Final August we took a take a look at among the selections that led us to construct a low power dwelling. Now that we’ve been via our first full calendar yr, it’s time to disclose our power invoice and see how issues are figuring out. I’ve separated out figures for the warmth pump versus the whole lot 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 number of months after we moved in. This provides us separate Day and Night time charges for our electrical energy. Sadly good meters are usually not accessible in Northern Eire but so there are at the moment no choices for half-hour metering, demand facet response or agile tariffs.
One of the best factor we will do then is to verify as a lot of our power utilization is pushed into the evening charge, 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.
All our electrical car charging is finished on the evening charge and our Siemens good home equipment embrace a Delayed Begin operate which has allowed us to set our washer and dishwasher to run through the cheaper charge too (we hardly ever want to make use of the dryer as garments dry simply within the heat environment in the home).
The graph beneath exhibits virtually a month’s value of information from the wonderful OpenEnergyMonitor (with extra sensors there’s a particular warmth pump measuring system accessible too, try this video).
The darkish blue traces right here symbolize the quantity of power we used on the cheaper charge, and it’s simple to identify the 5 nights that the EV was charged throughout this era.
Throughout the yr a mean of 36% of our consumption was on the evening charge, 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 consider selecting a tariff like this encourages the mills to spend money on 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 car, an electrified heating system will get cleaner and cleaner over time.
Listed here are the small print of our present mounted charge tariff (together with VAT);
Day Fee £0.1699 / kWh
Night time Fee £0.0784 / kWh
Standing Cost £3.54 / Month
On prime of the conventional fridge and freezer hundreds (each A++ home equipment), we even have numerous 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 power 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 yr and attempt to scale back it the place attainable.
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 going through storage gable wall.
Our Loxone dwelling 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 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 movement temperature required so as 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 enhance the movement temps as required.
Inside the home, each Loxone mild swap 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 charge too, utilizing the thermal mass of our block building, tiled ground and inside stone wall to launch the warmth through the day. We have now experimented with a few of these methods during the last yr, tweaking issues to maneuver as a lot as attainable into the evening charge, while sustaining consolation ranges through the day.
The warmth pump additionally offers our scorching water right into a Joule 300 litre DWH (Home Sizzling Water) tank which is put in beneath the steps. There could also be a bit power within the ‘Every little thing Else’ a part of the information beneath, for the uncommon event that the system activates the immersion heater if the warmth pump can not refill the tank shortly sufficient.
Water heating makes use of a shocking quantity of power 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’d solely use round 3.3kWh on this instance. A floor supply warmth pump has a good larger COP than our air supply unit.
The system quickly raises our scorching water goal temperature to 55° each morning at 6:00am, whereas we’re nonetheless on the cheaper evening charge, getting issues prepared for the morning showers. The goal is then set again all the way down to 45°. The stainless-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.
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 charge, 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 actual power utilization figures for the warmth pump, I at the moment haven’t any simple method to break down what was on the evening charge versus day. So I’ve used the annual common cut up in our payments for this (64% Day, 36% Night time). This must be the worst case situation as the warmth pump is biased to run over evening greater than via the day.
Whole Annual Heating & DHW Vitality Utilization – 5,345 kWh / £732.05
Month-to-month Common – 445 kWh / £61.00
Day by day Common – 15 kWh / £2.01
It’s value mentioning that I started recording this information round 6 months after we moved in. Don’t be disheartened if you’re seeing excessive power prices together with your warmth pump and also you’ve simply completed constructing, as typically power consumption could be larger 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 appropriate hand column within the desk beneath for our breakdown.
When it comes to single days, the best power 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 Vitality Utilization & Prices
The desk and graph beneath exhibits our whole power used final yr in kWh, damaged down into 2 values, separating the power mentioned above that was utilized by the warmth pump for house heating and scorching water, from the whole lot 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 dwelling 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 power consumption (rattling that PS4).
So listed here are the power consumption figures for the primary full yr within the new Automated Dwelling;
Whole Annual Vitality Utilization – 16,276 kWh / £2,273.60
Month-to-month Common – 1,356 kWh / £189.47
Day by 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 scorching water, all our cooking and washing, all our Lighting and leisure plus our ‘gasoline’ for the Electrical automotive.
Comparisons to Final Home
The newest figures I may discover confirmed that 68% of properties in Northern Eire use oil as their major methodology of heating (and amazingly 72% nonetheless use strong gasoline as a secondary methodology). In our earlier dwelling, 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 analogous measurement, 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 previous payments they usually present we averaged 5 x 900 litre fills of heating oil every year. In power 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 Vitality 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 are 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 evening and day, in each room, we all the time have scorching water on faucet. It’s exhausting to quantify the standard of life enchancment this brings. Stepping onto heat tiles on a rest room ground within the morning is fairly, fairly good.
Maybe extra importantly, we’ve decreased our whole power consumption by greater than 70%, together with all of the related CO2 financial savings and air high quality enhancements (try this information from our Airthings Wave Plus).
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 which means 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 (supply). Actually our bias for operating the heating at evening, coupled with the extraordinary ranges of spare wind power 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 might be no main surprises any time quickly. Nevertheless, upkeep is the one facet of the equation that we’ve no information on and it must be thought of.
A number of the damaging 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 number of days a yr to defrost itself however typically the effectivity of the system is excellent (and we’ve seen temperatures as little as -6 to date).
Comply with Jan Rosenow for some nice factual info on warmth pumps and the power transition typically.
I’ve been gathering the information for this put up during the last 12 months and the final third of 2021 noticed unbelievable power 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, it will finish in the summertime.
We needed to reduce our Photo voltaic PV plans through the construct to remain inside finances, however we hope to purchase a system, maybe this yr, to attempt to off-set a few of these value rises. As soon as put in, prices for the brighter months must be considerably decreased. A buddy’s close by 4kWp system produced 524 kWh in June 2021 for instance, which (assuming the identical 87% self-consumption charge as our earlier dwelling) would have virtually halved our invoice for that month from £164 to round £86.
A home battery continues 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 power 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 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 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 the moment affords 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 are usually not 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 Dwelling. A lot 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 power 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 dwelling with infinite scorching 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 critical 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 try our Instagram to observe the venture, 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.