Bramco

Another interesting take on this is the date from the Electrification of Heat trial. The data has recently been published and Trystan Lea from the Open Energy Monitor crew who run the on-line HP comparison site has input the data into a parallel database so that the results can be analysed. Doesn't make good reading as the CoPs are very low, mainly down to poor installations and oversized systems - but I'll bet that the headline of 'poor CoPs' ends up being what drives any future legislation. More detail at -> https://community.openenergymonitor.org/t/electrification-of-heat-trial-data/27445 And the on-line data from running systems is at -> https://heatpumpmonitor.org/ some systems were also on the trial - the installed HPs on here do considerably better as, in the main, they have been adjusted to run well.

OK @SteamyTea, here's some data for you.... Not sure about the 28% line!! But this shows in general that a low draw in the inverter runs at about 20% loss, while a high draw runs at a much lower loss in the region of 6/7%. Quite low, the last line is still 11%. So given your maniacal focus on parasitic loads, batteries will never be for you!! 😄 Obviously, these need to be taken as a general rule of thumb, I don't think the data from the inverter on the grid is v accurate for example. Also apologies for the shift in the headings - this is as it came across from Excel. First 3 columns are what is what is being generated, next 3 columns are what is being consumed. Total Load less PV Battery Delivered Grid Load Grid Loss %age Battery to house 0 397 397 17 340 323 74 19% Battery to house + ASHP 735 2452 3187 18 2971 2953 234 7% PV to battery and house - low PV 1529 -1139 390 58 374 316 74 19% PV to battery and house -high PV 4237 -3862 375 55 325 270 105 28% PV to diverter with export 4747 -17 4730 -1107 3353 4460 270 6% PV to diverter low PV 932 -21 911 -49 759 808 103 11%

@Marvin We had them do the install and obviously the BUS application - this was in 2023 under the £5k scheme. If I'd known they would supply and then inspect and commission, I think we'd have gone down that route as well. We had a few issues but all in all v pleased (touch wood as it's winter!) with the HP.

Marvin, have you written this up - might be very useful for anyone just embarking on the ASHP/MCS BUS thing. I'm guessing it's not that widely known about.

Our house is similar size 250m2 - MCS insulated slab with UFH, timber frame, triple glazed, v good airtightness, MVHR, warm roof. All electric, it cost us £45/month last year for all electricity imported. That's hot water, heating, everything. But we do have 6.kWp of solar and 15kW of battery storage and we're on Oct Int G0, so try (successfully most of the time) to only use the 7p rate. We had the ASHP installed on the old BUS grant of £5k. It's a Cool Energy unit, similar to this one -> https://coolenergyshop.com/collections/air-source-heat-pumps/products/cool-energy-invertech-high-temp-air-source-heat-pump-ce-ivt9-evi so 9kW. Total cost to us, installed was £250 but we already had the cylinders in place for UFH buffer and DHW tank. We had a heat loss analysis from an M+E engineer and Cool Energy were more than happy to use this for the MCS calculations. Unless it's really cold outside, we only run the ASHP at night on the 7p rate - we don't use it for DHW, only for heating. This works fine and even on really cold days, if the sun shines (we get plenty of solar gain) then we don't need to boost the heating during the day. So 9kWs is fine for a house like ours and I'm guessing yours. Have a look at this deal -> https://coolenergyshop.com/collections/air-source-heat-pumps/products/free-heat-pump-kit-for-self-builds-renovations. You get all the kit for free if you qualify for the BUS grant. I wonder if you completed the heat loss spreadsheet that's on the forum and provided proof of the U values of your wall and windows etc, whether they would accept these in place of doing the heat loss calcs themselves - they're a small outfit, so it might be worth a try.

Interesting read - like lots of us on here, I'm always working out ways to reduce our usage and make the most of off peak electricity prices. Like @Marvin we're all electric, with PV, ASHP and in our case batteries not an EV. Now we're in the new year, I'm just working out what we've used this year. At one point in your analysis @SteamyTea, you say a 20% efficiency loss on batteries would be a best guess. This is one thing I was concerned after I'd installed our batteries. What I've noticed is that at low wattage the losses are higher. If this is the case, then there's probably a base loss due to the inverter being 'on' so to speak and then a %age of the actual wattage being delivered. An example from this morning, with a house load of 323W the inverter was actually drawing 397W from the battery, so 19% - which is about your best guess. Later in the morning with the ASHP drawing power, the house load was 2953W and the inverter was using 3187W from the battery (2452) and PV (735W), so about 7%. Unfortunately for all battery users the lowest loads will be the most common and higher loads more intermittent, so losses would be closer to the 20% than the 7%. I'll have to try to dump data from the inverter to get more data points, for example when the batteries are being charged, either from the grid or from the PV etc.

