Thank you for your thoughts, I guess I started off thinking I only need a small system to offset my home office, (it annoys me that I pay for the Firms’ electricity, even though working from home saves me loads in terms of fuel and time travelling) its the principle of it! But now the idea is growing legs, what about being able to run a washing machine during the day? Then things get interesting, how about running my evening off a battery?
Any thought of heating the home from PVs with battery storage would not be viable for me and many others I guess but how far do you go?
I see this as a project, to feel good about something, it would be a good idea for me to start looking at loads and usage and try to establish a profile, then consider battery size and the array required to charge it whilst running my basis daily use. I have a fairly limited budget so the smaller the better, perhaps I should try the office off set system and see how it goes?
I may not be much help as I haven’t got solar or battery yet - but have had a share in a wind turbine for 11 years now, and have electric heating (air source heat pump), an EV (and a phev) with no gas or oil heating.
I have spent quite a bit of time this year getting quotes from solar companies, including batteries. We are unusually complex due to the wind turbine, also have shared supply with two lots of in laws (if we didn’t we wouldn’t have been able to share the turbine). With no smart meter I have no access to cheaper overnight charging rates for cars or domestic battery
Our electricity consumption is pretty high with imports in the most recent year (when wind generation was the worst ever) totalling around 14500 kWh - I don’t know what we use from the wind turbine but it may be around 4000-5000 kWh (total generation average around 21000 kWh pa of which we get one third). The cars are about 5000 kWh of charging, the ASHP uses about 3000-3500 kWh a year and we have an everhot range oven that is ludicrously thirsty at 4000-5000 pa. The house is well insulated with heat recovery ventilation system
As far as I can tell there is no such thing as a simple way to calculate how much battery it is worth getting. I have seen it argued that it should be enough to cover daily average consumption. But that would be 30 kWh (excluding the cars) for us which seems high. Many people when challenged on this say “what do you mean payback? You don’t calculate payback on a new kitchen or tv so why solar power / batteries?” Which is just an admission that it doesn’t make financial sense so they duck it - although that was before the latest increases in cost.
If you have a cheap overnight rate you can use batteries without solar (or wind) to charge on the cheap for use the next day. With solar you can cover daytime consumption up to a point without batteries. Having batteries smooths things out though and matches generation and consumption better - reducing exports and imports. As we have wind and want to add solar we should be able to get the most from a battery so that if anyone can make a profit we should be able to
As a generalisation you will on any given day generate either too much or not enough energy from solar - in the winter not enough. Summer too much. Rest of the year who knows. Winter solar generation is I understand maybe around 20% of summer levels. It’s the reverse for wind - but we have too much generation on the windiest days to be able to use it all - our share would be around 70 kWh on the very windiest days, but on still days zero
In the coming years, things will I think develop so everyone is on different rates depending on time of day. Vehicle to home will become big (assuming you have a suitable EV), and there will be increased incentives - the bbc carried a story last Friday saying reducing consumption at peak times would get a credit of £3 per kWh saved (octopus and e.on). We cannot benefit from that sadly but with a smart meter we would have a chance and with batteries you could make sure you got the max benefit
You are best getting at least one person in to give you a quote, but by all means ask away here, although it would help us all if you could answer a few basic questions such as
How do you currently heat your house?
Any plans to move to a heat pump in the near future?
Ah, yes I see your point although my neighbour did this and although they seem to have carried out their work reasonably well, their idea of an analysis was laughable. He has more electricity than he knows what to do with and his system dumps his nearly full battery store each week.
I do agree with everyone so far I need to get a grip of my electrical loads including electric hot water heating which would be possible. I was just wondering if their was a good app which provides a nice means of loading and analysing the info and estimating things like cyclic loads, fridges etc.
The only thing unusual about my energy consumption is that I recon it must be very low compared to most people because I am naturally very very tight!
I think the system dumping more than is consumed to the grid isn’t necessarily a bad thing, it should mean that as the days shorten a larger amount of the household’s supply is provided.
I’ve got more electricity (on some days) than I can use and on others far less than I need/want!
For example,
Weds I consumed 16.7kWh and exported 4kWh.
