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Hi all,

New to this forum so apologies if this topic has been done before.

I have moved into a house last year in September 2021. About 1 month later, our energy supplier went bust (Pure PLanet) and we were shifted to Shell energy. Since moving in, I replaced 106 halogen downlighters and shifted everything to LEDs. I removed a working boiler to fit a Stiebel Eltron WPL 25 Air source heat pump and just this month installed a 5.6kw solar system with a solar edge inverter. I am awaiting delivery of a battery bank (10 kwh) from soalr edge although I am open to changing that. I have no EV...yet.

The question I have for the group is how do I balance out the heat pump in terms of timing with the solar supply. at the moment, I find myself expeorting nearly 50% of production. the heat pump works best is my understanding when it is running all the time although I do feel that a break in the night would make more sense.

ANy ideas?

106 halogen downlighters !, wow, I recall moving into my house with 8 x 100w kitchen spotlights and could not believe it.

You proposed battery bank will greatly help reduce your export but your heatpump will generally run in times of the year with very little solar apart from the spring.

But if running your heatpump on your battery bank. it will be drained in little time, even I, with my large battery bank would typically run out of battery if I did not maximise everything including the heatpump overnight on cheap rate.

Until recently you could have Octopus Go at 5p / kWh for 4 hours and you did not need a battery. Now its 7.5p / kWh and you need an EV, although I have heard you just tick a box online saying you have one when you apply with no further evidence (for now). You also need a smart meter if you have not already got one.

Solar produces a huge amount of electricity in summer when your heat pump is switched off. A heat pump consumes a huge amount of electricity in winter when your solar produces little. The truth is that you solar and your heat pump have little effect on one another.

The battery will reduce how much electricity you export in summer but won’t do anything in winter unless you have a ToU tariff such as Octopus Go.

Are you on a dual rate type electricity supply like E7? What does your HP supply CH & DHW or just CH? Does the HP supply the CH directly or via a Buffer tank/Thermal Store? Is you HP "Smart Grid Ready" ?

You do not mention a PV diverter such as an Eddi. which my be a simple way of utilising more of your PV in the short term.

Just for reference/comparison:

We have a Ecodan ASHP, 3.3KWp PV, Eddi and a 430L Thermal Store (TS) coupled to UFH in 70mm S&C screed, 225m2 Dormer bungalow all electric in Yorkshire dales. The TS has connections for ASHP, Solar Thermal, WBS and is fitted with 3 immersion heater 2 of which are controlled via the Eddi.

In winter the PV production is so low it basically contributes nothing. In summer the ASHP is normaly turned off (this year it has been off since the start of May). In winter the ASHP heats the TA which in turns runs the UFH. We usually run the ASHP overnight (E7) that both charges the TSand the UFH screed which acts like a large storage heater (22 tonnes of screed was used). We find that unless the weather is exeptionally cold the ASHP rarely runs during the day. During spring/autumn the ASHP runs at night, but I am looking at running it when there is surplus PV - not yet done. The Ecodan is supposed to be Smart Grid ready and am hoping to control that via the Eddi - though it appears there may be significant limitations.

Countrypaul wrote: ↑Tue May 17, 2022 9:42 am
In winter the PV production is so low it basically contributes nothing. In summer the ASHP is normaly turned off (this year it has been off since the start of May). In winter the ASHP heats the TA which in turns runs the UFH. We usually run the ASHP overnight (E7) that both charges the TSand the UFH screed which acts like a large storage heater (22 tonnes of screed was used). We find that unless the weather is exeptionally cold the ASHP rarely runs during the day. During spring/autumn the ASHP runs at night, but I am looking at running it when there is surplus PV - not yet done. The Ecodan is supposed to be Smart Grid ready and am hoping to control that via the Eddi - though it appears there may be significant limitations.

How well would the winter output from a share in Ripple balance the need for heat via the HP? I know we will always have to pay the grid costs etc on what we get from our turbines, but could it be that the Ripple returns net of grid fees would offset the power you need to buy mid-winter?
A

a lot to think about.

i am quite new to all this so forgive me if I do not follow all the abbreviations.

I know the Stiebel has a solar diverter, so in a way, I have a hot water battery, but at the moment, I am not sure it is doing much so have contacted the installer to make sure it is well configured.

I am thinking of going to Octopus and using their rate where there is the 4 -5 hour window of low power cost. I would either use that to top up the battery in winter or maybe go for hot water via the heat pump.

The heat pump does 2 circuits dhw and VD heating (not sure what CH is). It does appear very efficient with the output being a cop of >5 consistently so far.

Am waiting on the batteries, solar edge ones as they will apparently also be instituting home battery backup via a firmware update soon. and will proceed with the octopus supply, vs shell.

CH - Central Heating

The only hope with any kind of electric powered heating in the winter is with Time Of Use tariffs like Octopus Go. No amount of Solar Panels will do anything. Just set the thermostats to 30 degrees at night and then back down when the tariffs stop. You want your electric bills to look like mine at 7p per Kwh. I draw in exess of 12kw for 4 hours every night.

I agree with countrypual.

We have 30KW of PV, 63KW battery bank, but never enough power in Winter.

Ok, will definitely do the switch. I am surprised PV generates so little in winter. I was expecting a little background at least. As long as the heat pump is able to maintain a cop of 4 or more, it is still better than my gas boiler. The house is well insulated and has underfloor heating on 2 floors and all teh radiators have been supersized so will see if it remains efficient.

SO as a summary, best approach is in summer/spring, charge up batteries with solar and use in evenings and in winter charge the batteries at night, then optimise the heating as well and hope the house keeps it all in.