The open energy monitor guys do a kit -> https://shop.openenergymonitor.com/level-3-heat-pump-monitoring-bundle-emonhp/ And they have a site showing the data from people who have installed the kit and made their data public -> https://heatpumpmonitor.org/

I'd call them and speak to Dave. Hope you get sorted as their support is return to base and test in Grimsby until it fails again !!!!!

And if you don't fancy making something, try open energy monitor - they do a great bit of kit with up to 6 sensors that can be used to monitor the whole house and several appliance circuits as well as up to 6 temperature sensors -> https://openenergymonitor.org/ Their systems are all open source, based in Wales and doesn't rely on any cloud servers if you connect up to a local system. More data than you can shake a stick at as well of plenty of graphing options and apps to waste hours and hours of time on.

In our case, they both were ignorant of the actual legislation - or maybe they were pandering to the 'oooohhh, it's Green Belt, you can't build there!!' mob. But the legislation of course says otherwise for 5 specific cases of application. They should have been cognisant of this and directed the ctte appropriately, as our case, as the appeal proved met one of the criteria.

Solcast can also be useful for getting forecasts as well as I think for historical data -> https://www.solcast.com/ We use it for a dashboard done with the nodered ui tool - borrowed from another source And I know I need to fix it so the sidebar doesn't show.....

We did several times. And on our application spoke for the 3 minutes - which landed on deaf ears. The councillors were completely ignorant of the actual legislation for building in the Green Belt and got it totally wrong, as had planning in their advice to the committee. We took it to appeal and won - the appeal effectively said - 'you're numpties, the application is obviously within the specific clause for the Green Belt of 'infill within a village'. The whole thing was quite stressful. Given the borough has a lot of Green Belt, you would have expected planning in their advice to the ctte and the ctte to know what they are doing.

Agreed - which is why we did one! Unfortunately as we were doing it, a builder with options on a plot of land the village would not have prioritized for new housing found a planning department desperate for quick fixes to their housing shortage. So that was accepted into the Borough LPPt2 as allocated and therefore something we had to accept. A great way of saving land that locals don't think should be allocated, is to designate them as 'local green space' in the neighbourhood plan. This in effect makes planning apply the criteria for Green Belt to any decision. Our plan prioritised a number of small plots which added up to about the same as the large plot the Borough allocated. More than 5 years on, only one of these plots have been built on - a brown field site in the middle of the village - the old British Legion site. The large plot allocated by the Borough has only had some preliminary work done.

My understanding is that a Parish Council's view are treated as if they are a comment by a member of the public. And unless they actually bring up specific planning issues, then they are ignored, as are those from members of the public. Sensible Parish Councils won't object to applications unless there is a valid planning legislation point to be made. But there are a lot of NIMBYS around in Parish Councils.....

Think this was what we did too - if I remember correctly, some inverters have this capability some don't, so you have to choose carefully. The info is on the database, so just download the relevant doc. There are devices that to the limitation separately but ideally you'd have the inverter do it.

At a guess, the spike is maybe what it should be generating and there's a fault somewhere in the wiring which means it only comes through sometimes? I'm assuming the 2 arrays are on separate strings into the inverter? If so, you could try switching the arrays on the inverter - be careful to isolate the DC before you do. This would tell you if there is a fault in the inverter (which would seem unlikely) or in the wiring to the array. Did you do the wiring yourself? If so, it's worth checking each connector to make sure that the connectors are properly clicked into the outside housing. If they aren't, then making a joint can push the connector bit out of the housing causing a fault. EDIT - of course, the spike will be when you came back and slammed the front door in frustration - causing a tremor to run through the house and make the faulty connection work for a bit.

True - and you'd need a helluva'n inverter for this but it's worth knowing what typical usage would be, so adding up the ASHP, base load etc. and also getting into the habit, if you can, of only using high usage appliances serially rather than all together. That way, it will only occasionally mean that you are drawing power from the grid at the expensive rates.