Thurs I consumed 6.2kWh and exported 0.3kWh.
With a smaller system I’d have exported less on Weds and generated less on Thurs.
How much electricity do we use/year for the house + an electric car if we buy one: 8-9,000kWh/year
how many panels can we fit on the roof: 22
how much would they generate in a year: ask our installer to run their simulator: 8,000kWhr/year
Okay, fill the roof with 22 panels, an 8kW array
re battery sizing, we adopted a very sophisticated approach, as follows:
How much electricity do we use in a day: 20kWh
If we needed a day’s back-up supply and didn’t use the heavy users - electric oven & tumble dryer, how much would we need: about half, so 10kWh
who makes a 10+kWh battery that will automatically cut over to battery power in the event of a power cut without ANY manual intervention? Tesla.
Okay, buy a Tesla Powerwall + Gateway.
Bonus Time: Octopus Energy has a special tariff for owners of Tesla batteries. It’s called the Tesla tariff.
In return for handing over control of the Powerwall to Tesla, Octopus offers a special tariff. Instead of paying 30p/kWh imported and being paid 7.5p/kWh exported, we now pay 11.25p/kWh imported and receive 11.25p/kWh exported. We have less back-up battery capacity in reserve but the payback on the whole system becomes very short indeed for us - about 4 years on the basis of our calculation methodology (YMMV).
I’m sure that there are much more sophisticated methodologies but these simple, common sense approaches have worked out just fine.
I use Meross MSS310 outlets which meter the electric mostly on TVs and cooking appliances. I also got to grips with base load things such as the BT Smarthub 2, WiFi discs and Ethernet. Also the Naim boxes. I also have SmartThings outlets but they doubled in price so I bought Meross instead at £12.50 each.
Fridges and freezers are pretty constant, although the freezer varies with use more. There are lots of things that use more than you expect. Eco/automatic programs may not be consistent or reliable. Heat Pump tumble driers are great. Old TVs can use up to 260W on some channels.
Air Source Heat Pumps are great particularly if the radiators are upsized to operate at 35C. We still have deal with really cold weather (installed in May). We operate at 40c out of the pump into a heat exchanger. When it can’t cope we will increase the water temperature. In theory at 40c the SCOP is 4.3. So far in October it has used 100kWh. It only heats the upstairs as passive solar and the wood burner deal with the downstairs. With savings our October electric consumption including ASHP will be no more than last year. We used 800kWh of gas last October.
We decided against a Mitsubishi Eco Dan ASHP which is so loaded with controls you can’t just run it at a fixed water temperature. Weather compensation is not really needed and if parts become scarce you are stuck with a bigger bill.
Finally some spring weather in Sydney and pleased to note that today we produced 45kwh of solar energy - a record day for us since our panels were installed last April , and we managed to consume 32kwh of that solar as we heated the pool.
Our installers forecasted an average of 29kwh for October and a peak in January at height of summer of 32kwh per day- so really pleasing to see this 45kwh generation today.
That’s really good to see. We’ve had 3 days over 40kWh this week and it’s really nice to see figures like that after a pretty poor solar period since we started. I’m glad we went with a larger array as you recommended, so thanks for that. We could probably fit another 2 panels in, but it’s probably no worth the effort unless we do it with adding a battery later on.
My pleasure - glad you are reaping the benefits, I think your right probably not worth fitting two more panels in isolation, our roof would accomodate 4 or 5 on the west side ( all ours are north and east at present) but the roof alignment isn’t straightforward so the layout of the panels wouldn’t appear tidy and thats our street facing roof.
Sun is out again for the next few days in Sydney- so thats good news
Natuarally as soon as it was installed the weather took a turn for the worse but we can already see some tangible savings from our modest 3KW system. Even when cloudy our base load is mainly being covered from dawn to dusk. An Eddi will hopefully arrive in the next couple of weeks which will allow us to divert surplus power to the immersion heater.
One aspect that concermed me was any potential impact on the HiFi. In particular we had to compromise on the wiring slightly which could have cuased issues.
The dedicated radial for the HiFi comes out of a Henley Block to a small consumer unit in the outside meter box. The cable from the HiFi consumer unit then runs outside and into the sitting room where the HiFi is located.
