Large house, 3 phase electric but sky high bills! Help please?

markin

The pool will be at least half the usage, if you can't see a huge difference in daily/hourly readings then maybe you aren't turning it off correctly.

Check with all fuses off apart from the solar that the solar isn't counting up the meter with its export.

Post lots of photos! imgur.com is a good free site. Redact the Serial number from the meter photo.

born_again

Mrcsmrs said:

The pool being on or off doesn’t seem to change our usage but I don’t know what the ratings are. I will ask husband to check it out. 

Thank you. 

That does not sound right. Anyway to totally isolate the supply to the pool room?

Then checking usage figures over a few days before, during off & after to see how they change?

Ectophile

A competent electrician who's familiar with 3-phase electrics should be able to go through the house and work out what breakers feed what.

They should also have a clamp meter to measure how much current is being drawn by each circuit.  If one is drawing too much power for no obvious reason, then that will probably identify the problem.

gm0

You get lots of free electricity units in spring to autumn from your solar.  If it isn't offsetting consumption to (mostly) heat the pool (assuming this is set to be timed to happen daytime). And should provide all the daytime light household use all summer. If 10kW of panels isn't contributing then something is broken or switched off between panels and inverter and the rest. Get it checked.  Understand the isolators, the meters, switches, inverters.  All this is *yours* with the house.  Nobody else is responsible for it.  Electricity supplier is not involved.  Does not care.  Hire an electrician as needed to check it and explain it to you.  This could be a professional install (from a still trading installer who may help a bit in return for being hired for heating servicing. Or some mad retiree DIY affair - which will be either brilliant or terrible - but unsupported either way.

In contrast you get about 1/10th as much solar in winter.  So it won't make a substantial dent in your heat pump heating costs.  All that will be paid for at today's energy prices which are not the same as when these heat pumps were likely fitted.  Hence your shock.

But after checking solar is indeed working and deployed sensibly - This is likely about heat pump heating in the winter and relationship of that to the heat load of your building at a given temperature inside and out

The combination of UFH and ASHP is beneficial. Yet the efficiency of heat pumps has improved over the years and settings and maintenance of them can matter a great deal.  Validating this could help you reduce your bills by a decent % if it lacks maintenance or has been setup poorly.

Find out what they all are (and the electrical plate "rating" of each).  Look up online efficiency data.  Consider whether yours are running to their full potential at a sensible (low) temperature and are operating efficiently for what they are in terms of the technology

A possible problem with heat pumps and converted buildings is that the operating temperature on them is turned up too high because the peak winter heat load is higher (due to poor insulation and draught proofing) than the system truly copes with. So people are cold and "turn it up".  Or the installer tweaks the setting vs doing something more expensive (for them) to rectify a design but at the expense of running cost.  When these systems were installed long ago - perhaps it a tad undersized.  Or your heat load has gone up - draught proofing and blown double glazing units. 

Perhaps it runs long and too hot.  Or it is fine and the heat load of your large building - just is what it is.  Until you address insulation more fundamentally.

Supplementary heating at peak is a better approach, leaving the heatpump system configured efficiently - for most of the heating, most of the time with the most COP (heat kWh out as multiplier of electricity kWh in.  This efficiency goes "down" as you turn up the temperature of the water flowing around the UFH. 30-35C likely good.  50C likely bad.   Find a thermometer on the manifold (water pipe distribution) or at the heat pumps and look at it when running a while.  Again get someone to service it and explain it to you as the new owner.

Cost worked example:

Assume 2x 10kW heat pumps running 24x7 for 6 months at 50% duty cycle

First approximation:  (365 days / 2) * 24 hrs * 2 pumps * 10 kw * 0.5 duty = 43,800 kWh per year.  For heating from the heat pumps - delivering 2x to 3x as much "heat".
At <10p that wasn't so awful context size and type of building.  At 30p-50p it is.

Now unless your conversion is rather poorly insulated and sealed or you sit with the windows open the 50% duty cycle may be a poor assumption in the above calculation.  But high heat losses are not uncommon with barn conversions.  Many lack the couple of feet of loft insulation found in normal buildings due to exposed internal roofs and the absence of false ceilings.

The size of the pumps is what it is.  The rest are just fixed numbers.    If the system is struggling with the building losses then the duty cycle *could* be high.  Measure what is going on.  Get what data is available from the controllers.

But be prepared for the possibility that there is no "fix" beyond extending swing season (wood stove in cold snaps) before system goes on.  And a sweater and a lower target temperature for living spaces.  If you want a "lower heat load" for the building then you will have to look at each possible improvement on what is there - walls, roof, glazing for cost, potential and disruption.

If your solar is grid connected you have likely been correctly told you cannot drop back to single phase as you likely have more solar than your network will like on a single phase (typical 4kW panels).  And have more stuff than a 100A load.  Big building and single phase restricts what you can do about ASHP, Car chargers, pools etc. 

But as you have found 3ph is not widely supported with the more attractive domestic offers aimed at the majority.  And while this may improve over time - it will be *very* slow as it is not a priority for suppliers who are driven by what the regulator is telling them to do - which is to get single phase smart meters rolled out.  You are in a tiny niche group.

Qyburn

As far as I can see a conventional two oven Aga puts out about 1kW heat to the room. That's not going to make a big impact on heat requirements for much of the house. Four oven fuel consumption is around 25% more so maybe puts 1.25kW.

shinytop

If the property needs 2 ASHPs then it's likely your heat loss is more than the maximum for a domestic ASHP, which max out in the 14-16kW range. More than 16kW would be a lot for a house.  Your house is big but not excessively so and reasonably modern.  Do you have very high ceilings?  Is it solid walls/floor? As @QrizB said, your consumption is feasible but I'd guess to use that much, your ASHPs are probably running inefficiently.  As has been suggested, some info about the make/model and setup would help. I assume you don't have heat loss calculations.  If your system was registered with MCS/subject to Renewable Heat Incentive (RHI) you should be able to retrieve this and other information.  

Pools get a lot of blame for high power consumption but your large solar array might cover that in the months you use yours. 
 

Qyburn

I was wondering if that 3,500 sq.ft is the footprint of the building, not the floor area (assuming at least two floors). The reason for wondering is it's only around twice the size of our place, yet includes a self contained annex and a swimming pool. 

QrizB

I don't think @Mrcsmrs has been back to the forum since shortly after posting on Friday. It would be good to hear from them again; perhaps they can fill in some of the blanks.

MeteredOut

Mrcsmrs said:

<snip>

 Our electricity usage seemingly doesn’t vary between winter and summer, whether the pool is running or not. 

<snip>

Some great responses, but can I just focus on the above for when the OP responds, as much of what has been said might change if "seemingly" turns out to be a wrong assumption.

Mrcsmrs, how is that being determined? Is that from real meter readings, estimated readings, monthly direct debit amounts etc?

Can you post your monthly kWh usage for the past, say, 12 months?

markin

Email notifications are currently broken, Could be some some before they come back to check.