Final August we took a have a look at a few of the selections that led us to construct a low power residence. Now that we’ve been by way of our first full calendar 12 months, it’s time to disclose our power invoice and see how issues are understanding. I’ve separated out figures for the warmth pump versus the whole lot else. However first a bit about our setup.
Economic system 7
As an all-electric home, it was vital to maneuver to an Economic system 7 meter which occurred a couple of months after we moved in. This offers us separate Day and Evening charges for our electrical energy. Sadly sensible meters should not accessible in Northern Eire but so there are presently no choices for half-hour metering, demand aspect response or agile tariffs.
The most effective factor we are able to do then is to ensure as a lot of our power 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 season Time.
All our electrical automobile charging is finished 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 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 reveals 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 strains right here characterize the quantity of power we used on the cheaper price, and it’s straightforward to identify the 5 nights that the EV was charged throughout this era.
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 put money into extra renewables. And as we’re working 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 below are the small print of our present mounted price tariff (together with VAT);
- Day Charge £0.1699 / kWh
- Evening Charge £0.0784 / kWh
- Standing Cost £3.54 / Month
On prime of the traditional 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 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 power monitor is round 725 Watts, however extra often the bottom line appears to sit down 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 try 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 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 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 so forth. Then the Clever Temperature Controller works within the background, grouping our rooms and UFH loops, controlling the stream temperature required as a way 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 stream 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 useful 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 building, tiled flooring and inner stone wall to launch the warmth in the course of the day. We now have experimented with a few of these methods during the last 12 months, tweaking issues to maneuver as a lot as attainable into the evening price, while sustaining consolation ranges in the course of 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 beneath the steps. There could also be just a little power within the ‘Every little thing Else’ a part of the info beneath, for the uncommon event that the system activates the immersion heater if the warmth pump can’t 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 might 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 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 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.
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, nevertheless it has proved to be very helpful.
Annual Heating & DHW Utilization & Prices
Whereas we’ve got actual power utilization figures for the warmth pump, I presently haven’t any straightforward approach 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% Evening). 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.
- Whole 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 declaring 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 usually 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 12 months. See the correct hand column within the desk beneath for our breakdown.
By way of single days, the very 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 reveals our whole power used final 12 months in kWh, damaged down into 2 values, separating the power mentioned above that was utilized by the warmth pump for house heating and sizzling water, from the whole lot 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 stay with us too (between home strikes). So we went from 2 adults to five in a single day, with all of the related additional power consumption (rattling that PS4).
So listed here are the power consumption figures for the primary full 12 months within the new Automated Dwelling;
| 2021 Month |
Warmth Pump |
Every little thing Else |
Whole kWh |
% 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% |
| Could | 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% |
- Whole 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
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 newest figures I may discover confirmed that 68% of houses in Northern Eire use oil as their major 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 outdated home was an analogous 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 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 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 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 at all times 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 got lowered 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). The truth is our bias for working 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 12 months elements guarantee (3 years labour) so hopefully there can be no main surprises any time quickly. Nonetheless, upkeep is the one facet of the equation that we’ve got no information on and it must be thought of.
Among 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 now have not seen any of those points. The pump might reverse on a couple of days a 12 months to defrost itself however typically the effectivity of the system is excellent (and we’ve seen temperatures as little as -6 thus far).
Observe Jan Rosenow for some nice factual data on warmth pumps and the power transition typically.
The Future
I’ve been gathering the info for this publish during the last 12 months and the final third of 2021 noticed unimaginable power 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, it will finish in the summertime.
We needed to lower our Photo voltaic PV plans in the course of the construct to remain inside finances, however we hope to purchase a system, maybe this 12 months, to try to off-set a few of these value rises. As soon as put in, prices for the brighter months ought 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 price as our earlier residence) would have virtually halved our invoice for that month from £164 to round £86.
A home battery continues to be an attention-grabbing choice too, both to retailer photo voltaic manufacturing or purchase cheaper electrical energy at evening to be used in the course of the day. As power 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 can be an ethical crucial to try to additional scale 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 discuss receiving £400 a month from their RHI scheme as an incentive to purchase a warmth pump. Nonetheless, Northern Eire presently gives no such assist to encourage householders to do the correct factor. Let’s hope issues change right here within the close to future
Success
It’s vital 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 consultants we employed – Daly Renewables and Epitome Residing. 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 power 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 snug residence with countless sizzling water, for round half the working 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 have 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 comply with the undertaking, 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.