Who pays for new home solar generated power ie Feed In Tariff

After installing the PV you can then buy lots of gadgets to use electricity  generated rather than exporting it.

Last week I had a conversation with a husband and wife in which I asked if the bathroom underfloor heating had run off the PV before the bathroom installer hacked it out to make a wet room, because it had a cable running to an ImmerSum unit in the loft next to the hot water cylinder. 

When they bought the bungalow the gas supply had been disconnected then the PV installed along with an air source heat pump and other “gadgets” to use the generated electricity. All retrofitted into a 1970's without sufficient insulation. 

The air source heat pump received a four letter review rather than a four star review and the rest of it did not fare any better with a number of expletives being used to describe them and the system. 

First and foremost the rental property needs good insulation, draught proofing and controlled ventilation, then go from there avoiding the snake oil salesmen. 

You can get about 5p per unit exported from most suppliers. A good option if you have solar for personal use is a solar diverter such as Eddi. This will divert surplus generation for up to two devices with resistive heating elements such as immersion heater elements or storage heater. Saves cost of importing at normal unit rate and avoids having separate solar thermal heating which just adds extra complexity to your renewable energy system. There is also the Zappi EV charger that can divert surplus generation to charge vehicles. I've no connection to the company but do have Eddi and it's providing all our hot water just from surplus on our small 2.6kWp system in the north of Scotland.

Cheers Andy

I can see the point of “diverting” solar power to heat water if the normal method is gas, but how does it help otherwise?

You divert power that only earns you 5p per unit to heat the your water ( or heating) that you will otherwise have to import at ~19p per unit from the grid. If you do not have gas (we don't) it's a good solution during summer. The wood stove provide more than enough hot water during winter! The diverter maximises your generation benefit as it only diverts excess power. If you have only a small system you may only divert 100W - 500W but over the day this accumulates. In fact it keeps the immersion tank topped up with hot water constantly during the day. Total diversion might be equivalent to 3kW for one hour continuously. Certainly enough to heat a tank. When the immersion thermostat operates the diverter will then divert the excess to the lower priority load. Same principle applies to the Zappi EV charger. Car gets charged via your excess solar instead of using grid. Not much use if your working away from home so a better option is one of the taffifs that have very low rate between 00:00 and 04:00.

I don't quite see what is being diverted. You have simply chosen to generate your own electricity rather than purchase it from the national network. The question really is how much does your home-generated leccy cost?

I'm probably not explaining it too clearly Chris. Previous to having the diverter if we wanted hot water in summer we would use the 3kW immersion heater instead of firing up the wood stove. Even if we switched the immersion heater on when the solar system was generating peak power at about 2kW, with base load of about 500W we still had to import 1.5kW to heat the water. Very rarely will we be generating that power and more likely about 1-1.5 so water heating required about 2kW imported. That also assumed we remember to switch the immersion on when the sun is shining. Now we just let Eddi divert the excess to the immersion during the day so the water heats gradually with whatever the surplus is above our baseload. Eddi takes care of the switching automatically and has very fast response times. If we boil the kettle for tea there's obviously no excess but as soon as the kettle switches off the Eddi switches excess power to the immersion heater. The result is we have hot water without cost of importing from the grid. We maximise our own use of our generating capacity and minimise our import of grid power. Cost saving may be minimal in the short term but the convenience of hot water during summer at zero cost is a real benefit. Not sure if that helps explain the benefit of the diverter but it's worth visiting the MyEnergi web site for a technical explanation of the UK manufactured products. Cheers Andy

With regard to what my self generated leccy costs I admit I'm one of the very lucky ones to have a system installed 10 years ago when FIT payments were ridiculously generous. The local Black Isle Agricultural Show had the local company Barres advertising an offer that seemed too good to be true. The system was more expensive that can be bought now and that was the point behind FIT payments to kick start the industry. We have had sufficient payments within 8 years to cover the £8600 capital cost. In that period we also saved at least half of our electricity use and were also paid a small amout for 50% of the total generation of about 2000kWh per annum from a 2.6kWp system. Effectively we now earn money from generating due to FIT payments which no longer exist for new installations. New installations probably have a similar payback period of 10 years but given that 25 years minimum life to 80% of original capacity the longer term investment is better than a building society. We happen to be fortunate having a south facing roof in the sunny north of Scotland so get over 2000kWh from our small 2.6kWp system. Mind you with a single string system every bit of snow needs to be cleared off every panel in winter to avoid importing power from the grid!?.

A neighbour appears to have recently installed PV and air con as they have panels on their roof and an air con unit on a gable wall.

Sparkingchip: 
 

After installing the PV you can then buy lots of gadgets to use electricity  generated rather than exporting it.

 

Last week I had a conversation with a husband and wife in which I asked if the bathroom underfloor heating had run off the PV before the bathroom installer hacked it out to make a wet room, because it had a cable running to an ImmerSum unit in the loft next to the hot water cylinder. 

When they bought the bungalow the gas supply had been disconnected then the PV installed along with an air source heat pump and other “gadgets” to use the generated electricity. All retrofitted into a 1970's without sufficient insulation. 

The air source heat pump received a four letter review rather than a four star review and the rest of it did not fare any better with a number of expletives being used to describe them and the system. 

First and foremost the rental property needs good insulation, draught proofing and controlled ventilation, then go from there avoiding the snake oil salesmen. 

Totally agree that insulation and draught proofing is the number 1 priority. I'm insulating our suspended timber floor as 1/5th of heat loss is via uninsulated suspended timber floor. Managed to install a third of it during winter months and immediately noticed the difference when bare foot in bathroom and kitchen. Should have done it years ago.

Where is DZ when you need him most? ?

So your panels generate 2 kW of which 0.5 kW powers computers, vacuum cleaners, fridges, etc. - the “base load”. That leaves 1.5 kW to heat the water. I imagine that you could put the immersion heater across that supply and you will get some useful heating, but the voltage will drop. That's fine if everything will run on 150 V or thereabouts, but I suspect that the electronics will avoid a voltage drop so you import (i.e. purchase) 1.5 kW. You as opposed to the National Grid are only providing 50% of your energy.

When the thermostat is satisfied, you can export your surplus, which is great, but only because you were an early adopter and get a good rate for the energy.

So actually what is happening is that when the immersion is on, you import; and when it is off, you export.

Conservation of energy and Ohm's law!