I paid about £6000 for my 4 kW system on my house roof in my previous house in 2013.
We also had a solar boost plus box which heated our Hot water tank immersion heater element so effectively providing free hot water in the summer.
It would be interesting to know how much that would cost now?
The odd thing is, I’m pretty sure that we only got something like 12.7p per kilowatt hour FiT for generating electricity when we began, which was index linked to inflation.
But the graph I just found says we should’ve got more than that.
That’s a mystery that probably will never be solved.
Octopus are paying 15p per KwH but you have to buy fron them too.
I agree about the water heating - our diverter runs the immersion heater on surplus solar and so we very rarely fire up the oil boiler except in winter. Our hot water tank basically acts as a battery and so the payback time would be too long if we had actual batteries. It will be different when evs have bidirectional charging. The technology has been around for years and I can’t understand why it isn’t available yet as it would be a game changer in all sorts of ways.
Diverters/immersion heaters seem to be pretty standard these days: I can’t imagine that anyone with PV wouldn’t have one.
What I don’t quite understand is why, if you have a heat pump, the PV power isn’t diverted to that instead if they are several times more efficient that direct electric heating.
You probably did get more than that. The earlier fit payments were pretty good, and dropped over time. Remember though that there were two payments
Payment of X pence per each KW you generate
Payment of Y pence per each KW you export
However because you couldn’t measure export power before Smart 2 meters (mine only came in this year), they assumed you exported half of what you generated.
I was one of the last ones to get FIT in March 2019, and my current payment (which does change - not sure criteria)
Payment of 5.03 pence per each KW you generate
Our heat pump has averaged 1.3kWh/day over the last 121 days. On days when it does not heat the water it uses 0.3kWh. When it heats the water it ranges between 1.7 and 2.3 depending on how cold the tank temperature had dropped. Occasionally I raise the temperature to over 60C with the immersion. Our cylinder is 200l.
Exporting seems much better and is mostly during the peak period.
We have an Emporia monitor on the electric circuits.
We don’t have one and are using a traditional hot water cylinder with a timer switch so that it’s only heating during times with good solar production. The supplier who installed our system wasn’t in favour of them, saying they had removed most of the diverter switches they had installed. I’ve never really understood the benefit of them, as you need to heat the water once you draw from the tank, and once it’s back to the thermostat temperature, it will stay there until you draw again anyway.
I guess it must depend in part on how much solar generation you have, and how much hot water you use. If you can depend on it to provide most of your hot water there wouldn’t be much for a diverter to do.
A heat pump has to work hard to reach 60°C so some are set to lower hot water temperatures, maybe 50°. In this case, a diverter controlled immersion heater can still heat to 60° to maximise use of solar, assuming that it’s more cost effective to use it than to export it.
We currently have a “free hour” of power, so heat the water from 6 to 7am before the morning showers etc, and then have the thermostat on from 10am to 5pm using either solar or import. But we are changing suppliers, and will be on a fixed rate, so may try skipping the morning heating and see if we have enough hot water with only heating during the day. I’ll be in trouble if there isn’t enough hot water for the girls showers!
Hot water cylinders these days tend to be main pressure with a heating coil and a coil to transfer heat to the outgoing water. I can see little point in overheating the water as it will be too hot at the outlets and need to be mixed with cold.
It only needs to be hot periodically to kill off Legionella. Do people then ensure their pipes and shower heads are sterilised!
The recommended shower temperature is a maximum of 38c with a limiter that can be overridden. The main effect of higher temperatures is to open up skin pores. However, advice suggests that this should be reversed for medical reasons. The effect of hot water on hair is also not good. I feel much more invigorated by a cold final stage which is also good for the circulation.
I don’t feel that my hot water system is a breeding ground for Legionella needing to be constantly killed off. The recommendation is weekly or biweekly.
If you think about an immersion will draw 3KW which means unless you watch for clouds, some of that will come from the grid (excluding battery people). The advantage of a solar diverter is that even if you are just over generating by 70Watts, it will divert that 70Watts to your immersion tank automatically. All these small amounts do add up. For us it means free hot water 90% of the year set to 60-70degrees. Our gas bill reduced by more than a third, but that is also helped by rigging up an electric fire to the diverter (when hot water has reached a usable temperature), giving us cheap heat in the winter, often enough not to need to fire up the boiler. I found it a no brainer and estimated I got my money back in 2 years.
I cant see why anyone with batteries would have their solar diverters removed unless they were moving to a heat pump.
In this weather the ASHP will operate with a Coefficient of Performance of more than 5 in much of the early stages reducing gradually to 3-4. It’s a 12kW (output) unit so that 3kW of electric at the end is close to 12kW. This is nothing compared with the 30kW gas boilers whose size is skewed to combi hot water production.
Agreed Solar Diverter for hot water a no brainer . I’ve got a EV and can heat water in morning and charge car in afternoon . Plus with Fit payout my gas and electric energy bills for last year were more than covered. Plus running car all summer for nothing unless going on a long journey.
I’m still not understanding this. Do you have a variable thermostat setting, or are you using hot water for radiator heating? When we draw hot water from a tap, the cylinder will reheat, hence we use a timer so that only occurs during the good daylight hours. If it’s cloudy, we import that power from the grid. How do you ensure you have hot water on a day with very low solar generation?