As our main consumer unit inside the house is ‘land locked’ it wasn’t possible to run the cable from our garage where the panels are located to the consumer unit without digging up the floor in the house. Therefore as a compromise the feed from the panels had to go into the HiFi consumer unit in the meter box outside.
I’m delighted to say that there seem to be no ill effects from doing this and the system sounds as good when we’re generating electricty to when we are not.
My 500PS has always been prone to humming. The ASHP quite often brings it on. Doesn’t affect the SQ.
I now have an electric monitor which tells me the voltage and power factor as well as power and energy used. I have seen figures as high as 248V. The DNO say it’s within spec and indeed it can be as low as 230V. Everyone will have variations- it’s just the way the local distribution network works.
Yesterday my installer came back to say the DNO wouldn’t allow me to connect the Powerwall and the inverter must limit output to the grid to a bit below 4kW. National Grid recently took over Western Power Distribution so perhaps that is behind it because there is very little Solar PV on the overhead lines to the substation. They obviously don’t want to spend their money to upgrade the local network if they can avoid it.
According to my installer the inverter will phase shift when there is a lot of PV to dump. I can have a 5kW inverter with the SolarEdge battery which is DC coupled and uses the PV inverter when drawing from the battery. I suppose I can then discharge the battery at the permitted rate at peak hours or whenever it is most lucrative if there is such a thing in the hot weather. The EV is also there to absorb energy so we might just get out and about for the day and then charge from the Solar Edge battery overnight. Good job it’s unusual for the sun to shine relentlessly in the U.K.!
I’m coming to the conclusion that the ASHP normally only uses 6kWh in milder November weather for DHW and CH. It’s the dark wet days that need more. I think two SolarEdge batteries providing 20kWh would deal with the summer peaks of production and the winter needs to power the ASHP with cheap nighttime energy from the grid. The daily average for this month has been 16kWh of which 6kWh is for the ASHP.
The question on battery size is how are you going to charge it in short winter days?
This month I’ve seen solar production between 4 and 21kWh (last month 6 and 30kWh), so nowhere near enough to power my use. However since I can guarantee a purchase price of 7.5p/kWh by charging off-peak I’ve been doing that to about 75% of the battery capacity and letting the sun top up the rest, it doesn’t always manage to (and on other days it massively over-produces hence fitting a diverter to heat water before exporting).
Mostly my 5.6kWh battery has almost managed to avoid purchasing much, if any, peak-time electricity in the afternoon/evening (depends on what we cook).
The idea that you can charge the batteries then sell to grid at the best price in the summer (I guess something like intelligent Octopus?) is interesting but I suspect it would need a lot of manual use or a level of technical ingenuity and integration that’s beyond my ken!
Were I buying again I’d be tempted by the larger battery option but I’m really not sure it would do much except let me time-shift usage in the shorter days so I’m buying off-peak and consuming peak.
With an appropriate tariff, solar panels, battery storage and a solar diverter I’ve managed to reduce my electricity bills by a significant sum (by 75% in October and so far in November) even though I’m only roughly 40% self-sufficient. I’m not sure that the larger battery would have really paid for itself, but would be ‘nice to have’.
Of course, if the 7.5p/kWh price is withdrawn I’ll have a much harder think about storage but even then I’m not sure it’s going to be cost-efficient.
At the moment I’m just not convinced that a large battery makes any financial sense.
The SolarEdge battery has lots of options based on seasonal profiles. I’m hoping it can deal with what I want and that I can fathom how to get it to do what I want. Clearly in summer it won’t need to charge at night if there going to be lots of solar, but I will tell it to discharge to the grid. Conversely in winter I will charge from the grid at night.
I see the battery as a means of time shifting imports and exports.
How are you feeling about your Powerwall and the Tesla tariff after six months. My DNO is limiting me to 3.68kW of export so time shifting particularly in winter is appealing with a 12p/41p GO tariff rather than a flat rate 34p tariff. So whereas the four hours would put 30kWh on the EV, I can add another 19.4 if I fully discharge the battery. In winter the 19.4kWh and some solar should be enough for domestic use including the ASHP. It also means I can export more rather than dumping it in summer.