The Doctors Blog - Solar tips, tricks and pitfalls

Background - Grid Voltage and Harmonised Standards with Europe
Since electricity supply standards were harmonised with Europe in 1988, it is law that the electricity supply to your house should provide 230 volts give or take, +10% -6%. That's a huge range, from 216.2 and 253 volts. Before the harmonization of standards, the nominal voltage was 220V in Europe and 240V in the UK. Nothing on existing networks has changed though. The Uk grid is still 240V, parts are even operating at 250v due to legacy equipment and this is deemed to be within the acceptable range. This way of creating a common standard allows new equipment and networks to be designed and installed to the new standard, whilst not requiring any expensive changes to power networks across Europe.

Matching supply to equipment
The upshot of this is that although all CE marked electrical equipment is designed to work at UK voltages, it is not necessarily designed to work efficiently or provide an optimum service life. Electronic equipment tends to be manufactured for the European market as a whole and as such is designed for 220V. This is where fitting a voltage optimiser can help. By stepping down the voltage in your building by around 20 volts, your supply and equipment are better matched. No electricity is wasted by equipment that's poorly suited to the supply and the service life of that equipment may be extended.

Electricity Savings?
This all depends on what equipment is in use in a given installation. The savings that can be made typically come from electronic equipment such as computers, fluorescent lighting electronic ballasts, LED lighting, and motors with variable speed drives. These are known as voltage independent loads. For other load types the picture is more complicated. For restive loads such as an electric heater or a kettle that use electricity to heat an element, when we turn down the supply voltage we will also turn down the power output. This will not save electricity, the kettle will just take a little long to boil but the kettle itself may last longer as it's not working quite as hard but it may have a longer life as a result. An office is the perfect place for a VO unit to realise sizable savings. Any industrial setting would need very careful consideration due the impact of lowering voltages as it may effect motorised processess

For the average household?
Research conducted into the VPhase VX1 voltage optimisation unit registered with the energy regulator OFGEM, is large and detailed enough for me to confidently shed some light on the matter. The report found average electricity savings in domestic houses of 5%. HOWEVER, The savings made across the study were found to be very variable, as high as 19% but as low as -4%, (yes, MINUS!) The takehome message here is that voltage optimisation units in domestic installations can save electricity, but it's very hard to give a specific figures because each installation is so different. I could not find anything in the report to explain the instances of high savings rates so can't say confidently who would be likely to see a worthwhile benefit. (click here to view the full report)

The Feed-In Tariff has ended

As of the 1st of April 2019 the feed-in-tariff (FIT) is closed to new applicants. Under this government scheme people were payed a fixed amount for the renewable wind and solar electricity they generate. In-spite of the flaws in it's management, this initiative can be credited with the rapid and wide scale adoption of solar panels across the country. Some have seen remarkable returns for their investment.

If you were to install a new solar photovoltaic system today, sadly you will not be eligible to claim the feed-in-tariff. Payback figures and timescales for solar PV are subsequently very modest, relying entirely on the energy savings made when green electricity offsets use from the grid. Where there is a continuous demand for electricity during daylight hours, and especially if that load is higher in the summer (such as with refrigeration or air conditioning), it is still possible to see a payback in the lifetime of a PV system without the FIT.  The energy saving trust cites that the time it will take for the savings to pay for the installation is 24 years. This is a very long time to wait.

What's on the horizon for Solar PV in the UK?

Enter the new Smart Export Guarantee (SEG)
The SEG is a new government initiative and very different from the FIT. Under the SEG, energy suppliers from Npower to British Gas, will be made to offer tariffs with a guaranteed price for the electricity that you export to the grid. Unlike the FIT, you will not get paid for all the electricity you generate. However, the surplus solar you can't make use of can be sold back to the grid. How much exactly will be determined by the market and will depend on how much energy providers want to pay. Octopus energy is one supplier that's ahead of the pack in offering innovative energy packages, perhaps most notably perhaps for cheap rates for charging electric vehicles. For those with a suitable smart meter, this is needed to reliably measure export, Octopus are offering deal with a guaranteed export rate of 5.5p per KW/h. Figures from the Energy saving trust suggest a minimum payback term of 17 years at this rate assuming you're at home all day. If you're not home much then the payback time could be considerably longer. This is a big improvement on the 24 year payback on electricity savings alone, but it's difficult to imagine that it will have much impact on the rates of new installations.

For now and the foreseeable future, the principal reason for installing solar panels  on your home is environmental and not financial. In the meantime, I'll be keeping everything crossed that this upcoming election will bring more substantive and inclusive renewable energy initiatives to fill the hole left by the feed-in-tariff.

Here's a link to the Energy Saving Trust for more detailed information on the subject.

It has come to our attention that a number of domestic solar owners have been approached by pushy companies using hard sales tactics, such as offering "free health checks" to get through your door, and once inside pushing them to have unnecessary and sometimes expensive work carried out. One such example is the installation of high quality solar inverters from the SolarEdge. The design of this system incurs additional labour costs over a conventional string inverter replacement as panels on the roof  need to be lifted to install “power optimizers” behind each panel. It is in my view a top notch bit of kit with several benefits and worth the extra effort in several scenarios. Increased yields from SolarEdge systems are real, but usually only marginal over a well sited and designed string inverter system. If anybody promises vaguely couched promises of "upto 25% more solar yield" then you'd be right to raise a suspicious eyebrow.
If you have encountered pushy "sign up today" sales tactics, backed up by impressively high performance promises, please proceed with caution. If you want a second opinion we are here to help.