March 27, 2023

Final August we took a take a look at a number of the selections that led us to construct a low vitality house. Now that we’ve been by means of our first full calendar yr, it’s time to disclose our vitality invoice and see how issues are figuring out. I’ve separated out figures for the warmth pump versus every part else. However first a bit about our setup.

Financial system 7

As an all-electric home, it was essential to maneuver to an Financial system 7 meter which occurred a couple of months after we moved in. This provides us separate Day and Evening charges for our electrical energy. Sadly sensible meters should not accessible in Northern Eire but so there are at present no choices for half-hour metering, demand aspect response or agile tariffs.

The very best factor we will do then is to ensure as a lot of our vitality utilization is pushed into the night time fee, a 7 hour window which runs from 1am to 8am whereas we’re on GMT and 2am to 9am whereas on British Summer season Time.

Siemens Smart Appliance - Delayed Start washing machine and dishwasher

All our electrical car charging is finished on the night time fee and our Siemens sensible home equipment embrace a Delayed Begin perform which has allowed us to set our washer and dishwasher to run throughout the cheaper fee too (we hardly ever want to make use of the dryer as garments dry simply within the heat ambiance in the home).

The graph under exhibits virtually a month’s value of knowledge from the superb OpenEnergyMonitor (with extra sensors there’s a selected warmth pump measuring system accessible too, take a look at this video).

The darkish blue traces right here symbolize the quantity of vitality we used on the cheaper fee, and it’s simple to identify the 5 nights that the EV was charged throughout this era.

OpenEnergyMonitor Graph

Throughout the yr a median of 36% of our consumption was on the night time fee, with the height in December at 48%.

Pricing & Masses

We’re on a 100% renewable tariff and whereas the electrons from the wind farms aren’t really flowing to our home, I imagine selecting a tariff like this encourages the turbines to spend money on extra renewables. And as we’re operating our warmth pump, home equipment in addition to charging the automobile at night time, we genuinely are utilizing a lot of wind energy. Round 50% of all electrical energy generated right here is renewable already, with targets for 80% by 2030, so identical to with an electrical car, an electrified heating system will get cleaner and cleaner over time.

Listed here are the small print of our present fastened fee tariff (together with VAT);

  • Day Charge £0.1699 / kWh
  • Evening Charge £0.0784 / kWh
  • Standing Cost £3.54 / Month

On high of the traditional fridge and freezer masses (each A++ home equipment), we even have a lot of safety cameras, a 19″ rack with a server, 48 port PoE Swap, NAS, 6-Zone Complete Home Audio amplifier, and MVHR (even our septic tank has a 24/7 draw), so our base load is excessive. The bottom determine I’ve seen from our vitality monitor is round 725 Watts, however extra normally the bottom line appears to take a seat round 900 Watts. In order that’s round 22kWh per day earlier than we flip the rest on. I’d wish to look into this base load in additional element this yr and try to cut back it the place doable.

ASAP Air Source Heat Pump and Joule 300L Stainless Steel Hot Water Tank

Heating, DHW & Controls

The home is block building with a 150mm cavity, double glazing and has a B85 EPC ranking which ought to hit an A as soon as we add a photo voltaic PV system. Heating is from this 11kW Hitachi Yutaki M Monobloc Air Supply Warmth Pump which is sited on the rear of the home on the north dealing with storage gable wall.

Our Loxone house automation system controls the warmth pump through a TCP/IP Modbus Gateway (ATW-MBS-02). Each upstairs and downstairs use Roth underfloor heating fed from three manifolds round the home, utilizing Loxone valve actuators.

Loxone Valve Actuators controlling manifold from Air Source Heat Pump

Loxone brings three, core heating / local weather management features to the system. The Clever Room Controller is accessible from the UI, and is used to view the present room temperature, change the set factors and timing and many others. Then the Clever Temperature Controller works within the background, grouping our rooms and UFH loops, controlling the movement temperature required with the intention to obtain the temperatures demanded by the room controllers. Lastly the Local weather Controller turns the warmth pump on and off, whereas additionally contemplating the skin temperature readings from our climate station. The warmth pump itself then does its personal resolution making round when to energy as much as increase the movement temps as required.

Loxone Cabinet with Hitachi Heat Pump Modbus TCP/IP Control Interface

Inside the home, each Loxone gentle change has a built-in temperature (and humidity) sensor which we use because the room thermostats. The Loxone system can common values throughout a number of sensors which is helpful within the open plan barn for instance.

The Loxone system has been programmed to warmth the home extra on the night time fee too, utilizing the thermal mass of our block building, tiled flooring and inside stone wall to launch the warmth throughout the day. Now we have experimented with a few of these methods during the last yr, tweaking issues to maneuver as a lot as doable into the night time fee, while sustaining consolation ranges throughout the day.

