With Treasury pressure on funding, it is unlikely that the Govt. will top up the total amount available this financial year, as has happened in the past. With the remaining funding looking like it will run out short of the end of the financial year, and pressure for cuts to the overall budget (just under £2 billion allocated for the financial years 2027/28 to 2029/30), it would make economic sense to cut the amount of the grant. That way the limited funding remaining for 2026/27 can support more heat pump installations, and cuts could be made to the budget for subsequent years, while still notionally supporting the same number of heat pump installations. 

https://www.ofgem.gov.uk/data/bus-monthly-scheme-update as published 13th Oct 2026.

Changes to the grant can only take effect 28 days after they are published. So if there is a change at the budget, there should at least be a limited time for those well advanced in the process of getting a heat pump to access a voucher at the current rates.

If the BUS grant is reduced, and the gas standing charge removed with the costs placed on the unit rate, then the case for air-to-air as a hybrid solution providing space heating and cooling alongside limited use of gas (for central heating, hot water, and cooking) is going to become compelling. 

if you have a PV inverter and either sun or charged batteries, and the electricity provider is limited to 25kVA

Not so any more....

1: It's now the case that the Service Fuse will be 80A, not 100A.

Each DNO will have issued their own directive (known as a Standard Technique) which specifies this.
Read this one from National Grid (NGED).

For three phase domestic supplies, the Service Fuse will normally be 60A per phase for a domestic customer.

2: The "designated voltage" for 1ph is 230v. See sect.27 of the Electricity Safety Quality and Continuity regulations.
DNOs are now starting to change the taps at Primary substations in order to reduce the usual 240v we have grown used to.

This change has still not been fully ratified, but is agreed on by members of the Electrical Networks Association (ENA).

80A x 230v comes to 18.4kVA.

3: If your continuous loading is calculated to exceed 60A (not the 80A fuse rating), there are circumstances by which the DNO can require you to accept a 3ph supply.
The reasons are complex, but pay particular attention to the Neutral current and you'll begin to understand the issues.

The whole point of 3ph is that the load on those phases should be even.
That being so, no current flows in the Neutral.

Deliberately designing a supply for a new house which causes large currents in the neutral will create thermal stress at the local substation.
That causes breakdown of insulation, and hence a higher risk of outages.

4: If the reason you are applying for a single-phase supply greater than 18.4kW, but not more than 23kVA, is due to an EV charger, then it may not be fixed to the building.

The charger must be fixed to a separate/dedicated post, with the position dictated by airflow for cooling.

Talk with the Network Planner in the DNO Team assigned to your area.

They use a software calculator which takes into account a number of parameters which you won't know about.

Posted by: @e-a-west

Ideally I would prefer a complete package, ASHP, PV, battery etc, so that they all align.

It might be worth taking a look at the Octopus zero bills initiative. I think your house would easily qualify in terms of the level of insulation that you have planned.

As its says in their PR,

"A Zero Bills home is a regular house with good insulation to make it energy-efficient, and it's then fitted with solar panels, a heat pump, and a home battery. These technologies work together to power the home, and our tech platform, Kraken, manages it all to make sure the energy is used in the smartest way possible."

"Residents do not pay a penny for the energy their home uses and there are no standing charges, for at least 5 (but usually 10) years. There is a generous fair use allowance, which is the amount of energy usage included in the guarantee (set at roughly double the average household usage). The only exception is that electric vehicle charging is billed separately at our super low Intelligent Octopus Go rate, which automatically charges your car at the cheapest rates, creating a complete clean energy ecosystem."

https://octopus.energy/blog/explore-zero-bills-home-customer-interview/ and many other pages that you will easily find via google.

I have no experience of this myself. Rather, I am mentioning it because it seems to fit the bill in terms of integration and easy of use. In theory, it would be fit and forget. Nothing for you to manage once installed and zero energy bills for ten years, plus EV charging at very competitive rates.

Note if you have a PV inverter and either sun or charged batteries, and the electricity provider is limited to 25kVA, your actual limit before it trips is 25kVA + whatever the inverter can output. That requires a bit of thinking about the panel, since the distribution must be sized to carry the whole current.

Also consider a smart EV charging station that will exploit PV and also monitor total VA drawn from the grid and reduce charging power to avoid tripping when needed. This is a basic function, most of them do it, but Rule #1 of PV is "nothing is compatible with anything" so you must check first before painting yourself into a corner. Some of these "smart" devices will not even charge the car if the internet is down, a process known as "enshittification".

It goes without saying that the EVSE will want its own smartmeter, which will be incompatible with the smartmeter your PV inverter is married to, both being extremely overpriced variants of the exact same product you can get for very low cost on aliexpress, but with slight protocol variations to make sure your money becomes their money. 

