Now that we are over our first winter in our new house I have been taking a look at the running costs.

The house is 1.5 storey 215m^2 with 0.9 windows and all other u values under 0.1

The PHPP assessment suggested a heat demand of 22kWhr/m2/a or a total of 4400kWhr (PHPP considers the "treated floor area" to be just under 200m^2)

By taking our March electricity consumption when we had no heating on away from our Nov, Dec, Jan & Feb. consumption I deduce that our actual heating demand was 2,702kWhr. (That does make some assumptions about our non space heating energy use but on balance I think it is a fair assessment).

My wife's comment is ringing in my ears "I was expecting it to be cheaper to run".

All the way through the build I have made decisions on the spec. based on economic value. Nothing was chosen if it didn't offer a reasonable payback.

As we do not have mains gas and I took a personal decision not to burn wood to heat the house we were left with choosing some form of electrical heating.

The capitat cost of a GSHP ruled out any reasonable payback and with our low projected demand the payback period on an air to water heat pump was around 12-14 years probably longer than it's lifetime and allowing nothing for servicing or breakdowns.

So thus we have ended up with a simple direct electric system for space heating and DHW.

I don't have a meter on our DHW consumption so I am assuming it to be 3600kWhr/a so our total consumption for heating and DHW this year should be 2,700 + 3,600 = 6,300kWhr

So what if we had chosen to go for a lesser specification for the fabric and used the savings towards a heat pump which would be justified on the grounds of the higher demand, what would our running costs be then?

Here in the south of Sweden where the house is located the building regs demand a maximum space heating demand of 55 kWhr/m2/a

So if our house was built to the regs the space heating demand would be 215 x 55 = 11,825kWhr + 3,600kWhr for DHW gives a total of 15,425kWhr.

If this total was supplied by an Air to water heat pump with a SPF of 2.5 ( which I think is perfectly reasonable) then the total energy consumption would be 6,170kWHr.

That's marginally less than our actual usage.

The question is of course what would our savings in capital cost have been if we had just built to the regs?

Hard to say exactly but I reckon we could have saved about £4,000 on inferior foundations, possibly more, at least another £2,000 on inferior windows and doors and another £2,000 on insulation. More than double the cost of adding the heat pump.

So by building to a lower spec. we could have built at cheaper cost and had marginally lower running costs.

I do now intend to offset the majority of our electrical consumption by adding 6-10kWp of PV but ironically if I had built to a lower spec. I would have saved about half the cost of doing so.

Of course all of the above reflects our own particular set of circumstances and the figures will vary from house to house but it is perhaps food for thought for those considering a new build.

It is the same dilemma I have about 'upgrading' to an ASHP, just not worth it financially.

Not sure what the problem is - "I was expecting it to be cheaper to run".

2702kWh for the 3 coldest months looks to be well enough in line with 4400kWh target for the whole year?

@Tom We are living in the house since September, no heating on in October and off again on the 1st. or 2nd. of March so the 2,702kWhr is our total for the year so well below the 4,400kWhr estimate.

It could be argued that the undershoot is due to the mild winter and that in a harder winter we will be closer the estimate of 4,400kWhr but that only gives weight to the argument of building to the regs and not lower.

Given the milder winter perhaps the house built to regs has performed at 45kW/m2/a rather than 55 so the total consumption would be 215 x 45 = 9675 + 3600 = 13,275 / 2.5 = 5,310kWhrs against our 6,300kWhrs.

Or in a year when both houses performed to the estimate the figures would be:

4,400 + 3,600 = 8,000kWhrs.

Vs.

215 x 55kWhrs = 11825 + 3,600 = 15,525 / 2.5 = 6,170kWhrs

Are there other factors such as airtightness that can affect the performance more than you think.

Posted By: Ed DaviesIn other words, trading insulation for a heat pump wins because you get the benefit of the heat pump for the DHW as well.

But you need to factor in the replacement of the heat pumps over Tony's 100 years or so. The insulation will, hopefully, just sit there.

Very true. Answers my previous question! I can tell the wife that she can look forward to never having to face the cost of replacement heat pumps for the rest of her life.

Posted By: SteamyTeaAre there other factors such as airtightness that can affect the performance more than you think.

We have a very good level of airtighness in the house, measured at better than required for PHI certification and I am of the opinion that airtightness is a big factor in the house performing well.

My first thought was in line with @fostertom - that doesn't look to be very out of line. And my comment would be to plead "insufficient data" and continue to monitor for a full year, or whack the large amount of solar up quickly and then re-monitor to see what happens to the numbers.

I'm interested in the 'Swedish' understanding of "expensive to run", even for a passive house, and I wondered if it was because of sky high electricity prices.

But according to the Beeb last November in Stockholm (is it the same everywhere?) electricity prices are 30% below the European average at 0.13 euro per kWh. Is that about right for you?

In itself that is an interesting influence, especially on viability.

That looks like an annual bill of 820 Euro or less than £700 based on your prediction.

Within a figure that low, I'm not sure what scope you have for 'economic payback'. Are you back to logs or 'loadsa solar'? Perhaps you need more expensive electricity .

