Home Battery without Solar

[nowty]

Victron (I think thats what you are talking about) is a premium brand, if you can afford it you won't be disappointed.

[Krill]

We have 4 kW of Solar and recently, August 22, installed 10.5 kW of batteries. We've added another 5 Kw battery. I'm charging, on off peak to 80% , and that sees us through till the next cheap session and any solar is just a bonus. The night time charge is about 9 Kwh 'ish now in November, at 14 pence per unit. We have been known to run the dishwasher or washing machine overnight is the weather forecast is rubbish. We are a mean 2 person, pensioner household. With the OP's 8000 kWh per year he's going to struggle during the winter without huge battery capacity.

I'd agree, the other point is if you want to run an oven or tumble dryer off batteries then you really do need to look at the max inverting capacity of a single inverter. I use two luxpowertek inverters in parallel and it's fine but at that point I wonder if Victron is not cheaper and space efficient (I have wall space for four inverters and with the solar PV inverter used three "slots worth". Many people may need to be far more space efficient than this especially if there is future solar PV being considered).

[robl]

We have a 3.6kW sunsynk Ecco now, with 15kWh of batteries from fogstar. I’m very impressed with it, although the setup is a bit cryptic. It hangs off the consumer unit, with a CT on the main tail, and it can push or pull current in to zero the import. Without particularly trying, it gets rid of almost all our peak useage (we charge from PV and Octopus go) - I’m sure a bigger unit could do a little more of it, but I think it’s over 95% already. I know sometimes people run the mains through hybrid inverter - I guess this is ‘UPS mode’, and gives auto resilience to a power cut. We didn’t do that - we get so few power cuts, I think the inverter (+software+settings) is likely less reliable than our grid. There’s also the power limitation if everything must go through the inverter. At present we have a 100A incoming fuse (which is amazing, many countries eg France charge loads for this). If we went UPS mode, I think it needs a 40A breaker before it, and would limit the total home peak draw.

[GarethC]

Has anyone worked out how big a system you would need in order to cover all needs with off peak low carbon electricity including hot water and heating, if switching those to electric, and if that's even feasible? Say you installed a 50kWh system and switched radiators and water heaters to electric. Would be interesting to compare the cost, hassle and carbon impact of that vs other home greening strategies.

[AGT]

I’ve used 51kWh of electricity and gas from 11:30 last night to now, so 50 kWh wouldn’t be big enough for me, but then I don’t plan on going off grid.

However I’m heating a Victorian property, with 4 occupants, 1 working full time at home and kids PC on in the evening etc.

[robl]

It’s a lot easier to run a house off peak if it’s well insulated! We’ve an all electric 1963, 4 bed house, 4kWp PV, upgraded with a truckload (literally) of insulation. I get all the timeshiftable stuff to happen overnight anyway - hot water (gshp), w/m, d/w, breadmaker, car charger. If we buy stuff I insist on the most efficient - but I find family harmony more important than militant eco attitudes to turning off etc.
The 15kWh batt is about the right size for us. The piccy below is from the 3.6kW sunsynk for yesterday - the batt SOC drops from full to 43%, our peak time draw is around 0.5kWh - blips here and there when too many things are on together. You can see the gshp kick in and out, probably on half the time overall. If we get a proper cold snap with no sun then it will likely run out. I don’t intend to get more batts to cover those few days of the year - my aim now is for more solar, useful all year!

[Joeboy]

Has anyone worked out how big a system you would need in order to cover all needs with off peak low carbon electricity including hot water and heating, if switching those to electric, and if that's even feasible? Say you installed a 50kWh system and switched radiators and water heaters to electric. Would be interesting to compare the cost, hassle and carbon impact of that vs other home greening strategies.

I can't help with the without solar part although due to season maybe. We are using 70 to 75 kWh per day from grid and it is minus 1 here today. PV is bringing in about 3kWh per day on top of that due to cloud cover. We heat all the water, run & heat the home, recharge the battery stack to 100% and charge the EV a bit (sometimes a big bit and we go sailing over 100kWh).

We also run the WBS, I'll be completely honest and say that the storage heaters themselves can't bring the whole home up to where we like to be (22 degs) but it will get it to and hold it at 17 degs when its close to zero outdoors. At that point I am running the SH system at about 65% potential load. The WBS does the rest.

You also have to allow for % of depth of discharge and overspec the size of pack to allow for that. If you have an EV maybe you have consistent access to day charging but can continue to plug in at home to trigger IO?

Also need to think about pack degradation and future expansion to allow for the storage lost over time.

We are about 2,500 sq ft footprint, 5 bed, 3 public etc. If i wanted to go full operating 24/7 on a grid pack offgrid i'd need it to be 100kWh capacity with a simple add on facility of another 50kWh.

Going on the 100kWh for simplicity and using IO & a generic (25p) tarriff it would be daily costs excl SC of

IO £7.50 per day
Generic £25 per day
£17.50 to the good per day.

At the moment though we get by well with a 28kWh pack, a grid connection and can finish the day with a 30% SOC in battery pack.

Love this "I find family harmony more important than militant eco attitudes to turning off etc".

There is also the discipline of actually remembering to timeshift the heavy appliances into the night so the battery can go easy through the day. I'm not always there with that.

[AGT]

I find Robl’s post above with this statement the most sensible and it’s what I try too

‘ I find family harmony more important than militant eco attitudes to turning off etc.’

[nowty]

4 bed 1970's detached house heated to brazil (SWMBO) temperatures for under £1000 a year of grid import. All electric except gas hob and 99%+ off peak. I could probably get by with a smaller 30kWh battery with using a little gas (or more storage heaters) in the rare extreme winter conditions.

All green stuff has been self funded, i.e. used cheap borrowed money to fit solar, batteries, ripple projects and surpluses used to pay back or buy more. A lot of my stuff has been bought cheap second hand and done DIY.

I've been lucky with the timings though, if starting now, cheap money is harder to come by and no FITs anymore. But some cheap credit card deals are still around for card tarting and SEG is worth it.

My advice is,

• Fit a small initial system to get the MCS certificate.

• Get a smart meter and an export MPAN number for SEG.

• DIY with more solar and batteries.

• Incrementally increase insulation where possible.

• Get an EV to get on a decent EV TOU tariff.

• Fit storage heaters and A2A HPs for heating.

• Look into Ripple or other community green generation projects.

• Avoid the red tape like the plague, i.e. don't apply for unnecessary planning permission, etc.

As you go, work out costs and savings and tweek from there. If you do it for financial and for comfort you will pleasantly find yourself green without even knowing it.

[GarethC]

Really interesting. In danger of hijacking the thread here, and if so my apologies and feel free to shut me down.

Nowty, how costly and feasible would it be, in principle, if you'd installed circa 100kWh of home battery and gone all electric, instead of having storage heaters and hot water storage? Would there be a simplicity advantage?

As an aside I'm becoming more militantly eco the more it becomes clear that we've screwed the world for my kids, their kids, and everybody else's kids because we like long hot showers!