It depends - as with many things.... Your base load will be between 250W and 500W depending on the time of day - more lights on more base load. There are many people on the forum that have their base load down to very small levels by disconnecting all wall warts etc. But let's say you're a typical family, so between 250W and 500W. The ASHP will draw it's 4kW continuously unless it's doing a defrost, when for a short period, it will draw a lot less. Your oven will draw about 3kW until it's up to heat - 5 to 10 mins? Then will turn on and off at 3kW when it needs more heat. Induction hobs tend to turn on and off repeatedly - more often on a higher setting. So assuming everything is on, that's at least 500W + 4kW + 3kW + 3kW as a maximum - 10.5kW but only 4.5kW is continuous. 2 x 3kW is on and off. If you have let's say a 4.5kW inverter, then each of those 3kW has to come from the grid, so at the expensive rate as it's during the day. And we've not taken into account the dishwasher, washing machine and EV charging.... If this is the case and I'm not sure it is, it could be because the maximum PV you can install without contacting the DNO is just less than 4kW, so a smaller inverter would match that. However, if you have a battery system sized for your typical consumption, in our case 15kW, then a larger inverter makes sense and means we almost never take peak priced energy, it's all at the 7p Oct Int Go rate, because we load the batteries at night and our solar does the rest. As for most appliances drawing a peak for a short time, this is true for washing machines and dishwashers but not for ovens and induction hobs and EV chargers and ASHPs draw at the peak rate all the time. And even dishwashers and washing machines can draw 3kW for 5 or 10 minutes as they heat the water. Hopefully your experts will be expert.... What's right will depend on the appliances you have, how often they are used, what your base load is and also, what you want to get out of this. Do you effectively want to only use cheap rate electricity, or is the plan to reduce as much as you can your use of higher rate at a reasonable rate of return for the investment. EDIT PS - the power output of your ASHP is the higher figure, the electricity usage is the lower figure

We had no issues with our mainly corrugated metal roof and cladding timber frame. Also partly timber and render clad. Although we didn't need a mortgage for the build or now. Our insurers weren't interested but put us on to Gallaghers who found an underwriter for us. Bit more expensive but not much. Timber frame is great for getting the frame up, windows in and watertight. If we ever built again we'd go this route.

Too late to do an edit...... @Archer - you were the OP I think - and I know you said my post was useful, so please take note of the above second thoughts......

Rob, I need to go back and edit my post - I was thinking about this yesterday and actually, I'm pretty sure, the real reason for having a larger inverter is if you have more PV than the 3.7kWp (or whatever the number is that you can install without having to talk to the DNO), then you need a larger inverter because they top out at their maximum rating. The usage thing isn't actually that important - especially if you can get the other half to work serially rather than having everything on at once. We have a 5kW Sunsynk and a 6.5kW ground mounted array - in the summer, the Sunsynk tops out at around 5.4kW, so we lose some PV. Not a lot in our case, as the array is at 45deg, to give us lower summer output and higher winter output. We had a standard inverter on the array before we installed the batteries and this was larger and didn't top out. So I should have written above that it depends on your PV array - apologies to anyone I've misled on that - I'll go back and edit the previous post.

Ah yes - I remember this now... Getting old, memory not what it was. Doesn't work for DIY installs though, you have to have a supplier do the install to reclaim the VAT - or, I guess, have a friendly sparky that will do the paperwork for you.

Check out the price on ITS Technologies - £690 + VAT. It pays to shop around....

Friends found one of those - he managed to set things up so that they never seemed to use any Solar and the battery never discharged - not sure how he managed to do that. DIY is pretty simple if you are competent and trust yourself - and AFAIK, doesn't need a sparkies sign off, if everything is connected to an existing properly rated spur that has been signed off. Someone will be along in a bit to either confirm this or tell me I'm wrong. The Sunsynk inverter above, may not be man enough for many homes, ideally you want one that can supply enough power for a couple of big white goods needs, so something closer to 6kW. Also, look at the Sunsynk batteries. The last time I checked these were cheaper than Frogstar. And in terms of battery sizing, you need to match the amount you might need to cover at the higher rates, if you're installation isn't big enough, you'll still be using expensive electricity. There are a couple of other good sites TradeSparky and ITS Technologies with products from many suppliers. We bought and installed a Sunsynk 5kW hybrid inverter and 3 5kWh batteries from ITS for £5k inc VAT. Works very well for us with the 6.5kW Solar array. Loading everything at night on the 6 hours of Int. Octopus Go, means we very rarely use any full price electricity, it's all at the 7p night rate. One thing to think about, is that Solar installs can be zero rated VAT, if done by a sparky (not sure if it has to be an MCS sparky). So you could 'install' 1 panel and get the VAT back on the whole installation. Also, not many systems can cover you during a power outage - Telsa and some others can - if this is important, then make sure you've checked this.

Take a look at the specs for either the Shelly device above, or the Sonoff mini. It's very simple, from memory, you take the power and switched live from the wall switch, put them on the wifi switch and take leads from the wifi switch to the wall switch live and switched live (and maybe a neutral). Once you switch the circuit back on at the CU, you can search for the new device in the app. Also, Sonoff do versions for Zigbee as well as wifi - I think zigbee has a better range and is less susceptible to a poor signal. I might be wrong there. If you do go Zigbee, you'd need a Zigbee to wifi bridge to get the devices visible on wifi. Buy one and have a play... they're very cheap. EDIT - if you can wait, go on a Chinese site, they are cheaper there than Amazon. And there's black Friday deals around at the moment.