Our house originally came with a SMETS1 smart meter, but for years, we treated it like a regular dumb meter — paying a flat rate for electricity and not really caring when we used it. If that sounds familiar, you might be in for a surprise when you see how our average electricity import costs changed over time.
To make sense of our energy journey, I’ve broken it into four overlapping phases, each focusing on a different strategy for optimising costs and usage:
- Phase 0 — Establishing Baseline Usage
- Phase 1 — Maximising Self-Consumption
- Phase 2 — Load Shifting
- Phase 3 — Maximising Export
Phase 0 — Establishing Baseline Usage
To measure the impact of the improvements made to our house, we first established a baseline.
Overall, our energy habits remained very consistent all the way from 2018:
- Gas central heating was highly dependent on outside temperatures (obviously).
- Indoor target temperature of 21.5°C.
- Consistent hot water demand throughout the day for a family of four (please note hot water estimation based on summer months).
- Small variations in electricity usage throughout the year.
- Increasing car mileage post-COVID.
The cost trend was clearly upward starting from late 2021 when energy prices started creeping up, culminating in the energy cost crisis caused by Russia’s war against Ukraine.
Please note that the cost calculations during the energy crisis use the price cap rates applied to our standard tariff, not the much higher wholesale prices at the time.
Key takeaway: before making changes, our energy costs were predictably rising — so anything that could stop it was worth exploring.
Phase 1 — Self-Consumption (November — September 2023)
Without an export tariff for almost five months, I focused on maximising self-consumption of the ‘free’ energy we were generating.
With the first month spent on getting familiar with the solar & battery system, we only really kick-started changes to our energy usage in December 2022. We then moved to a Smart Export Guarantee (SEG) tariff, paying 4p/kWh, but that was still much lower than any import rates until September 2023.
With such low export rates, I obsessed probably too much trying to use as much of the solar energy we were generating. This reached its peak in June 2023:
- 87% self-consumption (730kWh) of generated energy (835kWh).
- 85% self-sufficiency (only 60kWh imported at home, plus 70kWh at Tesla Superchargers).
- Powered the entire house, hot water, heating/cooling, and drove 1285 miles.
- All for just £32.58 (excluding standing charges).
Key takeaway: would I recommend this extreme self-sufficiency approach with significant behavioural changes and advanced Home Assistant automations to the average person? Most likely not. But it was a fascinating experiment and highly satisfying to pull off.
Phase 2 — Load Shifting (January 2023 — Onwards)
After approximately two months of having the solar & battery system in place, we switched from a flat rate to time-of-use tariff. This meant the off-peak electricity was dramatically cheaper than standard or peak rates, incentivising moving all shiftable load to the late night/early morning off-peak period.
Over time, we successfully shifted more than 95% of usage to off-peak for the following:
- Dishwasher (despite no built-in functionality to delay the cycle, we used a smart plug instead).
- Tumble dryer (with built-in timer feature).
- Immersion heater for hot water (scheduled via a Wi-Fi switch).
The impact was immediate — our average import rate dropped off a cliff in early 2023. If you look at the cost graph, you can practically see the moment we said goodbye to flat-rate pricing:
Key takeaway: this is where having a smart meter became incredibly useful. Not because of the in-home display (which mostly exists to remind you that putting on an oven or boiling a kettle costs money), but because it unlocked access to time-of-use tariffs. Thanks to those, our average unit cost dropped below pre-energy-crisis levels.
Phase 3— Maximising Export (September 2023 — Onwards)
In September 2023, Octopus switched us from the SEG tariff (paying 4p/kWh) to the Outgoing tariff (paying 15p/kWh). Making off-peak electricity cheaper than export, had a very substantial impact:
- Simplified Home Assistant automations — no more complex solar-diversion logic or predictive battery charging.
- Easier car charging experience — just plug it in for the night, rather than trying to look at the weather forecast for upcoming days.
- Further load shifting — now from solar to off-peak, prioritising off-peak charging and exporting excess solar.
- More financially viable solar PV & battery systems — with more credit accumulated during summer months.
Key takeaway: this approach aligned with wholesale electricity prices, where night-time is usually cheapest and evening peaks are most expensive. A win-win for both our wallet and the grid!
Final Thoughts on Tariffs
Despite common misconceptions, time-of-use tariffs and smart meters aren’t just gimmicks. They have the potential to radically reduce energy costs while allowing for smarter energy use. By shifting consumption to off-peak hours and making the most of lower rates, we can use more energy for less money.