Are Solar Diverters REALLY Worth It?

a solar diverter allows you to use excess generation instead of exporting it but these units are expensive to buy and install so the question is are they actually worth it let's find out [Music] hi I'm Gary and welcome back to my channel if you already have a solar installation you'll find out there are times of the day when you're generating far more electricity than you can actually use and as we saw in one of my previous videos having a battery is a great way to store that excess for use later in the day another way to make use of that excess is to heat up your water instead of using your gas boiler and to do that you'll need what is called a solar diverter this is an electronic device that monitors how much excess solar generation your installation is producing throughout the day and diverts that excess to heating up your water cylinder there are a number of Brands available in the market today here are three of the more popular ones solar eye boost on the left my energy Eddie in the middle and solar Edge Smart Energy on the right before we assess whether these diverters are worth the money or not let's first understand how they work to make use of a solar diverter to heat your water you'll need to have a water cylinder in your house like this which typically can hold anywhere between 150 and 500 liters of water let's take a look inside to see how it works there's a cold water feed in at the bottom which keeps the cylinder full of water then to heat that water there's a hot water feed going into the cylinder coming from your gas boiler which transfers its own heat into the water inside the cylinder until it reaches the desired temperature hot water can then be drawn out of the top of the boiler at any time which is replenished by more cold water coming in at the bottom because heat rises the cold water coming into the cylinder at the bottom will not reduce the heat of the hot water near the top too much now the feature of the water cylinder we're interested in is the immersion heater which is an additional water heater but this time powered by Mains electricity it is normally switched off but can be switched on as a backup facility should the gas boiler ever fail and it represents an ideal mechanism that a solar diverter can use to heat the water with any excess solar generation let's look now at how your solar diverter would integrate with your solar installation here is the AC Supply coming into the house from the grid that feeds all of the household appliances and here is your solar array and inverter that complements that grid Supply you may also have a battery connected let's assume for a moment that it's an AC coupled battery which connects directly into the AC Supply check out my previous video which looks at the differences between AC and DC coupled batteries the immersion heater of your water cylinder also connects into the AC Supply like so the solar diverter simply connects in between the power switch and the immersion heater turning the power switch on will start the inverter but it won't do anything yet until it has information about what's actually happening in the system it typically gets that information from two strategically placed CT clamps one at the output of the inverter and another next to the meter let's say the house is consuming one kilowatt currently and the solar array is generating four kilowatts the diverter can see there is an excess of 3kw thoughts that would otherwise be exported and so diverts the excess electricity into the immersion heater of the water cylinder this brings the total house consumption up to four kilowatts which exactly matches the solar generation now should the solar generation fall back to say two kilowatts the solar diverter will detect this and drop the power going into the immersion heater accordingly in this case back to one kilowatt as you can see the resulting house consumption drops to 2 kilowatts again exactly matching the solar generation this is a key feature of a diverter in that it can vary its power output to whatever level is needed giving precise control over how excess solar generation is used now you may have a DC coupled battery instead of an AC one this makes it a little more difficult but not impossible for the solar diverter to determine the level of solar generation because the battery is effectively hidden behind the inverter if not configured correctly the diverter can unintentionally drain the battery to avoid this the settings of the diverter can be adjusted slightly so that it looks for a grid export greater than say 100 Watts before it takes any action okay hopefully now you've got a good understanding of how our solar diverter Works let's get into the big question now are they really worth it and to do that we'll need to get into the costs just before we do that these videos take hundreds of hours to produce and so if you'd like to support me there's an easy way you can do that if you're in the UK and thinking of moving your energy Supply over to octopus energy when you call them just give them my referral code and we'll both get 50 pounds credited to our accounts so the first thing we're going to do is to work out how many liters of hot water you require in your household every year then assuming you have a gas boiler what the cost is in gas to heat that amount of water then we'll compare the cost of heating that water with gas to using solar energy instead let's look at each of these in a bit more detail to assess your hot water consumption I looked at the UK Hot Water Association website for some statistics a bath is typically 100 liters of water but only 60 liters of that water comes from the cylinder the rest is cold water and a shower typically uses 18 liters of water a minute of which 11 liters a minute comes from the hot water cylinder the UK Hot Water Association estimates a medium hot water requirement per person per day is between 30 to 50 liters I put a link to their website in the video description if you want to take a look at this in more detail to work out the cost of gas required to heat that water we must first work out the energy required then we can work out just how much gas is actually required to provide that amount of energy this is because gas boilers are not 100 efficient then we can work out the cost of heating that water with solar energy instead now you might be thinking that cost