario.

Okay then, from the figures above it can be deduced that within the 1.5 hours in question ....

The solar pv array produced 3.75kWh
The washing machine consumed 1.0kWh
Imported 0kWh
Exported 2.75kWh (73.3%)
Cost of Wash @10p/kWh = £0.00

---

Let's now assume that it's a different day, still very bright, but the array is producing 1.5kW continuously for 1.5Hrs.

When heating or spinning the machine is drawing 1kW more than the array is producing, so what is the effect of this. We know that the background power usage of the machine is 250W and the overall usage is 1kWh over 1.5Hours, therefore we know that during the cycle the machine consumes 375Wh as a baseload and an additional 625Wh either heating or spinning. 625Wh over 1.5 hours means that the average additional consumption is 416W from a 2.25kW draw, so the machine is either heating or spinning for 18.5% (416/2250) of the cycle, therefore about 0.2775Hrs (16.5 minutes).

If my logic is correct, we now have a situation where for 0.2775Hrs we have a shortfall of pv production to demand of 1kW, therefore 0.2775kWh ...

The solar pv array produced 2.25kWh
The washing machine consumed 1.0kWh
Imported 0.2775kWh
Exported 1.5275kWh (67.9%)
Cost of Wash @10p/kWh = £0.028

---

Cloudy day 500W (shortfall 2.0kW) constant for 1.5Hrs ...

The solar pv array produced 0.75kWh
The washing machine consumed 1.0kWh
Imported 0.555kWh
Exported 0.305kWh (40.7%)
Cost of Wash @10p/kWh = £0.056


As can be seen, things become very complicated even when looking at one device running, especially so when it is something which has a variance on power demand, such as a washing machine, therefore 'being clever with devices' to maximise 'in house' use of locally generated power is difficult .....

There wasn't a cloud in sight when I started this post, it's now overcast and snowing ....

HTH
Z

anxious_mum wrote: »

Blimey Zeupater! Can you type more slowly please!

Seriously though, thank you for that info, it has certainly simplified things for me, even with my tiny brain. I think my point is, as I am not paying for anything at all, then any gain is better than none.

While you're not paying for anything, that doesn't mean you aren't potentially losing out. 25 years is a long time, and during that time, you are restricted in what you can do with you roof. Like you can't put up your own panels and get the fit, you can't have a loft conversion (probably), and there's a possibilty that, if or when you come to sell, that a potential buyer may be put off due to the panels and walk.

All those things are OK if your return in the form of cheaper electricity bills make it worthwhile. What sort of savings on your bills are you expecting to make from the panels? Did the salesman indicate likely savings?