Most "smart" EVSEs are ridiculously dumb and require manufacturer cloud access for even the most basic functions like timed charge or PV optimized charge which means it will no longer work when the manufacturer unplugs the servers, or they will decide to charge a monthly fee at some point. If you do not want to waste money on a garbage product, please check https://evcc.io/ and pick an EVSE that can be controlled locally using ethernet or modbus. They you can use evcc or home assistant or anything else.

Put a conduit of the correct size plus one between the panel and the EVSE, then another for control, then another just in case.

With a near passive house new build, consider ducted air to air heat pump. It also does cooling and air conditioning, which is nice when PV delivers "free" power in the summer, and heating COP is excellent. Ducted is problematic when the required heating power is huge because that requires moving an equally huge amount of air through ducts, which means enormous ducts and/or noisy fans. But with your low heating power requirements, there is no such drawback as long as the cooling power requirement is also reasonably low (shading, protection against sun on windows, etc).

Given current climate trends, in a well insulated house, cooling requires more power than heating, so the heat pump ends up sized for cooling and oversized for heating.

If, in the meantime, anyone has suggestions of highly regarded suppliers/installers in the Suffolk area please let me know, or possibly point me in the right direction on the Forum.

 "A little knowledge is a dangerous thing" springs to mind with where I was at with it all before joining here. Thank you all for your very detailed input. I shall be back with more questions no doubt.

The whole thing is a complete mess though. Like many countries we have a system that pulled a lot of fixed costs out of the fixed part of the bill and hid them in the unit cost so that it notionally helped poorer low users. Today the skew of bad housing and inefficient heating is strongly towards poor people so it doesn't actually work properly. Moving them all onto unit charges is basically taking money from poor people and giving it to the well off, holiday home owners, foreign investors who hold vast numbers of our houses empty as just numbers in a spreadsheet and so on. (We've got 350,000 long term empty usable properties in the UK mostly held as "investments", many by people who've never visited the UK, let alone by rubber dinghy).

The even bigger problem though is the end of gas problem - and this makes it worse. If gas disconnections continue to randomly distributed, or worse yet everyone "mostly disconnects" the fixed costs of the gas network have to be covered somehow. That drives gas prices up which drives disconnections up but not in a way you can shut down any large pieces of the network. All the economic modelling basically says if you allow that your gas operators go under and you get a multi-billion pound a year bill to keep the mess running with pretty much no way out.

And unfortunately discussion about "turning gas off area by area" which is actually needed is so toxic our governments desperately kick the can down the road.

No G100 limits your grid tied not grid connected inverter to 3.68kW. That's a really important distinction and plenty of farms for example have really big grid connected but not grid tie inverters. There are ways and means to work around this, either by just not exporting in the first place (grid connected inverter only - effectively offgrid but with the grid as a generaotr input), and splitting things between a 3.68kW grid tie inverter that's fielding your exports and a big non grid tie inverter that's running the house. That does add a lot of complexity though.

Agree with Rob on the battery to some extent but you would still need to plan all the stuff that matters with battery in advance and you've then got to pick a hybrid inverter that supports batteries but can run without them - which narrows the field somewhat. The battery location rules are complicated and they really determine where the inverter goes. If you want to do house backup you'd also want to wire once so that you've got the essential loads split from things like the EV charger, power showers, oven etc.

Certainly battery prices seem to be on the down and everyone is predicting they'll continue to fall in price and improve.

If your proposed hobby room may include any 3ph machines (lathes etc) you can use a VFD to provide a usable 3ph supply from 1ph.

If theres multiple machines needing 3ph, a rotary motor, generator setup could be an option to power the workshop.

I come back to my earlier point about progressing slowly on this. There is a lot to be said for getting settled in and then later looking at whether solar and batteries are worthwhile given the circumstances. If you don't have an EV yet, then £9k saved on not going for 3 phase plus circa £15k saved not installing solar and a battery buys you quite a nice new EV. That would do far more for your overall CO2 emissions than the addition of some extra solar generation and battery storage. 3p per mile running costs vs 15p per mile for an economical petrol car likely also does far more for your bank balance than limited solar exports.

Your house will be so well insulated that when it needs heating, you can simply boost the temperature slightly during cheap rate electricity periods and the building's thermal capacity and insulation will ensure that it stays within a degree or so of that temperature before the next cheap rate period arrives. Most heat pump tariffs provide two or three cheap rate time slots throughout the day, so this approach will work very well for you. That way, you'll be running your heating on half price electricity even without any solar and batteries. Of course anything that also runs in the cheap rate time slots also gets to use half price electricity, for example putting the washing and dishwasher on in the afternoon 1pm to 4pm slot. Once you've had a year of actually living in the house, you'll have hard facts about your actual electricity usage and be able to properly model whether or not solar plus batteries are worth the capital outlay. It is quite possible given your somewhat unusual circumstances that they might not be and your money would be better spent elsewhere.