Buying house with Solar, advice needed

[Kuro507]

Morning All

 

I have just had an offer accepted on an old stone house which has Solar (PV) on the roof. I am trying to get my head around how it works and what I could do to minimse my electricity costs to make it as efficient to heat etc as possible.

 

What I know so far:-

3.84 kWh of panels, largely south facing. Solis Inverter in the loft. 

Installed May 2015 with Feed in Tariff of 14p/kWh. (For 20yrs)

Generates around £800 per annum FIT (Based on last 2 years).

Solar iBoost box in airing cupboard, I believe wired to 2.3/3kW immersion heater in hot water tank.

Digital generation meter next to electricity fuse boards.

Heating is via oil filled radiators in all the rooms (3 bedroom over 2 floors). Rointe K series units

Hot water is via immersion tank and also a Redring instant water heater.

 

With the big thick stone walls, I am limited as to home much additional insulation I can install without making the rooms small.

I will review how much there is in the roof and increase it.

 

Whats the most efficient way to heat the house and water and make use of the FIT?

Its all new to me, so any advice, gratefully accepted. 

[ProDave]

No 1, make sure on completion the FIT is transferred to your name, make that a condition of the contract.  you then submit a quarterly generation meter reading and receive a quarterly payment for that.

 

Easiest way to self use most of what you generate is to use all the big appliances like washing machine, tumble dryer, dishwasher etc close to the middle of the day, one at a time.  the solar iboost just works on it's own to send any surplus to the hot water tank, so best to arrange the hot water heating to not heat the tank in the morning so there is plenty of capacity to dump heat into the HW tank.

 

If you are heating just by electric heaters, then run those in the day as much as possible, though with little insulation you won't be able to avoid using them in the evenings.

 

a new heating system would be my No 1 priority. Gas, Oil etc or if you can make the figures work, an Air Source Heat Pump, but you need a pretty good idea of the heat loss from the house to work out if that will work.  e.g my little 5kW ASHP heats our well insulated house nicely but would barely scratch the surface of the heat needed in an old stone house.

[SteamyTea]

What @ProDavesays.

 

Basically you want to dump the power into appliances.

Then use Economy 7 as your back up option for winter.

[Kuro507]

Thanks for your comments.

 

I don't believe economy 7 is there at the moment.

 

There is a tiny little courtyard garden with no external access, no option for Gas or Oil. Not unless it was the portable cylinders which could come through the house.

Whats the argument between hot water cylinder heated with immersion vs instant water heaters at each tap?

 

I assume the FIT is based on what you add back to the grid? (Total generated - whats used = excess back to grid)

 

I will certainly see what can be done to further insulate the roof, but the walls are at least 18" thick, so effectively a large thermal mass to heat up.

 

If you have a tank of hot water, can that not be used for some radiators as well?

 

I forgot to mention there is a small enclosed log burner upstairs, so that will generate some welcome heat in winter months. I may well work out a way to duct some heated air  downstairs from near that.

 

 

Edited September 29, 2020 by Kuro507

[Roys]

FIT payment is paid on the total generated, each quarter you submit your meter reading which then gives you the total generated for the month. They then work out your total payment using a 2 part sum, say you generated 300 units for the month then depending on the contract the sum might br something like:

300 x 12 p = £36 

plus a presumed export back to the grid payment usually an additional 50% so £18

gives you a total payment of £54

The presumed payment for export is just that, presumed, so it doesn’t matter payment wise if you use it or not, that is why solar diverter became popular as it uses up the the surplus electricity diverting it to water heaters or similar.

 

[Kuro507]

Thanks Roys

 

So definitely a reason to avoid a smart meter if you can use more than 50% of what you generate?

 

Are there any other costs effective forms of energy storage to consider?

 

I seem to recall reading a blog a few years ago where somebody had a more modern heat store, some sort of thermal brick or something.

 

 

[SteamyTea]

3 minutes ago, Kuro507 said:

I seem to recall reading a blog a few years ago where somebody had a more modern heat store, some sort of thermal brick or something.

A thermal store is an insulated box with something in it to adsorb the energy, then a hole to let it out again in a controlled manner.

[Roys]

1 hour ago, Kuro507 said:

Thanks Roys

 

So definitely a reason to avoid a smart meter if you can use more than 50% of what you generate?

 

 

As far as I am aware Smart meters are not set up to detect how much is or is not exported, so as it stands just now it wouldn’t make much difference, however personally speaking I would avoid Smart meters for a different reason.

My reasoning to avoid Smart meters is that it enables variable tariffs to be implemented in the future, so what the electric provider could do is say charge you 10p a unit during sleeping hours but say at dinner time charge you £1 a unit so as to discourage usage at certain times of day because of possible lack of generation capacity. Only my theory so don’t quote me on that?

Anyway in the grand scheme of things there is no advantage to you getting a Smart meter.

[Kuro507]

In summary:

FIT is paid based on 50% of generation, I need to work to use or store 100% of generation to maximize the Solar PV benefit.

I need to look at insulation options to keep requirement for heat generation down.

 

 

Would there be a sensible approach to have a larger hot water tank with a 2nd coil for a couple of radiators in the most used rooms?

We like our bedrooms cool, but living spaces a more normal temperature. 

[Roundtuit]

2nd generation smart meters can measure export,  hence the Smart Export Guarantee scheme that replaced FiT for new installs.  Existing Fit's can switch over to the SEG I believe, but you'd have to fully understand your usage and do the sums carefully to make sure you weren't out of pocket.

[Roys]

1 hour ago, Kuro507 said:

In summary:

FIT is paid based on 50% of generation, I need to work to use or store 100% of generation to maximize the Solar PV benefit.

I need to look at insulation options to keep requirement for heat generation down.

 

 

Would there be a sensible approach to have a larger hot water tank with a 2nd coil for a couple of radiators in the most used rooms?

We like our bedrooms cool, but living spaces a more normal temperature. 

Not quite 

You are get a payment for 100% of your generation

Plus a different rate of payment for 50% of your generation 

The exact monetary amounts depend on your FIT contract 

[SteamyTea]

If you know when the system was fitted, it will be possible to work out what scheme it is on and what the payments are.

[Ferdinand]

1 hour ago, SteamyTea said:

If you know when the system was fitted, it will be possible to work out what scheme it is on and what the payments are.

 

Should this be on the docs from the Land Registry?

 

(I don’t know]

[SteamyTea]

5 hours ago, Ferdinand said:

I don’t know

I don't now either, but there may well be a price on the electricity bill, or a date on the consumer unit.

[Roundtuit]

My guess is installed May 2015, with a Feed in Tariff of 14p/kWh  ?

[SteamyTea]

https://www.ofgem.gov.uk/environmental-programmes/fit/fit-tariff-rates