is zero right because we're getting that energy from the Sun but you have to factor in a few things the cost of the solar diverter equipment required and its installation and not every day will be sunny so there is a cost of heating water with gas or grid electricity on days when there is insufficient solar generation and finally the revenue lost by using solar excess to heat water instead of Simply exporting it okay you can see the calculations are maybe a little more involved than you first considered but to make things easier I've been working on a utility with my friend Ewan and I'd like to show you that now so in this utility we're essentially entering a number of details and at the end we'll get an estimation of the payback period so we start with the water requirement and here you can see we have four family members averaging 50 liters of hot water per day and this amounts to 73 000 liters over the year you can change these values to suit your own situation for example if we change this value to 70 you can see the total hot water requirement goes up next is the energy requirement now depending on where you are in the world your cold water temperature will be different and that temperature will also vary during the year so just enter the minimum and maximum temperatures of your cold water throughout the year and we'll take an average next is the hot water temperature required and this is normally a setting on the water cylinder itself from those inputs we have an average temperature difference between hot and cold water and we can use this to calculate the energy first we calculate the energy required to heat one liter of water by that amount and then the energy required to heat a Year's worth of water now we can move on to the gas requirement as we discussed earlier gas boilers are not 100 efficient which means we'll require more kilowatt hours of gas to meet the energy required to heat a Year's worth of water if your gas boiler was a hundred percent efficient you can see that the values are the same and if your gas boiler is only 50 efficient you can see that you need twice the amount of Gas Energy we then enter the cost of gas per kilowatt and from that we can calculate the total cost of the gas which is essentially the total cost per year not using a solar diverter next we move on to the electricity requirement so here is your investment the cost of the solar diverter itself and the cost of installation this gives us our total investment now the sun will not be able to generate sufficient solar generation for your diverter every day so we need to enter a value for the number of days that will happen and from that we can see how many days there will be sufficient solar generation and where there is insufficient generation we can calculate the cost of gas per day to cover that and consequently the cost of gas per year to cover all of those days the next field is the cost of electricity per kilowatt hour this can either be your standard rate or an off-peak rate we then perform the same calculation but this time with that electricity so here you can choose whether we're using gas or electricity to cover those days where there is insufficient solar here we can see the amount of solar generation electricity is required each day to heat your water and this represents the total amount of electricity over the year not exported as a result we can enter the price that we receive for every kilowatt hour of exported electricity and from that we can see the amount of lost revenue and this is important because it adds to the cost per year of using a solar diverter finally with all of the values above we can see the estimation on our payback in this case three years and we can also see the annual savings that we can expect to receive once our investment has been paid back okay so that's the utility let's have a play with some of the values then for example if there are only two people in your family you can see this increases your payback period to six years if you are the only person in the household your payback estimation doubles to 12 years if you have five people in your family then you can see the payback estimation comes down to just under two and a half years now we've used eighty percent for the boiler efficiency but if you have a very old gas boiler the efficiency may be as low as 60 percent this has the effect of reducing your payback period and if you have a very efficient gas boiler you can see that this increases the payback period we can also choose to use electricity to heat our water during insufficient solar generation days instead of gas and depending on the amount you pay for that electricity especially during off-peak this can reduce your payback estimation now what's really interesting is if the amount you get paid for exporting electricity increases this has a drastic effect on your payback period for example with octopus energy in the UK they have just raised their export rates to 15 Pence and you can see the effect of this immediately you will never achieve a payback of your investment you are far better exporting that electricity even if the rate is 10 pence you can see the payback estimation is decades I've put a link to the utility in the video description but you can access it straight away here just open up the camera on your phone and point it at this QR code on the screen so back to our original question then our solar diverter is actually worth it generally speaking for most homes especially where there are three or more people I would argue yes solar diverters are indeed worth it but as you saw in the utility it really depends on your own situation if you can achieve a good export rate for your solar excess you may never see a return on your investment but you know even if the numbers don't show a payback in a reasonable time frame having a shower or a bath knowing that you're paying next to nothing to heat that water and because you're not using gas you're avoiding burning two to three megawatt hours of fossil fuels every year well it just makes that shower or bath much more enjoyable thanks for watching this video hopefully you found it useful please don't forget to like And subscribe and thanks very much for all your support [Music] thank you

Channel: Gary Does Solar

Views: 68,645

Keywords: solar diverter myenergi eddi

Id: 1yAwgye-NVQ

Length: 13min 6sec (786 seconds)

Published: Sat Sep 24 2022