February 23, 2024

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

Economic system 7

As an all-electric home, it was essential to maneuver to an Economic system 7 meter which occurred a number of months after we moved in. This provides us separate Day and Night time charges for our electrical energy. Sadly sensible meters aren’t obtainable in Northern Eire but so there are at present no choices for half-hour metering, demand facet response or agile tariffs.

One of the best 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 automobile charging is completed on the evening price and our Siemens sensible home equipment embrace a Delayed Begin operate which has allowed us to set our washer and dishwasher to run through the cheaper price too (we hardly ever want to make use of the dryer as garments dry simply within the heat environment in the home).

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

The darkish blue traces right here characterize the quantity of vitality we used on the cheaper price, and it’s straightforward 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 evening price, with the height in December at 48%.

Pricing & Hundreds

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

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

  • Day Charge £0.1699 / kWh
  • Night time 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 numerous 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 sit down round 900 Watts. In order that’s round 22kWh per day earlier than we flip the rest on. I’d prefer 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 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 residence 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 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 choice 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 evening price too, utilizing the thermal mass of our block development, tiled flooring and inside stone wall to launch the warmth through the day. We’ve experimented with a few of these methods during the last yr, tweaking issues to maneuver as a lot as doable into the evening price, while sustaining consolation ranges through the day.

The warmth pump additionally gives 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 just a little vitality within the ‘All the things Else’ a part of the information under, for the uncommon event that the system activates the immersion heater if the warmth pump can’t 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 models 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 increased COP than our air supply unit.

The system briefly 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 right down to 45°. The chrome steel tank is rated to lose round 1° each 4 hours so, if unused, ought to take nearly 40 hours earlier than it cools again right down to our regular 45° goal.

Loxone heating schematic for ASHP

The Loxone system additionally permits us to observe the standing of most of the heating’s parameters, together with the compressor’s energy, pump velocity, movement 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, nevertheless it has proved to be very helpful.

Annual Heating & DHW Utilization & Prices

Whereas we’ve precise vitality utilization figures for the warmth pump, I at present don’t have any straightforward option to break down what was on the evening price versus day. So I’ve used the annual common break up in our payments for this (64% Day, 36% Night time). This ought to be the worst case state of affairs as the warmth pump is biased to run over evening greater than by way of the day.

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

It’s price declaring that I started recording this knowledge round 6 months after we moved in. Don’t be disheartened in case you are seeing excessive vitality prices together with your warmth pump and also you’ve simply completed constructing, as usually vitality consumption might be increased as the home dries out. Likewise, don’t choose your warmth pump payments from a single month as there’s a massive variation throughout the yr. See the fitting hand column within the desk under for our breakdown.

When it comes to single days, the 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 Power 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 house heating and sizzling water, from all the things else.

You’ll discover a rise in consumption in March the place you’d have anticipated it to fall because the climate continued to heat up. This was as a result of our son got here residence 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 further vitality consumption (rattling that PS4).

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

All the things
% 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 Power Utilization – 16,276 kWh / £2,273.60
  • Month-to-month Common – 1,356 kWh / £189.47
  • Each day Common – 45 kWh / £6.23

Keep 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 automotive.

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 stable gas as a secondary methodology). In our earlier residence, 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 previous home was an identical dimension, 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 previous payments and so they 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 high of this we used about 10,500 kWh of electrical energy yearly too, giving us these comparative totals;

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

In financial phrases then, we’re spending nearly 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 development employed fundamental ranges of insulation and no airtightness measures. The brand new home is heat evening and day, in each room, we all the time have sizzling water on faucet. It’s arduous 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 diminished 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 reality 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 yr components guarantee (3 years labour) so hopefully there will probably be no main surprises any time quickly. Nevertheless, upkeep is the one side of the equation that we’ve no knowledge on and it must be thought of.

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 models. We’ve not seen any of those points. The pump could reverse on a number 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 up to now).

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 information for this publish during the last 12 months and the final third of 2021 noticed unbelievable vitality value rises. Whether or not you might be 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 may finish in the summertime.

We needed to lower our Photo voltaic PV plans through 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 ought to be considerably diminished. 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 residence) would have nearly halved our invoice for that month from £164 to round £86.

Solar PV System

A home battery remains to be an fascinating choice too, both to retailer photo voltaic manufacturing or purchase cheaper electrical energy at evening to be used through the day. As vitality prices rise, payback instances for these applied sciences lower. And it’s not all the time in regards to the cash both, for some there will probably 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 fascinating choice sooner or later too.

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


It’s essential to level out that these financial savings aren’t simply because we’ve an electrified heating system. The insulation and airtightness measures within the new home are 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 residence 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.

If you’re constructing or renovating and going the additional mile together 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

Keep in mind to check out our Instagram to observe the mission, 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.