Understanding the electricity emission factor and its role in energy renovation
Emission factor: a simple definition and the units to know (gCO2e/kWh) to talk straight to clients
The emission factor is the number of grams of CO2 equivalent emitted to produce 1 kWh of electricity consumed. The unit to remember is gCO2e/kWh. It's used to translate an energy gain into a climate gain. With it, you can explain, backed by numbers, the impact of insulation or a heat pump, without embellishing the story.
Why it varies by hour and season: electricity mix, peak demand, load shedding
This factor moves because the electricity mix changes continuously. During peak hours, especially in winter, the grid may call on higher-emission sources. Conversely, when wind, hydro or solar cover demand, carbon intensity drops. Load shedding and control (water tank, heating) allow some usage to shift toward more favourable hours.
Where to find reference values and how to cite them in your files (2026)
For an "official" value in 2026, rely on the DESNZ conversion factors (annual averages). For an hour-by-hour approach, use the published carbon intensity data for the GB grid. In your files, state the source, the year, the scope (UK, average, CO2e) and the unit gCO2e/kWh. This avoids misleading comparisons.
Renewable electricity: how it does (or doesn't) lower the emission factor
Renewables and the electricity mix: what actually matters (hydro, wind, solar, biomass)
The electricity emission factor drops when the mix reduces reliance on fossil-fuel plants. Hydro provides dispatchable production. Wind and solar lower the average during their hours, but if the grid falls back on gas or coal as backup, the real gain shrinks. Biomass can help, if the resource is well managed and the plant is well utilized.
Difference between contractual "green electricity" and electricity actually consumed on the grid
A "green electricity" offer often relies on guarantees of origin. You're funding renewable production, but the electricity you consume remains whatever is on the grid at that moment. Without new generation capacity, the physical mix doesn't change instantly.
Storage, load control and self-consumption: where the effect is clearest
The effect is clearest when you cut your kWh usage during the most carbon-intensive hours. Solar self-consumption, a controlled hot-water tank, scheduled EV charging, or a battery that shifts midday energy to the evening. Storage and load control cut the peak, exactly when the emission factor climbs.
Concrete impact on your equipment choices: heating, hot water and electrical uses
Heat pumps and the emission factor: how to make the case without getting it wrong
A heat pump reduces heating kWh thanks to its real COP. To talk CO2, rely on an official electricity emission factor and clearly state whether it's an annual average. Avoid the shortcut of "carbon-free electricity." Your message fits in one sentence: fewer kWh consumed, so fewer emissions, provided the heat pump is properly sized.
Heat-pump water heater, radiators, mechanical ventilation, cooking: prioritizing loads based on available electricity
Before changing equipment, look at the subscribed power and usage peaks. A heat pump and a heat-pump water heater draw harder at startup. Electric radiators add up quickly. Mechanical ventilation uses little power but runs continuously. On the cooking side, power draws are short but high. Prioritize whatever avoids peaks, with time-of-use control where possible.
Photovoltaic self-consumption: when it improves the footprint and when the effect is limited
Photovoltaic mainly helps with daytime consumption. It improves the footprint if you self-consume, for example DHW at midday, appliances, EV charging. The effect is more limited for winter heating, since production drops just as needs rise. A bit of DHW storage or simple load control often works better than a large battery.
Properly calculating and justifying the CO2 gain in your documents (assessment, EPC, quote)
Simple calculation method: electric kWh × emission factor = kgCO2e (with job-site examples)
First calculate the electric kWh avoided over a typical year, based on usage (heating, hot water, auxiliaries). Then apply the official emission factor for the electricity mix (DESNZ). Job example 1: replacing electric panel heaters with an air-to-air heat pump. Before: 6,060 kWh/year, after: 2,000 kWh/year, gain: 4,060 kWh/year. With an annual factor of around 0.21 kgCO2e/kWh, that's roughly 850 kgCO2e/year. Job example 2: hot water heat pump. Gain of 900 kWh/year, or about 190 kgCO2e/year under the same assumption.
Avoiding classic mistakes: annual vs. marginal factor, usage assumptions, double-counting solar
Stay consistent with your conventions. The EPC and retrofit assessments rely on an average annual factor, not the marginal one (more useful for load-shedding analyses). Document your usage assumptions (setpoint temperature, occupancy, hot water). For photovoltaic, don't double-count. Only self-consumption that reduces grid kWh should be counted, without adding production and bill savings together.
Ready-to-use wording for your reports: clarity, transparency, traceability (2026)
- Assumptions used. Standard EPC consumption or assessment scenarios. Electricity emission factor from the DESNZ tables, with version and consultation date specified (2026 update). To frame your documents, you can also rely on the new EPC rules and their impact on renovation.
- Calculation. CO2e gain = (electric kWh before - electric kWh after) × emission factor. Converted to kgCO2e/year.
- Limits. Estimated results, dependent on actual usage and weather. Source data archived (screenshots, product sheets, readings).
What 2026 changes for your projects: trends, client expectations and best practices
Grid and renewables developments: what to anticipate on the ground in 2026
In 2026, demand for solar self-consumption and load control is rising. On site, the challenge is to secure the electrical system when power draws add up (heat pump, water tank, EV charging). Think sizing, protections, surge arresters and spare capacity in the panel. And anticipate connection lead times with a complete application.
Whole-house renovations: how to integrate electricity into a coherent package (insulation, ventilation, controls)
Large-scale renovations push you to treat the whole building as a system. Good insulation changes the needs, ventilation prevents moisture issues, and controls stabilize comfort. Your electrical package must prepare dedicated supplies, control wiring and simple load control, without overengineering it.
Checks and compliance: securing your files and your pitch (certification, funding, supporting documents)
The funding schemes in 2026 remain demanding. Even if the electrical work isn't always a funded measure on its own, it must be consistent with the funded work overall. Lock down BS 7671 compliance, the electrical installation certificate and the Part P notification where needed, and keep clean evidence. Detailed quotes, technical data sheets, before/after photos and traceable references, this avoids rejected applications and unpaid invoices.