Ferdinand

Pic ref: http://www.bbc.co.uk/news/business-25200808

I can almost hear the collective groan as I mention A2As again, but... why didn't you consider getting a couple, especially since you've had them before? Did you find them noisy/uncomfortable?

They seem to be, max, 1/3 the price of an A2W (at least in the UK) and perform 60% better at space heating (4.0 SPF in Malmo according to the consumer data you showed me), so the economics should be very favourable compared to using straight elecricity for heating. Unless DHW is a very high proportion of your demand now?

The lifetime of an ASHP (whether A2A or A2W) should to some extent depend upon the running time. If the smallest heat pumps available (around 5kW output) cover the demand of both the well insulated & built-to-regulations house then should we assume a longer life in the former case? You could even argue that the life of an ASHP in a benign environment should be measured in kWh of heat delivered. I don't have any reliability data to back that up, but if it were true then the return on investment argument goes away.

That said, I don't think we should be looking just at the financial cost. Especially in the UK, where the electricity is relatively "dirty" from a CO2 point of view, we should also be looking at the environmental impact. Does it make sense to continue to consume more electricity & thereby emit more CO2 for the rest of the life of the house because the financial return on an ASHP does not make it financially attractive enough? I think we may be guilty of wanting our cake and eating it.

David

@ferdinand

As in the UK the electricity market is deregulated here in Sweden so we get the bill in two halves. One to the network operator and one to the electricity supplier.

In terms of the network operator (E.ON) the country is broken down into different sections and here in the south we have the highest charges which are considerably higher than for the Stockholm area. There is a standing charge which varies according to the size of main fuse. (per phase, every house has a 3 phase supply)

For my area the standing charges are: 16A 312.5kr/month 20A 413.75kr/month and 25A 536.25kr/month

For Stockholm they are: 16A 192.50kr/month 20A 278.75kr/month and 25A 378.75kr/month.

In addition to that we pay the network operator a delivery charge for every kWhr delivered. In my area it is 0.2kr/kWhr and in Stockholm it is 0.125kr/kWhr.

There is also a charge of 99kr a month just for the pleasure of being their customer.

All those include VAT at 25%.

Then to the electricity supplier (which in my case happens to be the same company E.ON).

We pay a variable price every month per kWhr of electricity, in last months bill the price was 0.387kr inc Vat @ 25%

Then there is an energy tax of 0.293kr/kWhr which also gets 25% VAT bringing it to 0.366kr/kWhr.

And another 28.54kr a month for the pleasure of being their customer.

So in last months bill the total price I paid per kWhr worked out at 1.43kr which at today's exchange rate works out at 13 pence Sterling. The current exchange rate is around 11SEK to 1GBP.

I am currently in a similar position in deciding whether to proceed with the installation of an ASHP to replace an EAHP. Our electric consumption with the EAHP for DHW and heating is 8700kwh/yr. 5000kwh of that is immersion. By changing to an ASHP i both reduce my heating demand and overall electric consumption down to between 3600 and 4200kwh/yr for DHW and heating, depending on the SPF used to calculate savings. I therefore have the potential to save around 5000kwh/yr. A fully installed ASHP will set me back £8k, so a 12 year payback without RHI and a 5 year payback with. I wouldn't be considering an ASHP if it wasn't for RHI support. It will bridge the gap and allow me to come into line with those fortunate enough to be able to connect to mains gas.

It is often commented that when heating demand is the same or lower than DHW it doesn't really matter what fuel source and system you use. My experience and this thread certainly seems to disagree with that thought. £600 a year is not to be sniffed at and I would far rather decide how to spend the money than it to one of the energy companies.

For us the investment in insulation was worthwhile as it significantly reduced our energy requirement compared to what it would have been if we had built to minimum regulations. It does however, make the choices in terms of heating and DHW a little more complicated as payback starts to come into the equation due to the inflated costs of certain technologies. On balance I think it right that we try and minimise or energy use. Also worth bearing in mind that at some point in the future we will be specifically taxed on the amounts of energy we use.

If you build a highly airtight/well insulated passivhaus style house, but DONT use an ASHP type ventilation/heating system , are you really going to see the true benefits??

Even ignoring the environmental argument, it just doesn't seem right to reduce your energy consumption by a factor of 3, only to throw it all away by using direct electricity.

So what if the payback period is longer? Does the ASHP pay better than the same money in a savings account? If you have a mortgage, does the cost of borrowing exceed the rate of return? If maintenance & replacement costs are the concern, then won't a given heat pump last a lot longer in a low energy house than a house built to building regulations?

I think we on this forum can be prone to over-analysing things; sometimes you just have to do what's right. If we don't then what chance is there that everyone else will?

David

Apologies to harp on, but would -really- appreciate your opinion on A2A. Why a non starter for you?

Posted By: bot de pailleWhat do you mean Chris.P.Bacon by this?? I dont understand.

I think that Chris mean that at low energy usage levels the capital cost of alternatives is too high. It is easy and cheap to heat say 100 lt of water with electricity but very expensive to do it with a heat pump.

A simple example is making some tea, I can get a 10 quid kettle and put 5p worth of dirty electricity into it and make a pot, or I can get gas connected at £20,000, then buy a £400 stove, then a £10 kettle and put 4p worth of gas into it to make the pot.