scdoubleu
Member
Without an offpeak period it makes no sense to charge at peak rate only to discharge later to the house. You’ll lose about 10% due to round trip efficiency losses.
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Solar Panels UK - is it worth it?
- Thread starter jdwuk
- Start date
Winter maybe. But do the math - cheap off peak usually means higher peak. Summer you shouldn’t use much grid anyway.
will off peak and 9.5 get you through most of the day? If so it can be worth rolling up to 100%, limited solar will help a bit, and the combo may get you back to the off peak period. In that case the higher peak rate won’t matter and you’ll benefit from the off peak rate. If you stay on your flat rate you *will* use that overnight in winter as solar alone won’t cover you.
Chimpy McChimp
Member
Chimpy McChimp
Member
Thanks for confirming my thinking. Still figuring out the set up so not sure if I can set the battery to only charge via solar (and If so... How!!!)
Edit: looks like it is set to only charge via solar (in settings) but it clearly charged from grid yesterday. Huh?
Hopefully givenergy customer support is good because the installers were OK but clearly in a rush to get home when they walked through the app etc. Which was almost pointless as there was no data in the system to review at that point)
Wondering if I will ever have enough solar during summer to charge battery and run house. We are very high usage (damn Hot tub!) So need to figure out what our system will generate. Fully expect in winter that there won't be any excess solar to charge battery.
Almost feels like the battery is unnecessary for me at moment until I change my tariff and get a cheap overnight. But.... It was part of the package and interest free loan from Scottish govt. So made sense to buy it now.
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initial grid use may be commissioning - they do a full charge/discharge cycle. Same if you do a firmware update.
how much do you use during the day (do you run the hot tub 24/7??) a decent summer day should give you enough excess after charging the battery back to full, to cover your house load with a 5kwp array I'd think. Then your battery only needs to cover end of sun to your off peak, or end of sun to start of sun.
depending on usage I'd definitely at least estimate costs with off peak - it gives you a stepping stone so you don't have to get through as much of the day on battery only. Instead of getting from eg 7pm to 7am (12 hours) it only needs to get you to maybe 00:30 (half as long) and then a few hours again at the end of off peak until the sun takes over your baseload
flat rate - less fuss about planning battery charge, anything not covered with solar/battery will be charged at that flat rate. Winter time more expensive to fill up battery but then you don't need to bother - all your usage will be eg 30p/kwh
off peak - small amount of planning (really not much more than setting battery minimum to eg 100% in winter, maybe 75% in spring/autumn). Risk is a miss during peak time will be more expensive than your flat rate, but you're charging up at maybe 9p/kwh saving 2/3 cost per unit every day.
how much do you use during the day (do you run the hot tub 24/7??) a decent summer day should give you enough excess after charging the battery back to full, to cover your house load with a 5kwp array I'd think. Then your battery only needs to cover end of sun to your off peak, or end of sun to start of sun.
depending on usage I'd definitely at least estimate costs with off peak - it gives you a stepping stone so you don't have to get through as much of the day on battery only. Instead of getting from eg 7pm to 7am (12 hours) it only needs to get you to maybe 00:30 (half as long) and then a few hours again at the end of off peak until the sun takes over your baseload
flat rate - less fuss about planning battery charge, anything not covered with solar/battery will be charged at that flat rate. Winter time more expensive to fill up battery but then you don't need to bother - all your usage will be eg 30p/kwh
off peak - small amount of planning (really not much more than setting battery minimum to eg 100% in winter, maybe 75% in spring/autumn). Risk is a miss during peak time will be more expensive than your flat rate, but you're charging up at maybe 9p/kwh saving 2/3 cost per unit every day.
Chimpy McChimp
Member
Thanks. Still getting head round this. Discovered battery is set to charge from solar only so not sure why it looks like it charged from grid yesterday. Might be part of commissioning? Anyway Givenergy seem very responsive over email so far.
Sorry. I think you might be right about commissioning. Which if so is fine. Currently enjoying watching our solar panels feed house and charge battery and no grid usage. BOOM! take that EDF!
Sorry. I think you might be right about commissioning. Which if so is fine. Currently enjoying watching our solar panels feed house and charge battery and no grid usage. BOOM! take that EDF!