The warmth pump additionally supplies our sizzling water right into a Joule 300 litre DWH (Home Sizzling Water) tank which is put in under the steps. There could also be a little bit vitality within the ‘Every part Else’ a part of the info under, for the uncommon event that the system activates the immersion heater if the warmth pump can not refill the tank rapidly sufficient.

Water heating makes use of a stunning quantity of vitality and warming 300 litres from an ambient of say 16° to our 45° goal makes use of over 10 kWh. The warmth pump’s COP (coefficient of efficiency) means we get round 3 items of warmth for each 1 unit of electrical energy consumed, so we might solely use round 3.3kWh on this instance. A floor supply warmth pump has an excellent larger COP than our air supply unit.

The system quickly raises our sizzling water goal temperature to 55° each morning at 6:00am, whereas we’re nonetheless on the cheaper night time fee, getting issues prepared for the morning showers. The goal is then set again all the way down to 45°. The chrome steel tank is rated to lose round 1° each 4 hours so, if unused, ought to take virtually 40 hours earlier than it cools again all the way down to our regular 45° goal.

Loxone heating schematic for ASHP

The Loxone system additionally permits us to watch the standing of lots of the heating’s parameters, together with the compressor’s energy, pump pace, movement fee, alarm standing, outlet and inlet temperatures, DWH temperature, in addition to the positions of the three port valve and motorised valves on the manifolds. It’s nonetheless a piece in progress, and we have to get a greater graphic, nevertheless it has proved to be very helpful.

Annual Heating & DHW Utilization & Prices

Whereas we’ve got precise vitality utilization figures for the warmth pump, I at present haven’t any simple technique to break down what was on the night time fee versus day. So I’ve used the annual common cut up in our payments for this (64% Day, 36% Evening). This needs to be the worst case state of affairs as the warmth pump is biased to run over night time greater than by means of the day.

  • Complete Annual Heating & DHW Vitality Utilization – 5,345 kWh / £732.05
  • Month-to-month Common – 445 kWh / £61.00
  • Every day Common – 15 kWh / £2.01

It’s value stating that I started recording this knowledge round 6 months after we moved in. Don’t be disheartened if you’re seeing excessive vitality prices along with your warmth pump and also you’ve simply completed constructing, as typically vitality consumption will be larger as the home dries out. Likewise, don’t decide your warmth pump payments from a single month as there’s a giant variation throughout the yr. See the appropriate hand column within the desk under for our breakdown.

By way of single days, the very best vitality consumption for the warmth pump was twenty seventh November at 39.4 kWh, whereas the bottom was an order of magnitude much less at 3.9 kWh on sixteenth July.

Complete Annual Vitality Utilization & Prices

The desk and graph under exhibits our whole vitality used final yr in kWh, damaged down into 2 values, separating the vitality mentioned above that was utilized by the warmth pump for area heating and sizzling water, from every part else.

You’ll discover a rise in consumption in March the place you’ll have anticipated it to fall because the climate continued to heat up. This was as a result of our son got here house from uni and our daughter and son-in-law got here to stay with us too (between home strikes). So we went from 2 adults to five in a single day, with all of the related further vitality consumption (rattling that PS4).

So listed below are the vitality consumption figures for the primary full yr within the new Automated Dwelling;

Every part
% of Annual Heating & DHW
January 787 869 1,656 14.8%
February 655 715 1,369 12.2%
March 607 923 1,530 11.3%
April 475 982 1,457 8.9%
Might 354 969 1,323 6.8%
June 214 905 1,119 4.0%
July 194 948 1,142 3.6%
August 214 860 1,074 4.0%
September 214 907 1,120 4.0%
October 308 818 1,126 5.7%
November 518 1,018 1,536 9.7%
December 806 1,018 1,824 15.0%
TOTALS 5,345 10,931 16,276 100%
Full year energy cost graph for air source heat pump
  • Complete Annual Vitality Utilization – 16,276 kWh / £2,273.60
  • Month-to-month Common – 1,356 kWh / £189.47
  • Every day Common – 45 kWh / £6.23

Bear in mind, we aren’t burning something, we purchase no fuel, heating oil, coal, wooden, petrol or diesel. In order that £189 (common) is our single month-to-month invoice for all our heating and sizzling water, all our cooking and washing, all our Lighting and leisure plus our ‘gasoline’ for the Electrical automobile.

Comparisons to Final Home

The latest figures I might discover confirmed that 68% of houses in Northern Eire use oil as their main methodology of heating (and amazingly 72% nonetheless use strong gasoline as a secondary methodology). In our earlier house, 900 litres of heating oil would final us round 4 to five weeks over December / January. The present price for that one fill is round £440 – over half our annual heating price within the new home.

