Earth Notes: Saving Electricity and Gas (2021)

Updated 2021-05-02 10:20 GMT.
By Damon Hart-Davis.
Meter readings and energy-saving notes for dual fuel use at home in 2021.
Screenshot 20210118 System Admin Login Only legacy system closed
2021 PV Output
Meter readings and analysis of our electricity and gas carbon footprint at home in 2021.


See the daily PV generation logs for 2021 as .csv and .png chart.

2021-02: Beast From the East II

20210211 demand around evening peak in coldest part of February 20210219 demand around evening peak in coldest part of February

A view of demand from Feburary 2021 when "Beast From the East II" arrived, with high gas consumption days (eg >40kWh/d, 13th) between the 6th and the 15th.

The heating is off from 4pm to 7pm, and the house coasts thermally then. The only heavy load that routinely happens in that slot (we avoid washing and dishwashing for example) is cooking with induction hob and fan oven.

2021-04: April Swerves

The central heating was off for the whole of April other than a couple of specific events...

20210413 16WWmultisensortempL
Reheating the home after a few days with most people away (7.7kWh to raise house temperature 3.5°C).
20210429 16WWmultisensortempL
Impulse heating test to characterise one room better (5s, 13.0kWh over 7.2h).
2021 Fuel Consumption Data
MonthConsumed kWh (/d)Generated -kWh (/d)Consumed kWh (/d) PeriodNotes
2021-01 243 (7.8/d) -53 (-1.7/d) 592 (19/d) 20201231T18:13Z to 20210131T18:17Z (31d) Meter readings: electricity generation 52.7kWh, export 5.8kWh, import 196.4kWh (thus net consumption (I+G-E) 243.3kWh, self consumption ((N-I)/N) 19%); gas ~53.3m^3 (so 592kWh @ 11.1kWh/m^3).
Record high electricity consumption possibly in part from extra use of dehumidifier in kids' bedrooms (which could really do with their own MHRV), and national lockdown so more of everything including dehumidifier. Undoing lockdown gross consumption lift of ~20% would get us back to 6.5kWh/d, a far more reasonable winter figure!
Allowing ~4kWh/d for DHW, space heat is ~1.9kWh/HDD12 vs 2.6 last January. Warm bodies at home and the dehumidifier will have reduced space-heat demand, along with having most Radbots on 2 (17°C) rather than 3 (19°C).
HDD12=241 vs 142 last January.
2021-02 226 (8.1/d) -127 (-4.5/d) 464 (17/d) 20210131T18:17Z to 20210228T18:18Z (28d) Meter readings: electricity generation 126.7kWh, export 48.2kWh, import 147.3kWh (thus net consumption (I+G-E) 225.8kWh, self consumption ((N-I)/N) 35%); gas ~41.8m^3 (so 464kWh @ 11.1kWh/m^3).
Record high electricity consumption again, unfortunately. Both kids still doing school from home full time because of lockdown. There were some very high electricity consumption days (eg >10kWh/d, 7th) especially at the start of the month. Also high gas consumption days (eg >40kWh/d, 13th) between the 6th and the 15th (Beast from the East II). My son also has a new gaming PC...
From the 4th there is starting to be the tail end of PV generation at 4pm, taking the edge off peak-time consumption, alongside the battery. Mean daily PV generation was much the same as last February, but a bit lower than recent Februaries. Possibly pigeons taking to sitting on the panels, and a bit of snow, did not help.
HDD12=171 vs 128 last February.
2021-03 165 (5.3/d) -273 (-8.8/d) 450 (15/d) 20210228T18:18Z to 20210331T17:17Z (31d) Meter readings: electricity generation 272.8kWh, export 202.8kWh, import 99.3kWh (thus net consumption (I+G-E) 165.4kWh, self consumption ((N-I)/N) 40%); gas ~40.6m^3 (so 450kWh @ 11.1kWh/m^3).
Both children have been back at school since early (~8th) in the month, and so electricity gross consumption is back to a more normal 5.3kWh/d. The central heating was turned off at noon on the 29th, though we have a few cold days coming that may test us! (See next month's notes.)
Electricity imports were just under half of exports, ie 16WW switched to being net exporter this month. Also, by the end of the month (from the morning of the 29th onwards), some Enphase battery charge was lasting past midnight. In the (morning of) the 31st there was only ~1h fully discharged.
HDD12=138 vs 142 last March.
2021-04 168 (5.6/d) -512 (-17/d) 167 (5.6/d) 20210331T17:17Z to 20210430T17:16Z (30d) Meter readings: electricity generation 511.5kWh, export 380.4kWh, import 36.8kWh (thus net consumption (I+G-E) 167.9kWh, self consumption ((N-I)/N) 78%); gas ~15.1m^3 (so 167kWh @ 11.1kWh/m^3).
Note the dramatic increase in generation and self-consumption since March. Generation last April 536.0kWh from our 5.2kWp system, this April 511.5kWh, typical would be ~450kWh.
HDD was higher than March (and last April) but gas consumption down by ~10kWh/d, ie two-thirds lower. That saving of ~50kg of CO2 emissions is the force of of turning the central heating off entirely for a marginal month, and living with things slightly chilly.
Note that I did turn the heating on for about 90 minutes just before the family returned from a few days away at the cost of 7.7kWh.
I also did an impulse heating test of one room (13.0kWh) to get a better handle on its thermal behaviour.
HDD12=141 vs 61 last April.
~788 words.