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phil4
Member
I've got a similar sized array, and this "summer" so far, no way it'll cover house use and fully charge battery most days. Far from it.
I'd still say the battery is a good thing... My initial install was solar only, battery added in June. When having solar only, I was always trying to avoid peak use, but also trying to use as much solar as possible. Everyone says, just stick the washing on, stick the dishwasher on etc... but that only works when it's proper clear skies and sun... otherwise clouds come and go, the generation goes up and down, and before you know it you're drawing from the grid for your "free" wash cycle. The battery eliminates that.
It depends on usage of course. YMMV is key. I think we are pretty average - maybe 12-14kwh a day depending if the tumble dryer is used (will get a heat pump one when this dies). A 9.5kwh givenergy and (2.6kwp south + 3.9kwp north) has entirely covered our electric since install in May.
(Other than occasional boost charge for EV overnight)
We aren’t even charging the battery overnight - we set the minimum to 20% and it never gets there so solar is covering overnight through to morning
The only grid I’m using is lag time before the battery reacts which is more than I’d like (about 25kwh a month and £10-12) but for now that’s still a huge improvement
(Other than occasional boost charge for EV overnight)
We aren’t even charging the battery overnight - we set the minimum to 20% and it never gets there so solar is covering overnight through to morning
The only grid I’m using is lag time before the battery reacts which is more than I’d like (about 25kwh a month and £10-12) but for now that’s still a huge improvement
Chimpy McChimp
Member
Highly recommend a heat pump tumble dryer. I'm not sure what our old one cost but our smart display for the meter would shoot into the red as soon as we put it on. Our new one costs us pennies per load. Sometimes it isn't worth the hassle of hanging washing out to dry knowing how cheap it is to run. It's cost us 54p this month and we have used it a lot.
Plus we don't bother sorting clothes anymore. Even really sensitive stuff goes in and is fine.
Plus we don't bother sorting clothes anymore. Even really sensitive stuff goes in and is fine.
I mean - it doesn't cost us anything at the moment, battery covers it during the day, but might during winter
Chimpy McChimp
Member
phil4
Member
It does... but your example of May was good... July and August today have been only marginally better than April here (South Oxfordshire), even thought July had one extra day.
Mines a 5.33kWh South facing array, use ~18kWh per day excluding charging the car, and a 27kWh battery. I don't expect that to be filled, but through July and Aug solar has mostly been so poor that it hasn't even covered the normal house use.
We are around 24-30kwh per day. Higher when we charge the car
wow. Always curoius about breakdowns - I'm part gas (a lot gas my wife might say) so hot water/hob cooking/heating is not electric. So that would go up when I remove gas, but it alwasy seems a lot.
Chimpy McChimp
Member
Our hot tub is probably the main culprit. It isnt heating all the time but when it does we see spikes in usage. We both also work from home so have laptops/monitors etc etc running all day.
When I look at our usage from smart meter our usage drops significantly when the hot tub is off
But we knew that when we bought it!!
phil4
Member
Laptops are by and large about as frugal as you can get. A desktop PC can usually manage 500W without trouble whereas a laptop is unlikely to be about 50W.
right that was my point when chimpy mentioned wfh. Doesn't add much for us.
Guess a hot tub could be like constnatly heating a hot water cylinder but with more heat loss through lack of insulation. Could that be like 5kwh or something crazy every day??
edit: yep looks like it
Chimpy McChimp
Member
Yeah it's definitely mainly the hot tub.
But our load will be higher than average even without it (compared to houses where people are out all day) as 2 of us work from home so 4 monitors, 2 PCs, lights (even in daytime we sometimes need lights on as back of our house is quite dark). Multiple kettle boils for tea/coffee. Etc etc etc Each probably small on its own but adding up
PITA
Model 3 Performance
Interesting topic.
We rejected Heat Pump Tumble Dryers as they're too slow to dry a load.
An inverter condenser dryer is much faster to dry clothes, and in our house the volume of clothes is too much, to be held up with a slow dryer.
With Powerwalls, Solar and Cheap overnight rates, we're not fussed about the cost.
So condenser dryer won.
well you have your lovely givenergy dashboard so you can get nice daily/weekly reports showing your consumption, how much from grid/solar/battery etc. Come back and keep us updated on that as you progress, always good to hear