The outdated home was an identical measurement, 275 sq m / 3,000 sq ft (together with the built-in storage) and whereas I don’t have detailed knowledge, I do have entry to my outdated payments they usually present we averaged 5 x 900 litre fills of heating oil every year. In vitality phrases, that 4,500 litres represents roughly 46,500 kWh and on high of this we used about 10,500 kWh of electrical energy yearly too, giving us these comparative totals;

  • OLD Complete Annual Vitality Utilization – 57,000 kWh / £3,985
  • OLD Month-to-month Common – 4,750 kWh / £332.08
  • OLD Every day Common – 156 kWh / £10.92

In financial phrases then, we’re spending virtually half what we did within the final home. However the financial savings are solely half the story, because it’s the rise in consolation ranges which can be most noticeable. The final home was constructed within the late 90’s and its conventional building employed primary ranges of insulation and no airtightness measures. The brand new home is heat night time and day, in each room, we all the time have sizzling water on faucet. It’s laborious to quantify the standard of life enchancment this brings. Stepping onto heat tiles on a toilet flooring within the morning is fairly, fairly good.

Maybe extra importantly, we’ve got lowered our whole vitality consumption by greater than 70%, together with all of the related CO2 financial savings and air high quality enhancements (take a look at this knowledge from our Airthings Wave Plus).

Before and After graph, showing air quality improvements in a house with MVHR fitted

The most recent figures I can discover (2019) present that 330 grams of CO2 was produced per kWh of electrical energy generated in Northern Eire. Assuming a COP of three.2 meaning lower than 100 grams of CO2 per kWh of warmth. That’s round half the CO2 emissions of a mains fuel boiler and round a 3rd of an oil fired heating system (source). In truth our bias for operating the heating at night time, coupled with the extraordinary ranges of spare wind energy in NI, means we could also be doing higher than that.

The warmth pump has a 7 yr elements guarantee (3 years labour) so hopefully there can be no main surprises any time quickly. Nevertheless, upkeep is the one facet of the equation that we’ve got no knowledge on and it must be thought of.

A few of the unfavorable warmth pump tales I’ve learn point out that the UK and Eire have climates that aren’t appropriate for air supply items. Now we have not seen any of those points. The pump could reverse on a couple of days a yr to defrost itself however on the whole the effectivity of the system is excellent (and we’ve seen temperatures as little as -6 to this point).

Comply with Jan Rosenow for some nice factual info on warmth pumps and the vitality transition on the whole.

The Future

I’ve been gathering the info for this put up during the last 12 months and the final third of 2021 noticed unbelievable vitality price rises. Whether or not you’re utilizing electrical energy or burning fuel or oil, costs have seen unprecedented will increase over this time. Whereas we’ve been fortunate to be on a fix-rate tariff, it will finish in the summertime.

We needed to minimize our Photo voltaic PV plans throughout the construct to remain inside finances, however we hope to purchase a system, maybe this yr, to try to off-set a few of these worth rises. As soon as put in, prices for the brighter months needs to be considerably lowered. A pal’s close by 4kWp system produced 524 kWh in June 2021 for instance, which (assuming the identical 87% self-consumption fee as our earlier house) would have virtually halved our invoice for that month from £164 to round £86.

Solar PV System

A home battery continues to be an attention-grabbing choice too, both to retailer photo voltaic manufacturing or purchase cheaper electrical energy at night time to be used throughout the day. As vitality prices rise, payback occasions for these applied sciences lower. And it’s not all the time concerning the cash both, for some there can be an ethical crucial to try to additional cut back their emissions. Utilizing an EV for V2G (Car to Grid) and V2H (Car to Dwelling) goes to be an attention-grabbing choice sooner or later too.

Some UK blogs speak about receiving £400 a month from their RHI scheme as an incentive to purchase a warmth pump. Nevertheless, Northern Eire at present presents no such assist to encourage householders to do the appropriate factor. Let’s hope issues change right here within the close to future


It’s essential to level out that these financial savings should not simply because we’ve got an electrified heating system. The insulation and airtightness measures within the new home are very important to the success right here. As is the involvement of the specialists we employed – Daly Renewables and Epitome Living. Many of the complaints I learn round warmth pumps are from initiatives that didn’t have a correctly designed or fitted system.

Whereas there are many extra vitality environment friendly houses than ours, we’re delighted with the efficiency of the constructing and its cleaner, quieter, low carbon heating system. We’re having fun with a a lot hotter, extra comfy house with countless sizzling water, for round half the operating prices of the oil fired home, all whereas producing far much less GHG and air air pollution than earlier than.

In case you are constructing or renovating and going the additional mile along with your insulation and airtightness measures, then take a severe take a look at electrified heating.

Are you able to afford to not?

UPDATE – see the figures for the 2022 right here

Bear in mind to check out our Instagram to comply with the challenge, learn the remainder of the Automated Dwelling 2.0 weblog posts and discover the hyperlinks to all of the merchandise we’ve used in our self-build.