Going Solar / Off the grid

RoadToRiches

Considering my options for going solar powered. Seems like there are a lot of rogue traders out there advertising and now have no clue who to go with.

Does anyone have any good recommendations. I'm using around 10,000kwh on gas and 4,500kwh on electric.  I'd like something to be able to cover this if at all possible.  I have room on my roof for 18 panels, and would want a back up battery as ideally would not want to feed it back into the grid unless absolutely necessary as they pay a pittance compared to what they charge for electric.

I don't yet have a heat pump, this is next on the list with radiator upgrades / under floor heating retro fitted.  It's a newish build, 2014 so should be quite energy efficient already - its EPC is a B grade.

Advice on how to avoid the sharks and what a good system should cost? I hear I should get 5k back for installing heat pump and I could get back up to 3-5 times the amount of electric put in. 

[Deleted User]

Off Grid, not a hope, sadly. I have a 6.5kWp array and a battery. Last December, my worst day for generation was just 350Wh. My best day was just 10.5kWh: not enough, to power a home and run a heat pump on a cold Winter’s day. Total monthly output was 108kWh. The ‘good news’ is that we are effectively off Grid from late March until October: when the heating is shut off.

Have a look a look at YouGen for installer recommendations. I would chose a local installer if you can as they tend to have a working relationship with your DNO. Bear in mind, that if your local Grid infrastructure is poor you may end up with a low export limit. Also be prepared for your DNO to insist on a 3 phase supply - particularly, if you have a heat pump in mind.

PS. For some unfathomable reason, solar prices seem to have increased since last year! The cut in VAT will help.

gefnew

Try reading this thread and add your quotes and other questions here.
Green & Ethical MoneySaving — MoneySavingExpert Forum

RoadToRiches

gefnew said:

Try reading this thread and add your quotes and other questions here.
Green & Ethical MoneySaving — MoneySavingExpert Forum

Thanks - can a MOD move this to here if they see this please.

QrizB

RoadToRiches said:

Does anyone have any good recommendations. I'm using around 10,000kwh on gas and 4,500kwh on electric.  I'd like something to be able to cover this if at all possible.

Let's assume you can reduce your heating energy demand to 3500kWh/yr by using a heat pump, so a total electrical demand of 8000kWh.yr.

As Dolor has said, covering 8000kWh/yr with solar, for 12 months of the year, would require a combination of a huge array and a huge battery.

Let's use my array as an example. During December last year I generated 41kWh from 2.72kWp of panels. It looked like this:

Imagine you actually wanted 1000kWh of electricity (for heat and power) during December. You would need an array almost 25x larger than mine; a 66kWp array. That's not something that will fit on any reasonable roof; with current panel efficiencies you're looking at 330 sq. m. of panel. It's a small solar farm, roughly £70k-worth.

Plus you'll need a battery big enough to store the power from the first ten days of the month (when it was generated) until you need it in the next twenty-one days. That's around a 600kWh (0.6MWh) battery, another £200k-worth.

So that's a total of £270k spent to avoid the cost of £150/yr for the electricity standing charge.

But of course, in the summer your array will generate far more electricity than you can possibly use. In July, for example, you'll generate maybe 7500kWh and only use 500kWh of it. Those 7000kWh from July alone are worth about £350 - more than twice the annual standing charge - but without a grid connection you won't be able to sell them to anyone. Over the whole year you'll have about 58000kWh spare, worth at least £2900, that you'll waste.

Let's try a different approach. Rather than going off-grid, stay grid-tied but choose a system that will match your 8000kWh/yr consumption. That's a system of around 8kWp, maybe £9k to install. Add a battery if you want; a 10kWh system would cost around £4k, so a total of £13k. You'll be effectively off-grid from March to October, will be able to sell your surplus electricity and can cover the cold, dark months with commercial electricity bought in from the grid.

matelodave

The big problem with trying to go off-grid with solar and a heat pump is that you don't get anywhere near enough energy in the winter to run a heat pump and a lot more than you need in the summer when you don't heat the house

We use around 8000kwh a year but around 5000kwh gest used in five months between November and March when the sun doesn't shine very much and 3000kwh in the remaining part of the year when it does. You only need a few days of snow covered panels or heavy cloud and you'll not get enough to even keep your lights on let alone heat or cook.

Months like December, Jan and Feb can get through 1200-1400kwh each and some days it can peak to 50-60kwh when its everso cold and damp.