PV benefit in the day / cold months

NoobSolar

Hi everyone - this is for experienced Solarists to give advice to those awaiting install on the benefits. Is there any point putting the delay timer on my Washing Machine /dishwasher in the winter months, the better to catch a few rays and save some costs? Or would it be a negligible benefit?

JKenH

That depends how much spare generation you have. Do you have a smart meter to see what you are consuming/sending to the grid?

The problem with dishwashers and washing machines is that their consumption has peaks and troughs as the heating element kicks in and out. You can find one minute you are pulling 1kW from the grid and the next you are exporting 1 kW. When solar PV levels are low I prefer to use something that is more consistent in terms of consumption. 

EricMears

NoobSolar said:

Hi everyone - this is for experienced Solarists to give advice to those awaiting install on the benefits. Is there any point putting the delay timer on my Washing Machine /dishwasher in the winter months, the better to catch a few rays and save some costs? Or would it be a negligible benefit?

Everything depends on your tariff(s) !

If your cost/impkWh is the same throughout the day then yes,  it would definitely save something if you run major appliances when you expect to be exporting (which of course is only when generation exceeds background consumption).

If (like mine) you're getting FIT payments then you'd save the full cost of any units you can avoid buying.  OTOH if it's a new installation you'd only be saving the difference between your import ppu & export ppu and with some export tariffs that might even cost you extra !

If your imports are on a variable price tariff then at this time of year you'd probably make a bigger saving by running major appliances when import costs are at minimum.   e.g at height of summer we'd probably run dishwasher just after lunch;  this month we're running it after 8:30pm when our Octopus GoFaster tariff means we pay only 5.5ppu.

Spies

In my experience its difficult to take advantage of it unless its a completely cloudless sky, the washing machine for example doesn't heat its water until about 20 minutes into its cycle, at which point the sun could have gone behind a cloud! Similarly with the dishwasher, it does a cold rice cycle first. 

Merlin139

We do sometimes put our washing machine and dishwasher on timer delays during the winter months.

The biggest one for us is the weather forecast for the day or the following days. On the 9 sunny days we have had this month we have been generating 1.5 kW and above from 10:00 till 13:45 on 7 of those days, so its worked out well. But in December that only applied on 4 days of the whole month. Having a South facing system really helps. Any spare generation goes to Iboost so happy either way. 

If its meant to be sunny then we will schedule it. More so for the washing machine than dishwasher. 

The biggest thing for us is finding sunny days to do the ironing! 

Verdigris

it does a cold rice cycle first.

I want to know when it does the egg fried!

Martyn1981

Short answer negligible.

Long answer - Personally I'd file this one under - don't worry too much about it. If you get into a habit of checking the weather forecast, as Merlin suggests, then you will find times when you can get away with it, or let's say, benefit a bit if you are flexible on the time/day of use. But overall, very small gains.

Pedancy alert now - The question is actually more complicated than you may have realised. Generation in the winter is lower, so a large system may be fine, but a small system, a no-no. Then you have to consider orientation, south facing will give you some good gen around midday if the weather isn't awful, but E/W (like me) will struggle to achieve high power Nov through Feb.

And (tongue in cheek a bit) it also depends on the term winter. I think meteoroligist use Dec to Feb (three coldest months), all poor months, but the astronomical* definition would be from late Dec (winter solstice) through to late Mch (spring solstice), and by late Feb / early Mch gen is picking up strongly.

*I actually wrote astrological first by mistake, now that would have made the subject interesting! 

Verdigris

One benefit of winter sunshine is that cooler panels have a higher efficiency, so you get more bucks for your sunbeam!

paul991

if  your  using a  diverter to heat your  hotwater,it  may possible to get a dual fill machine  or  just use timer to make use of economy 7 

EricMears

Martyn1981 said:

*I actually wrote astrological first by mistake, now that would have made the subject interesting! 

If you could find a really accurate 'crystal ball',  you'd be able to schedule your power usage pretty well (but of course with repeated lottery wins you wouldn't need to bother) 

Exiled_Tyke

Martyn1981 said:

Short answer negligible.

Long answer - Personally I'd file this one under - don't worry too much about it. If you get into a habit of checking the weather forecast, as Merlin suggests, then you will find times when you can get away with it, or let's say, benefit a bit if you are flexible on the time/day of use. But overall, very small gains.

Yep. Agree with this.  At this time of year my very best output peaks at about 750W but only for a very short time. By the end of Jan it gets to 1kW but again for so little time - and only if the best time point of the day (early afternoon for me) also happens to be the sunniest.  So after the house base-load is covered the amount left to benefit a well timed wash is indeed negligible.   

Of course move forward a couple of months or invest in a battery and the whole story changes..........