April 12, 2024

Final August we took a have a look at a few of the choices that led us to construct a low vitality house. Now that we’ve been by means of our first full calendar 12 months, it’s time to disclose our vitality invoice and see how issues are understanding. 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 vital 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 good meters aren’t accessible in Northern Eire but so there are at present no choices for half-hour metering, demand facet response or agile tariffs.

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

Siemens Smart Appliance - Delayed Start washing machine and dishwasher

All our electrical car charging is completed on the evening price and our Siemens good home equipment embody a Delayed Begin operate which has allowed us to set our washer and dishwasher to run in the course of the cheaper price too (we hardly ever want to make use of the dryer as garments dry simply within the heat ambiance in the home).

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

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

OpenEnergyMonitor Graph

Throughout the 12 months a mean of 36% of our consumption was on the evening price, 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 truly 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 evening, 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 below are the small print of our present fastened price tariff (together with VAT);

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

On prime of the conventional 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 Entire 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 often the bottom line appears to take a seat round 900 Watts. In order that’s round 22kWh per day earlier than we flip anything on. I’d wish to look into this base load in additional element this 12 months and attempt to scale back it the place potential.

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

Heating, DHW & Controls

The home is block development with a 150mm cavity, double glazing and has a B85 EPC score 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 going through storage gable wall.

Our Loxone house automation system controls the warmth pump by way of 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 capabilities 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 stream temperature required with a purpose 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 surface 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 stream 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 evening price too, utilizing the thermal mass of our block development, tiled ground and inner stone wall to launch the warmth in the course of the day. We have now experimented with a few of these methods over the past 12 months, tweaking issues to maneuver as a lot as potential into the evening price, while sustaining consolation ranges in the course of the day.

The warmth pump additionally gives our sizzling water right into a Joule 300 litre DWH (Home Scorching Water) tank which is put in beneath the steps. There could also be somewhat vitality within the ‘Every part Else’ a part of the info beneath, 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 a fair greater 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 evening price, 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 most of the heating’s parameters, together with the compressor’s energy, pump velocity, stream price, 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, but it surely has proved to be very helpful.

Annual Heating & DHW Utilization & Prices

Whereas we have now actual vitality utilization figures for the warmth pump, I at present don’t have any simple technique to break down what was on the evening price versus day. So I’ve used the annual common cut up in our payments for this (64% Day, 36% Evening). This must be the worst case situation as the warmth pump is biased to run over evening greater than by means of the day.

  • Whole Annual Heating & DHW Power Utilization – 5,345 kWh / £732.05
  • Month-to-month Common – 445 kWh / £61.00
  • Day by day Common – 15 kWh / £2.01

It’s price mentioning that I started recording this information 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 greater 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 12 months. See the best hand column within the desk beneath for our breakdown.

When it comes to 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.

Whole Annual Power Utilization & Prices

The desk and graph beneath exhibits our complete vitality used final 12 months 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 reside with us too (between home strikes). So we went from 2 adults to five in a single day, with all of the related additional vitality consumption (rattling that PS4).

So listed below are the vitality consumption figures for the primary full 12 months 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
  • Whole Annual Power Utilization – 16,276 kWh / £2,273.60
  • Month-to-month Common – 1,356 kWh / £189.47
  • Day by 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 ‘gas’ for the Electrical automobile.

Comparisons to Final Home

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

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

  • OLD Whole Annual Power Utilization – 57,000 kWh / £3,985
  • OLD Month-to-month Common – 4,750 kWh / £332.08
  • OLD Day by 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 might be most noticeable. The final home was constructed within the late 90’s and its conventional development employed fundamental ranges of insulation and no airtightness measures. The brand new home is heat evening and day, in each room, we at all times have sizzling water on faucet. It’s laborious to quantify the standard of life enchancment this brings. Stepping onto heat tiles on a toilet ground within the morning is fairly, fairly good.

Maybe extra importantly, we have now lowered our complete 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 information from our Airthings Wave Plus).

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

The newest 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). The truth is our bias for operating the heating at evening, 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 12 months components guarantee (3 years labour) so hopefully there might be no main surprises any time quickly. Nonetheless, upkeep is the one side of the equation that we have now no information on and it must be thought-about.

A few of the detrimental warmth pump tales I’ve learn point out that the UK and Eire have climates that aren’t appropriate for air supply items. We have now not seen any of those points. The pump might reverse on a couple of days a 12 months to defrost itself however normally the effectivity of the system is excellent (and we’ve seen temperatures as little as -6 up to now).

Observe Jan Rosenow for some nice factual info on warmth pumps and the vitality transition normally.

The Future

I’ve been gathering the info for this put up over the past 12 months and the final third of 2021 noticed unimaginable vitality value 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, this can finish in the summertime.

We needed to reduce our Photo voltaic PV plans in the course of the construct to remain inside price range, however we hope to purchase a system, maybe this 12 months, to attempt to off-set a few of these value rises. As soon as put in, prices for the brighter months must be considerably lowered. A buddy’s close by 4kWp system produced 524 kWh in June 2021 for instance, which (assuming the identical 87% self-consumption price 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 fascinating possibility too, both to retailer photo voltaic manufacturing or purchase cheaper electrical energy at evening to be used in the course of the day. As vitality prices rise, payback occasions for these applied sciences lower. And it’s not at all times in regards to the cash both, for some there might be an ethical crucial to attempt to additional scale back their emissions. Utilizing an EV for V2G (Car to Grid) and V2H (Car to Dwelling) goes to be an fascinating possibility 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. Nonetheless, Northern Eire at present provides no such assist to encourage owners to do the best factor. Let’s hope issues change right here within the close to future


It’s vital to level out that these financial savings aren’t simply because we have now 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 consultants we employed – Daly Renewables and Epitome Living. Many of the complaints I learn round warmth pumps are from tasks that didn’t have a correctly designed or fitted system.

Whereas there are many extra vitality environment friendly properties 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 snug house with infinite 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 critical have 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.