Resilience Value of Lost Load Calculator
Value of Lost Load (VoLL) is the standard framework utilities, regulators, and grid planners use to quantify the economic cost of an outage -- the dollar value per kilowatt-hour of energy a customer cannot use when the power is out. This calculator applies that same framework to a specific facility to size the actual dollar value a microgrid or backup system delivers by avoiding that lost load, which is often far larger than the direct energy savings alone. It estimates the value of lost load per event and the annual resilience value from the facility type, the VoLL rate, the critical load at risk, the expected outage frequency, and the average outage duration. It pairs naturally with our Microgrid Payback Period Calculator for folding this resilience value into a payback analysis, and our Critical Load Backup Sizing Calculator for determining which loads are genuinely critical.
Selecting a preset auto-fills the VoLL field below with the midpoint value shown, but the field stays editable.
The economic cost, in dollars per kilowatt-hour, that the customer incurs when power is unavailable. Presets use midpoint values from published VoLL studies; substitute a site-specific figure if you have one.
The load that would actually go unserved during an outage -- typically just critical and priority circuits, not the facility's full peak demand.
How many outages of this kind the facility expects in a typical year. Facilities in wildfire-prone PSPS territories may see several multi-day events per fire season.
The average duration of a single outage event. Common outages last a few hours; PSPS and storm-driven events commonly last 24-72+ hours.
annual energy at risk (kWh) × value of lost load ($/kWh)
energy at risk per event (kWh) × value of lost load ($/kWh)
energy at risk per event (kWh) × expected outage frequency (events per year)
critical load at risk (kW) × average outage duration (hours)
Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.
How we calculate this →Value of Lost Load is the framework utilities, regulators, and grid planners use to quantify the economic cost of an outage -- and applying it to a specific facility often reveals that the resilience value a microgrid or backup system delivers is far larger than its direct energy savings alone. At the defaults (a commercial facility at $20/kWh VoLL, 100 kW of critical load, two 6-hour outages per year), the avoided disruption is worth $24,000 per year -- a number that never appears on a utility bill but is frequently the real justification for investing in backup power at a critical facility.
How this is calculated
This calculator applies the Value of Lost Load (VoLL) framework to a specific facility to estimate the dollar value of the energy an outage would leave unserved, from the facility type, the VoLL rate, the critical load at risk, the expected outage frequency, and the average outage duration. Four quantities tie the calculation together.
Energy at Risk per Event (kWh) = Critical Load at Risk (kW) × Average Outage Duration (hours). The critical load at risk is the power the facility would actually lose during an outage -- typically just critical and priority circuits, not the full peak demand. Multiplying that load by the average outage duration gives the energy that goes unserved in a single event. At the defaults (100 kW and 6 hours), that is 100 × 6 = 600 kWh.
Annual Energy at Risk (kWh) = Energy at Risk per Event (kWh) × Expected Outage Frequency (events per year). The outage frequency is how many outages of this kind the facility expects in a typical year. Multiplying the per-event energy by the annual event count gives the total energy at risk across the year. At the defaults (600 kWh and 2 events/year), that is 600 × 2 = 1,200 kWh.
Value of Lost Load per Event ($) = Energy at Risk per Event (kWh) × Value of Lost Load ($/kWh). VoLL represents the economic cost per unit of unserved energy -- the dollar value of lost production, spoiled inventory, safety risk, and other consequences beyond the electricity itself, which is why it is typically many times higher than the retail price of electricity. Multiplying the per-event energy at risk by the VoLL rate gives the dollar loss from a single outage. At the defaults (600 kWh and $20/kWh), that is 600 × $20 = $12,000.
Annual Resilience Value ($) = Annual Energy at Risk (kWh) × Value of Lost Load ($/kWh). Multiplying the total annual energy at risk by the VoLL rate gives the total dollar value of the disruption a microgrid or backup system would avoid over a year -- the resilience benefit that, unlike direct energy savings, does not show up on a utility bill but is often the real justification for investing in backup power. At the defaults (1,200 kWh and $20/kWh), that is 1,200 × $20 = $24,000.
Two notes on the model. First, the VoLL rate is a single representative figure, appropriate for a planning-level estimate of resilience value -- but published VoLL studies (e.g. from DOE and Lawrence Berkeley National Lab interruption cost estimator work) show wide ranges depending on outage duration, time of day, and warning time, and VoLL varies enormously by customer type (a residential outage mostly costs inconvenience and some spoiled food, while a hospital outage risks patient safety directly), so the facility type preset auto-fills a midpoint value while keeping the field editable for a site-specific figure. Second, this calculator reports the dollar value of avoided lost load only and does not model the cost of the backup system itself (see the Microgrid Payback Period Calculator and Microgrid vs. Grid-Tied Cost Comparison Calculator for cost context), the probability distribution of outage duration and frequency rather than average figures, load shedding strategies that reduce the critical load at risk as an outage progresses, the indirect and reputational costs of repeated outages (customer churn, contract penalties, insurance premiums), or the effect of advance notice on how much loss can actually be mitigated through preparation -- all of which a full resilience planning evaluation would include. Data sources: residential VoLL of roughly $5/kWh, commercial VoLL of roughly $20/kWh, industrial VoLL of roughly $35/kWh, and hospital/critical-facility VoLL of roughly $75/kWh from published VoLL studies and DOE/Lawrence Berkeley National Lab interruption cost estimator work; VoLL varying widely by outage duration, time of day, and warning time from the same sources. Verification: with defaults ($20/kWh VoLL, 100 kW critical load, 2 events/year, 6 hours/event), Energy at Risk per Event = 600 kWh, Annual Energy at Risk = 1,200 kWh, Value of Lost Load per Event = $12,000, Annual Resilience Value = $24,000.