Talk Morgan Forums Community The Malvern Arms Off grid and power walls etc

I stumbled across this and thought some may find it interesting with the various approaches to save money.

Our son and his girlfriend have lived properly off grid (no a.c. d.c. or running water and an earth latrine) for six years now but recently bought a house for the future and do get their ablutions there now being sensible people and he has gone to Uni so needs to be fairly presentable at the Eden Project where he studies as a mature student.

Not off grid by any means but we moved just over 15 months ago into a new build three bedroom bungalow with 3kW of pv solar. The home has well above average insulation, air source heat pump, underfloor heating and is all electric. Even our tumble dryer uses a heat pump.

First thing we did was to register with Octopus energy including the solar as they allow a modest feed in tariff which has recently doubled to 15p/unit. Second thing was to move half of the twelve pv panels to the south west facing roof. The architect had specified them all on the south east side and installer had to comply. This was an easy job equipment wise as the inverter had twin MPPT control which loads each bank to hold them at voltage for max power transfer according to light availabilty. This allowed better diurnal use of sun particularly in the summer with the smart meter remote display keeping us well informed. During this season we found that exports were on average double the energy we took from grid. Indeed one monthly electricity bill was just £3.06! This could be offset by the largest bill we received of £199 for January this year which would probably have been a little less if the solar had been operating, having found it switched off - the switch was deep in a kitchen cupboard and had been knocked off accidentally - lesson learnt

Although familiar with pv power having previously installed 300 watts of solar panels on a boat I lived on for several years, its still something of a novelty in our home. We could in the future add batteries but doubt this would be effective financially without upping the solar installation.

Great Job there Richard, I have Solar PV panels on my properties rented to tenants, its win win for me as I receive the Feed in tariff (at its highest rate was around 50p per unit) and the tenants pay a higher rent but receive the bonus of cheap electric. The FIT payments are tax free also, just filed one FIT today 1400 units generated at around 50p unit will give me £700 ish tax free.

I do want to help the tenants with perhaps a solar switch that switches on the electric immersion tank/copper cylinder on when the higher 2-3kilowatt is generated, any recommendations.

I've been a responsible land lord and only increased rents by 5% this year and despite economic circumstances do want to look after those in my properties as some are young families.

There seem to be a few solar switch solutions Rob if you Google. Failing that just set the immersion timers to operate each side of midday. This is our regime, it comes on for 40 minutes around that time just to ward off Legionnaires' disease since heat pump can struggle to reach the higher temps especially in winter.

Rob we have an Immersun unit to transfer the power. We don't heat water other than with solar from May through October even when we have guests. We have a 3.9 kW array & from Nov a 4.2kWh battery system.

We use 3kW per day May through Oct so could be off grid for electricity 1/2 the year. The battery payback at 35p / kWh is 6 1/2 years . The batteries cost £3.1k but will have taken 13 months to arrive due to supply issues.

Rob look at an iBoost, it's a solar diverter that can feed any excess solar to the immersion heater in the hot water tank, probably about the cheapest option.

Thanks for sharing that Richard, very interesting and profitable.

Iboost looks just the job, email and installation enquiry sent. Thank you

The Myenergy Eddi system is probably the best on the market as can feed 2 x resistive loads but main benefit is that it has its own in built programmable boost timer, so even if you have low PV output due to weather conditions (Autumn/winter), it will still turn on the hot water immersion at your pre determined times. The more simple iboost and Solic etc do not have a programmable timer.
The Eddi unit also has an LED screen showing the the amount of power being exported to or imported from the grid and has web connectivity.
UK built.
Very good customer services.
They also do a nice range of EV chargers.

Setting immersion timers isn't a great solution although easy, as you could be exporting nothing to the grid (all PV being consumed) but then your turning on a 3kw immersion during peak times.

BTW - All the immersion controllers work by varying the voltage to the resistive load - i.e immersion element. They do not just switch on the load (as the very first controllers did) as this would be pointless unless your generating more than 4 kWp which many standard domestic systems will never achieve.
The immersion controllers monitor the energy being exported to the grid and once above a pre set level of say 200w, they then switch on at a low voltage the immersion. More power being exported = higher voltage. This is why an immersion controller is a huge benefit as even in winter the PV may export and so that energy can be fed into the hot water cylinder, maybe only a little but it still helps raise the temperature in the cylinder.

On Monday we finally got the solar batteries installed. The kit consist of an AC to DC & vice versa inverter plus two li Iron batteries giving 2.4 kWh each so 4.8 kWh as installed with 4.2kWh being useable. If we modified the PV array inverter we would lose our Feed In Tarriff which is roughly £350 pa & remember we get that automatically even if we consume all we generate. If you don't have a FIT one common inverter for the array & batteries might be more sensible.

This November to before the install we bought & used 6.8 kWh / day and last November with poorer weather 8.9 kWh. The difference might also be that in 2021 my MIL would spend the weekend in our conservatory watching the birds in the garden & we heat that electrically underfloor. Now she is basically bed ridden so not coming at weekends.

Tues we generated 6.5kWh. We consumed 8.66 kWh. The batteries stored & delivered 5 kWh & the pv array 1.5kWh so we bought in 2.16 kWh.

Wed despite very poor weather till noon we generated 4.8kWh, we consumed 6.6kWh (the difference was no laundry was done on Wed). The pv array supplied 1.8kWh and the batteries 3 kWh. We bought in 1.8 kWh.

The cost was £3.3k but I undertand that has increased as ours took 14 mnoths to deliver from order due to COVID etc.
Payback I'm expecting to be under 5 years. Based on 2 days it is already looking promising.

So not off grid but in May to Oct we buy 4kwh/ day so we will be.